LIA Members only. For use by
THE LIGHT SOURCE GUIDE.
LIA Copyright © 2017. All information stated within this brochure is correct at time of publication – Jan 2017. www.thelia.org.uk
CONTENTS
INTRODUCTION
LEGISLATION
LIGHT
LAMP HISTORY
LAMPS
INCANDESCENT
LIGHT EMITTING DIODES (LEDS)
FLUORESCENT LAMPS
HIGH INTENSITY DISCHARGE
INDUCTION LAMPS
NEW AND UNUSUAL LAMP TECHNOLOGIES
LAMPS AND THE ENVIRONMENT
FAQS
GLOSSARY
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INTRODUCTION
The Lighting Industry Association (LIA) is a trade association representing UK manufacturers and importers of lighting equipment. LIA members design, manufacture and sell electric lamps,luminaires, lamp-holders, low-voltage lighting, emergency lighting, road lighting, control gear and equipment associated with lighting, throughout the European Union (EU) and worldwide.
Most lamp types associated with general lighting within and around buildings can be used in various applications. Consequently, this guide focuses more on how the lighting is generated and not by end usage, although typical applications are given.
The Light Source Guide aims to provide an introduction to the key lamp types available, with the objective of providing as much information as possible for the reader, whether they are new to lighting or even an experienced engineer or designer.
Detailed information about individual lamps is available from lamp manufacturer members of the Lighting Industry Association.
With the global concern over carbon emissions and global warming, the key driving factor in the development and use of light sources is Energy Efficiency.
Energy efficient technology is seen to play an important role in the future approach to energy both in the short and medium to long term. According to the European Commission by 2010 about 180 million tonnes of CO2, the equivalent annual output of around 50 power stations, could be prevented by the use of energy-efficient products and appliances alone in Europe -around half of the EU’s commitment under Kyoto.
More than 50% of all lamp technologies installed in Europe are still not the most energy efficient; as such the potential for improvements and savings (of energy, costs and CO2 emissions) for Europe are significant.
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LEGISLATION
Lighting is affected by a wide range of regulations and legislation that have been set by the European Union (EU) and the United Kingdom (UK). A large proportion of UK legislation has been created by over- arching EU Directives and Regulations, some of which may have their origins in International agreements. This guide looks at the legislation that most directly applies to lamps. These rules and regulations relate largely to environmental issues including energy use, waste and recycling, hazardous substances and labelling. In addition electrical safety, optical hazards and electromagnetic interference are also covered.
The legislation landscape affecting products is constantly being updated, revised and recast in order to maintain both consistency of intent and relevance to advances in technology. As a result this guide seeks to point the reader towards the relevant documents and references rather than provide a detailed explanation of each. It is the responsibility of all manufacturers, suppliers, importers and distributors to familiarise themselves with the detailed obligations they are obliged to meet under any relevant legislation.
The lighting industry and the LIA, as a representative body, are committed to the development and introduction of quality lighting products that meet all relevant national and international legislation.
Definition
For the purposes of this guide a lamp is any product that can be fitted to a recognised standard lamp socket and includes those with integrated electronics.
Background information and summary of relevant legislation
It is estimated that lighting consumes about 18% of the electricity generated in the UK. As a result there is considerable emphasis placed on encouraging the use of more efficient lighting products as well as better control of its use within commercial and domestic applications. However, the importance of light in terms of well-being, and other human factors, means that any efficiency gains must not be at the expense of the quality of light delivered. Lamps directly affect the performance and characteristics of lighting and, as such, are covered specifically by a number of rules and regulations. These can be considered under a number of distinct subject headings:
• Energy and CO2 emissions reduction • Health • Safety & EMC • Environmental issues
There is a degree of overlap between some of these headings and the guide will highlight any legislation that covers more than one of these headings.
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Energy and CO2 emissions reduction
Much of the recent legislation that is relevant to lighting is concerned with the reduction of energy use linked to the lowering of CO2 emissions. Initially the focus has been on ensuring products are as efficient as technically and practically possible, although there is now some recognition that controlling the use of energy consuming products is also important. Legislation covers both the energy performance of the various products and how the public is informed about the performance through labelling and required technical descriptions.
The most relevant directives, regulations and implementing measures directly affecting lamps are:
• The EcoDesign Framework Directive – 2009/125/EC • Commission Regulations (or ‘implementing measures’ within 2009/125/EC) - EU 1194/2012 – Directional lamps, LEDs and related equipment - EC 245/2009 (as amended by EU 347/2010) – Fluorescent lamps, HIDs, and ballasts and luminaires able to operate such lamps - EC 244/2009 – Non-directional household lamps. (As amended by EC 859/2009 concerning the UV radiation of non-directional lamps) - The Energy Labelling Directive – 2012/30/EU; as supplemented by Commission Delegated Regulation (EU) No. 874/2012 - EU 2015/1428 amending 244/2009, 245/2009 & 1194/2012.
Summary information and tables are included in this guide, particularly where clarification or explanation is required.
Health
LightingEurope have produced the following guides that cover the current EU Directives and Regulations that refer to all the relevant aspects of photobiology, light and health:
• Human Centric Lighting: Beyond Energy Efficiency – LightingEurope, July 2013; • Photobiological Safety in Lighting Products for use in Working Places – LightingEurope, February 2013
Safety & EMC
Lighting is also affected by wider legislation concerning safety, particularly that which refers to electrical products. The development of ‘low energy replacement lamps’, initially using fluorescent and now solid state (LED) technology has introduced electrical and electronic components into main stream lamps. The most relevant measures are:
• Low Voltage Directive – 2014/35/EU • EMC Directive – 2014/30/EU • Radio Equipment Directive (RED) – 2014/53/EU
The LVD largely focusses on the electrical safety of products, while the EMC Directive addresses the issues of electromagnetic interference potentially occurring between electronic devices. The RED covers any product which uses radio communication (wifi, Bluetooth etc) and includes requirements for LVD and EMCD.
All products covered by the scope of these Directives must have supporting documentation to demonstrate their compatibility. Meeting these criteria is also mandatory under the CE marking scheme.
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Environmental issues
The manufacture of lighting and electronic products involves the use of a wide range of materials and substances, some of which are now controlled by legislation concerning the use of hazardous substances. In addition there is legislation covering the treatment of ‘end of life’ products which has an impact on the lighting industry, both in terms of the disposal of lamps and luminaires.
The most relevant measures are:
• Waste Electrical and Electronic Equipment (WEEE) Directive 2012/19/EU • Restriction of Hazardous Substances (RoHS) Directive 2011/65/EU
Both of these directives are covered by UK Statutory Instruments – The Waste Electrical and Electronic Equipment Regulations 2013 and The Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment Regulations 2012.
CE Marking
Virtually all products made in, or entering, the European Union market, are required to be CE Marked under the CE Marking Directive 93/68/EEC. The CE mark is the manufacturer’s self declaration that any given product conforms to all the relevant EU Directives applicable to its manufacture and function.
All lamps are subject to at least one of the Directives identified above and must, therefore, be CE marked. As a result for each lamp it is required that its manufacturer holds a Declaration of Conformity and a Technical File that demonstrates compliance with all the relevant directives and the applicable harmonised standards.
Commentary and clarification
All of the EU Directives, Commission Regulations and UK Statutory Instruments mentioned above are readily available as free downloads from the relevant EU and UK Government websites. In the following section the guide provides additional information and clarification of key parts of the legislation directly affecting lamps.
The EcoDesign Framework Directive for Energy Related Products – 2009/125/EC The EcoDesign Directive covers a wide range of energy using and related products including lighting. Its intention is to force the phase-out of products that are less energy efficient in favour of new, more efficient technologies. This is a re-cast of Directive 2005/32/EC which was generally known as the ‘Energy Using Products Directive’.
The Energy Related Products Directive sets a framework for the management of a listed range of products from design to ‘end-of-life’ and covers all aspects of the process with regard to embedded energy as well as energy consumed in use. Lighting is in the list of energy related products, but there are no other direct references; all details of the specific lighting products affected are found in the related Commission Regulations – or ‘implementing measures’.
Commission Regulations (or ‘implementing measures’ within 2009/125/EC)
EC 244/2009 – Non-directional household lamps. (As amended by EC 859/2009 concerning the UV radiation of non-directional lamps.) Often referred to as ‘Domestic Implementing Measures – Part 1’, this regulation is responsible for the phasing out of the ubiquitous GLS incandescent lamp over a number of years, from September 2009 on. The regulation included an automatic review that had to be undertaken 5 years after it came into force in April 2009. This review is currently being carried out.
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Table 1: Original timetable for phasing out inefficient lamps as set down in EC 244/2009, summarised to show the impact of the regulation.
Clear Lamps
Stage Date Lamps phased-out Replacements
1 1 Sept 2009 > 950 lumens (≈ 80W GLS) Energy class C or above
2 1 Sept 2010 > 725 lumens (≈ 65W GLS) Energy class C or above
3 1 Sept 2011 > 450 lumens (≈ 45W GLS) Energy class C or above
4 1 Sept 2012 > 60 lumens (≈ 12W GLS) Energy class C or above
5 1 Sept 2013 Improved quality requirements Energy class C or above
Review 2014 - -
6 1 Sept 2016* All clear lamps > 60 lumens Energy class B or above
Non-Clear Lamps
Stage Date Lamps phased-out Replacements
1 1 Sept 2009 All non-clear (pearl type) lamps Energy class A
* Regulation 2015/1428 extends the date to 01/09/2018
Note
The regulation excluded a number of ‘special purpose’ lamps. These included incandescent oven / refrigerator lamps and rough service lamps. Regulation 2015/1428 has updated these requirements
The regulation contains a number of tables that define the exact criteria to determine the performance of those lamps that are to be phased out. In addition there is considerable detail about the performance and life of acceptable low energy replacements. Recognising that the widespread introduction of low energy lamps into the domestic market requires the consumer to be properly informed, the regulation also sets down the information that must be provided on the lamp packaging plus further data that must be publicly available on free access websites.
Amending Regulation EU 2015/1428 has delayed Stage 6 until 1 Sept 2018. It also closed the loophole which allowed lamps marked as “rough service” or “industrial use” etc to be sold as special purpose.
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EC 245/2009 (as amended by EU 347/2010) – Fluorescent lamps, HIDs, and ballasts and luminaires able to operate such lamps. This regulation, also referred to as ‘Tertiary Implementing Measures’, is aimed at improving the energy performance of lighting in the non-domestic market. The measures detailed in the regulation are to be implemented in stages according to the timetable shown in Table 2 below.
Table 2: Timetable of the planned implementation stages
Stage Implementation date
1: One year after entry into force 13th April 2010
Intermediate:18 months after entry into force 13th October 2010
2: Three years after entry into force 13th April 2012
Intermediate: Six years after entry into force 13th April 2015
3: Eight years after entry into force 13th April 2017
As indicated in the regulation’s title these measures cover fluorescent lamps, HIDs (high intensity discharge lamps) and ballasts and luminaires. Reflecting the broad range of light sources the regulation contains a great deal of detail on the performance criteria to be met by these lighting products at each stage of implementation.
The addition of the amendment EU347/2010 widened the scope of the tertiary lighting implementation measures to include fluorescent and HID control gear. This also repealed the Ballast Directive 2000/55/EC.
Amending Regulation EU 2015/1428 has updated tables 13 and 14.
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EU 1194/2012 – Directional lamps, LEDs and related equipment. Alternatively known as ‘Domestic Implementing Measures – Part 2’, this regulation covers lamps that are, arguably, as common in the tertiary sector as they are in the home. The regulation details the energy efficiency criteria to be achieved (by the light sources covered) in the following stages:
Table 3: Timetable of planned implementation stages.
Stage Implementation date
1 1st September 2013
Intermediate 1st March 2014
2 1st September 2014
3 1st September 2016
The regulation includes incandescent, fluorescent, HID and LED light sources and defines the energy efficiency index (EEI) they must meet by each stage. In addition the regulation also defines certain qualitative criteria that LED light sources must achieve e.g. colour rendering and life, because there is perceived to be a need to ensure that this technology is seen to be a valid replacement for more established light sources.
The scope of this regulation covers:
(a) directional lamps; (b) light-emitting diode (LED) lamps; (c) equipment designed for installation between the mains and the lamps, including lamp control gear, control devices and luminaires (other than ballasts and luminaires for fluorescent and high-intensity discharge lamps); including when they are integrated into other products.
Due to the fact that the regulation includes directional light sources it also contains definitions of how the light output of such sources is to be assessed and measured. As in the other implementing measures set out under the overall Eco-Design requirements the regulation also determines the extent of documentation and labelling required.
There are a number of guides to the detailed technical requirements of EU1194/2012 and the one prepared by LightingEurope.
Amending Regulation EU 2015/1428 has updated the special purpose requirements, added new requirements on lamp/luminaire compatibility and updated requirements on lamps that can be packed with luminaires.
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Labelling
Although there are requirements within the above implementing measures for products to be accompanied by specific information and labels there are some additional Directives that determine the design and content of energy and performance labels. Some of these are mandatory while others are, in effect, optional.
Framework Directive 2010/30/EU (Energy Labelling)
This Directive is the ‘framework’ that governs the indication by labelling and product information about the consumption of energy and other resources by energy-related products. It should, therefore, be studied alongside the EcoDesign Framework Directive, and its related implementing measures. While this Directive covers all products falling within the Commission’s definition of ‘energy-related products’ there are a number of specific Delegated Regulations that are either specific to lighting products or contain specific lighting sections.
Commission Regulations (or ‘implementing measures’ supporting 2010/30/EU)
Commission Delegated Regulation 874/2012/EU with regard to energy labelling of electrical lamps and luminaires
The scope of this regulation covers the following lighting products:
a. Filament lamps b. Fluorescent lamps c. High intensity discharge lamps (HID) d. LED lamps and LED modules
The regulation also extends the scope into the labelling of any luminaires containing the above lamps as well as when they are integrated into other products, for example – furniture. The regulation also details a number of exceptions. The requirements of this regulation came into force on the 1st September 2013 with a few exceptions and some transitional arrangements.
All of the requirements are detailed in the regulation and it is from this document that the format of the energy label is set down:
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As can be seen the layout and content is 3 prescribed in some detail; all the numbered 0.8 mm 1.4 mm pointers refer to detailed design criteria. This
1.4 mm label has its origins in the earlier Directive 98/11/ 1 EC, which applied to certain Household Lamps 2 including incandescent and compact fluorescent types. 8 9 There are a number of label variations allowed 4 but these are still detailed in a similar manner. There are also labels designed for luminaires, 6 7 mm which give some additional information about 5 suitable lamp types. However, this regulation is not solely concerned with labelling the products; it also details the 75 mm technical documentation that supports the
5 mm information displayed on the label. The regulation also includes a table detailing the Energy Efficiency Index (EEI) for each class of lamp.
7
36 mm
Table 1: Original timetable for phasing out inefficient lamps as set down in EC 244/2009, summarised to show the impact of the regulation.
Energy efficiency index (EEI) Energy efficiency index (EEI) Energy efficiency class for non-directional lamps for directional lamps
A++ (most effiecient) EEI < 0,11 EEI < 0,13
A+ 0,11 < EEI < 0,17 0,13 < EEI < 0,18
A 0,17 < EEI < 0,24 0,18 < EEI < 0,40
B 0,24 < EEI < 0,60 0,40 < EEI < 0,95
C 0,60 < EEI < 0,80 0,95 < EEI < 1,20
D 0,80 < EEI < 0,95 1,20 < EEI < 1,75
E (least efficient) EEI > 0,95 EEI > 1,75
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Commission Delegated Regulation 518/2014/EU with regard to labelling of energy-related products on the internet
This regulation also falls under the scope of Directive 2010/30/EU and amends a number of previous regulations relating energy-related products including 874/2012/EU. In effect it extends the obligations of suppliers, manufacturers, importers and distributors to the information that must be made available on the internet. For each affected existing regulation that it amends it adds a new Annex that defines the minimum information and labelling information required. The new requirement must be met for all products put on the market with effect from 1st January 2015.
ECO Labelling There is a separate EU scheme covering the subject of ‘ECO Labelling’. This scheme is intended to demonstrate that a given product meets a number of sustainability measures covering energy use, embedded energy and raw materials used. The Commission Decision 1999/568/EC was the initial definition of the ecological criteria for lamps, and this was revised by 2002/747/EC. The most recent documents relevant to lamps are:
Commission Decision 2011/331/EU establishing ecological criteria for the award of an EU EcoLabel for light sources
This set down the detailed criteria that any submitted light source was required to meet in order to be awarded an EcoLabel. The scheme is not mandatory and the current criteria were due to expire on the 6th June 2013. However, Commission Decision 2013/295/EU extended the expiry date to 31st December 2014.
Hazardous Substances
The manufacture of modern, low energy, lamps involves much more complex processes and materials than those that were required for the incandescent GLS lamp. The introduction of discharge tubes – compact fluorescent (CFL) – involves the use of a number of chemicals including mercury. In addition both CFL and LED technology often requires that the lamp includes electronic components. As a result many lamps are subject to both the Waste Electrical and Electronic Equipment (WEEE) and the Reduction of Hazardous Substances (RoHS) Directives.
The WEEE Directive
The WEEE Directive 2002/96/EC entered into force in February 2003, but this has since been revised as the waste stream has grown. The new Directive 2012/19/EU entered into force on 13th August 2012 and became effective on the 14th February 2014. These directives introduced schemes to ensure that consumers were able to safely recycle electrical and electronic products free of charge. This places an obligation on suppliers / manufacturers to introduce recycling schemes to cater for these needs. In the UK the WEEE Directive has been transposed into UK law via the WEEE Regulations 2013, which became law on the 1st January 2014. (See Statutory Instrument 2013 No. 3113.)
More details of the WEEE Regulations can be found on the Health and Safety Executive (HSE) website.
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Reduction of Hazardous Substances (RoHS) Directives
Alongside the introduction of recycling schemes for WEEE products the EU also developed legislation to restrict the use of hazardous substances in these products. The RoHS Directive 2002/95/ EC requires the use of certain heavy metals, flame retardant chemicals and other materials to be replaced by safer alternatives. This Directive was revised as the RoHS recast Directive 2011/65/ EU and it became effective on the 3rd January 2013. The Directive was transposed into UK Law by Statutory Instrument 2012 No. 3032 Environmental Protection – The Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment Regulations 2012, which came into force on the 2nd January 2013 and requires CE marking from this date. The use of other RoHS logos is no longer allowed. www.gov.uk/rohs-compliance-and-guidance
As an indication of the close links between the WEEE and RoHS Regulations, there has been a further revision of the RoHS Regulations to align the Regulations. This has been done via Statutory Instrument 2014 No. 1771 Environmental Protection - The Waste Electrical and Electronic Equipment and Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment (Amendment) Regulations 2014.
Other measures that may affect lamps and lighting There are some important measures relating to broader energy use that also influence lighting but do not directly impact on its design and production. These are:
Energy Services Directive (ESD) 2006/36/EC
The purpose of the Directive is to make the end use of energy more economic and efficient by influencing the supply side of the energy market. It is intended to set a framework for the energy supply industry that encourages the use of energy efficiency measures and allows, for example, the use of energy performance contracts.
The Energy Performance in Buildings Directive (EPBD) 2010/31/EU
The overall objective of the EU Energy Performance of Buildings Directive is to:
‘Promote the improvement of energy performance of buildings within the Community taking into account outdoor climatic and local conditions, as well as indoor climate requirements and cost-effectiveness’.
Each EU member state was required to transpose the original Directive (2002/91/EC now re-cast as above) into law by the beginning of 2006 with a further three years being allowed for full implementation of specific articles.
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LIGHT
How Light is Generated
To understand how lamps work and hence select the right light source for a particular application, we need to understand how light is generated. Light is a form of energy that can be released by an atom. It is made up of many small particle-like packets that have energy and momentum but no mass. These particles, called light photons, are the most basic units of light.
Particles
1
Nucleus
2 3
Light Photon . A collision wit a mo ing particle e cites t e atom . T is causes an electron to ump to a ig er energ le el . T e electron all ac to its original energ le el releasing t e e tra energ in t e orm o a lig t p oton.
Atoms release light photons when their electrons become excited. Electrons are the negatively charged particles that move around an atom’s nucleus (which has a net positive charge). An atom’s electrons have different levels of energy, depending on several factors, including their speed and distance from the nucleus. Electrons of different energy levels occupy different orbits. Generally speaking, electrons with greater energy move in orbits farther away from the nucleus. When an atom gains or loses energy, the change is expressed by the movement of electrons. When something passes energy on to an atom, an electron may be temporarily boosted to a higher orbit (farther away from the nucleus). The electron only holds this position for a tiny fraction of a second; almost immediately, it is drawn back toward the nucleus, to its original orbit. As it returns to its original orbit, the electron releases the extra energy in the form of a photon, in some cases a light photon.
The wavelength of the emitted light (which determines its colour) depends on how much energy is released, which depends on the particular position of the electron. Consequently, different atoms will release different light photons. The colour of the light is determined by which atom is excited.
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Wavelength
Light sources emit radiation across the electromagnetic spectrum. Some of the radiation is emitted in the form of visible light. See below.
Wavelength, metres 10-14 10-12 10-10 10-8 10-6 10-4 10-2 1 102 104
Cosmic Ra Gamma Ra Ra Ultra iolet In rared Microwa e Radio
Wavelength, nm
The visible spectrum is a narrow band between 380 and 780 nanometres which can be detected by our eyes. The eye is able to discriminate between different wavelengths and the brain interprets this as colour. Violet and blue are situated at the shorter wavelength end of the spectrum, with reds occurring at longer wavelengths, and green/yellow at the centre. In order to develop energy-efficient lighting products, the most important goal of the lamp engineer is to concentrate as much energy as possible into this narrow visible band, while limiting the amount that is wasted in the invisible adjacent ultraviolet and infrared regions.
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Natural Light
In order to understand artificial light sources, we need to consider natural light, daylight, or SKYLIGHT. (Source SLL Guide 2009)
Skylight
Light from the sun is scattered by the atmosphere, and the distribution and amount of light received at ground level is dependent on atmospheric conditions. The International Commission on Illumination (CIE) categorise SKYLIGHT into a series of 15 sky distributions (BS ISO 15469:2004 Spatial distribution of daylight – CIE standard general )and give a formula that may be used for calculating the relative luminance distribution of the sky. The following list details the types of sky distribution:
Type Description of luminance distribution Number
1 CIE Standard Overcast Sky, Steep luminance gradation towards zenith, azimuthal uniformity
2 Overcast, with steep luminance gradation and slight brightening towards the sun
3 Overcast, moderately graded with azimuthal uniformity
4 Overcast, moderately graded and slight brightening towards the sun
5 Sky of uniform luminance
6 Partly cloudy sky, no gradation, towards zenith, slight brightening towards the sun
7 Partly cloudy sky, no gradation, towards zenith, brighter circum solar region
8 Partly cloudy sky, no gradation towards zenith, distinct solar corona
9 Partly cloudy, with the obscured sun
10 Partly cloudy, with brighter circumsolar region
11 White-blue sky with distinct solar corona
12 CIE Standard Clear Sky, low luminance turbidity
13 CIE Standard Clear Sky, polluted atmosphere
14 Cloudless turbid sky with broad solar corona
15 White-blue turbid sky with broad solar corona CIE standard sky types
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Skylight Distribution
The CIE standard helps with the distribution of daylight but it gives no information on the actual amount of daylight available at any particular time. There are a number of meteorological stations that record the global and diffuse (not including light direct from the sun) horizontal plane illuminance values on an unobstructed site and this data can be used to predict daylight availability. Whilst data is logged every five minutes or so at most measuring stations it is usually presented as a chart showing monthly averages of hourly values. The following chart shows typical data on daylight availability for the south of England, this will vary according to your location; BST corresponds to British Summer Time
BST
Time of day (BST) Time of day (GMT) Time anuar Fe ruar Marc April Ma une ul August Septem er Octo er No em er Decem er Time of year
The colour of the light from the sun and sky depends not only on the on the colour of the light from the sun but also on the way that light is absorbed and scattered by the atmosphere.
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Wave Length, nm
The above chart shows the standarised spectrum of daylight from CIE 15.2 which gives formulae for the calculation of daylight spectra of different colour temperatures. In practice, as the sky condition is constantly changing it is difficult to give exact values of the colour of the sky. However, the following table lists approximate values of correlated colour temperature for various sky conditions.
Sky condition CCT
Bright midday sun 5,200
Lightly overcast sky 6,000
Heavily overcast sky 6,500
Hazy sky 8,000
Deep blue clear sky 20,000
Light – achieving a balance
One of the skills of the lighting designer is achieving a balance between NATURAL light and ARTIFICIAL light. By capitalising on the natural light cast through windows, doors and skylights and then coupling this with a wide choice of artificial light sources within luminaires plus introducing occupancy/presence controls, daylight sensors and other technologies, the lighting designer can achieve a fantastic lighting scheme which also makes the most of natural light available and hence saves energy as well.
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Human Vision States
The eye consists of two key families of photo-receptors, which are sensitive to the wavelength and intensity of light. The entire surface of the retina is covered with Rod cells – so named because of their physical shape. Rod cells cannot distinguishcolour but are able to identify high and low brightness levels, and thus build up a picture of contrast of our external environment. This can be thought of as rather like a black and white photograph.
The centre of the retina, the fovea, is deficient in rod cells and instead populated by cone-shaped receptors. These are specifically present to introduce colour vision, and there are three types which are broadly receptive to red, green and blue wavelengths. Although we have limited colour vision beyond the centre of the retina, the brain remembers the colours of objects at the periphery of our vision and maintains a full colour image of our environment.
Photopic Vision The two different kinds of cells each function within specific light level ranges. At high illumination levels, cone cells predominate and the eye sees in full colour. This situation is termed “Photopic Vision”. Photopic vision is by far the most important to the lighting designer, because it determines our sight during daytime and virtually all indoor illuminated environments.
Scotopic Vision At very low lighting levels, e.g. starlight, there is no functionality of the cone cells. Only the rod cells are active and they build up a contrast image of our visual environment. No colour perception is possible and this state is called “Scotopic Vision”.Scotopic vision is less important and is rarely encountered. Even on a dark street there will be some degree of photopicvision.
Mesopic Vision At intermediate lighting levels the rod cells still predominate, but there remains partial functionality of the cone cells. Limitedcolour perception is possible in the brighter areas, and this condition is known as “Mesopic Vision”. It is a less well defined state existing between Photopic and Scotopic vision, whose precise nature is dependent on the actual illumination level.
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The rod and cone cells each function more efficiently under certain wavelengths of light – further job of the lamp engineer to develop sources that radiate as much light as possible near the areas of peak sensitivity, in order to produce the maximum light for the minimum consumption of electrical energy. Figure 9 illustrates the Photopic and Scotopic spectral response curves of the human eye superimposed over the SPD of a high pressure sodium lamp. Since this radiates much of its energy near the peak photopic sensitivity of the eye, it has a very high luminous efficacy.
Scotopic P otopic
Relative Spectral Power
Wave Length, nm
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LAMP HISTORY
As we sit here in the 21st Century, there are many different types of light source. The last 150 years has seen amazing developments in light. Everybody is talking about solid-state LED lighting being the future of lighting, but how did electric lighting originally come about? In the mid-late 19th Century, artificial light was provided by either Candle or Gas-lighting. Englishman Sir Joseph Swan and American Thomas Edison are both credited with developing the incandescent light bulb. In 1878 and 1879, respectively, they both managed to develop a light source which was affordable and suitable for domestic use. At the same time, Edmund Germer was conducting work on the mercury vapour fluorescent lamp.
However, it wasn’t until the 1940’s that the first practical and viable fluorescent lamp was launched; General Electric had bought the original patent and improved on the original design to make it suitable for the US market. From 1950 onwards, various new light sources were invented. The following graph shows the development and improvement in light output for given electrical light sources. Note that luminous efficiency is markedly different for different lamp types.
The LIA Light Source Guide has been compiled by the Low Pressure Sodium Lighting Industry Association to help users in the choice Hig Pressure Sodium of appropriate types of lamps for lighting commercial, Metal Halide Fluorescent institutional and industrial installations (special lamps, Hig Pressure Mercur such as for vehicle and photographic use have not Semiconductor been included). Tungston Halogen Incandescent The principal types of lamps are reviewed within the LIA Light Source Guide and their different characteristics are explained. It is important to understand the various lamp characteristics not only when dealing with new installations, but also when older installations are up-dated to an improved lighting standard or in order to save energy. Good lighting, using the latest lamps and luminaires, can pay for itself in reduced running costs as well as improving working conditions.
NB. The LIA Light Source Guide is only intended to help users make their initial decisions. Once more precise
Luminous Efficacy (lm/W) technical information is required (e.g. up-to-date values of light output) it is essential to consult the latest technical literature from LIA lamp manufacturers.
Year
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LAMPS
Methods of Producing Light
There are a number of different means of producing visible Light, The following list is not exhaustive but provides an insight into the 5 main forms of artificial light:-
Low High Tungsten Pressure Pressure Filament Sodium Mercury Induction Light Metal (Mercury, Emitting Hallide Low Sodium & Diode Pressure Compact Sulphur) High Mercury Tungsten Fluorescent Pressure (Fluorescent Tube Halogen Sodium Discharge LED tube) Induction Fluorescent Incandescent
There are ten principal families of lamps, according to their manner of light emission, which fall into the five main categories.
Incandescent
Incandescent lamps are a source of electric light that works by incandescence, (i.e. heat-driven light emissions). An electric current passes through a thin filament, heating it until it produces light. The enclosing glass bulb prevents the oxygen in air from reaching the hot filament, which otherwise would be destroyed rapidly by oxidation. Various gases are used to control premature burnout of the filament and in the case of halogen, prevent blackening of the glass.
• Conventional Incandescent • Halogen
Light Emitting Diodes (LEDs)
An LED lamp is a type of solid state lighting (SSL) that uses light-emitting diodes (LEDs) as the source of light, rather than electrical filaments, plasma (used in arc lamps such as fluorescent lamps) or gas.
LED lamps (also called LED bars or Illuminators) are usually clusters of LEDs in a suitable housing. They come in different shapes such as strips or on a PCB included in a Luminaire. There are also standard retrofit shapes available such as B22/E27 cap to retrofit Incandescent lamps or the MR16 retrofit Halogen lamps with a GU10 or GU5.3 bi-pin base.
• Light Emitting Diode (LED) • LED Modules • Organic Light Emitting Diode (OLED)
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Discharge
Gas-discharge lamps are a family of artificial light sources that generate light by sending an electrical discharge through an ionized gas. The character of the gas discharge critically depends on the frequency or modulation of the current. Typically, such lamps use an inert gas (argon, neon, krypton and xenon) or a mixture of these gases. Most lamps are filled with additional materials, like mercury, amalgam, sodium, and/or metal halides.
In operation the gas is ionized, and free electrons, accelerated by the electrical field in the tube, collide with gas and metal atoms. Some electrons circling around the gas and metal atoms are excited by these collisions, bringing them to a higher energy state. When the electron falls back to its original state, it emits a photon, resulting in visible light or ultraviolet radiation. Ultraviolet radiation is converted to visible light by a fluorescent coating on the inside of the lamp’s glass surface for some lamp types.
The fluorescent lamp is perhaps the best known gas-discharge lamp. Discharge lamps tend to fall into 2 categories:-
Low Pressure Discharge High Pressure Discharge
• Fluorescent • High Intensity Discharge (HID) • Compact Fluorescent (CFL) • Mercury Vapour • Low Pressure Sodium • Metal Halide • High Pressure Sodium • Xenon Arc Credit: Osram Ltd.
Induction
In contrast with all other electrical lamps that use electrical connections through the lamp envelope to transfer power to the lamp, in electrodeless lamps the power needed to generate light is transferred from the outside of the lamp envelope by means of (electro)magnetic fields.
There are two advantages of eliminating electrodes. The first is extended bulb life, because the electrodes are usually the limiting factor in bulb life. The second benefit is the ability to use light- generating substances that would react with metal electrodes in normal lamps.
Two systems are described below—one based on conventional fluorescent lamp phosphors and a second based on the use of radio waves energizing a bulb filled with sulphur or metal halides.
• Fluorescent Induction • Radio-generated plasma lamps
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Notes
1. Fluorescent lamps incorporate a low pressure Mercury discharge but the majority of the light output is from the fluorescence of the phosphors which coat the inside of the glass.
2. High pressure discharge lamps are sometimes known as High Intensity Discharge lamps (HID).
3. The Pressure of the High Pressure Sodium Lamps is less than one atmosphere, but they are so called to distinguish them from Low Pressure Sodium Lamps.
4. Many lamps require separate control gear, but some compact fluorescent and Induction lamps incorporate integral control gear.
GLS
Tungsten Halogen
W ite SON
HP Mercur
Compact Fluorescent
Induction Lamp IGD
Halop op ate Fluorescent Tu es
Metal Holide Light Source Trip osp or Fluorescent Tu es
LED
Efficacy Lm/W
Basis of lamp selection (based on bare light sources)
Lighting design guidance may be obtained from the various publications issued by the Society of Light and Lighting. Subject to their recommendations (illumination level, colour rendering, reduction of glare etc.) preference should be given to lamps with an efficacy as high as possible.
The chart (Fig.3 page 9) indicates the ranges of efficacies available for common lamps of each family. Nevertheless, the fact that there are so many lamp types indicates that they all have their applications.
Once lamps are installed in luminaires, the overall efficacy would be affected by 3 main factors:
• Control Gear • Thermal losses • Luminaire Design (e.g. as measured by Light Output Ratio (LOR))
For example, with an LED installed in a light fixture, the efficacy could reduce to 50% of its original (discrete) LED rating i.e. 50lm/w.
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INCANDESCENT
How it works Glass ul Gas Filling Incandescent Lamps are commonly referred to as ‘Light bulbs’. Light bulbs have a very simple structure. At the Tunsten base, they have two metal contacts, which connect to an Filament electrical circuit. The metal contacts are attached to two Support stiff wires, which are attached to a thin metal filament. The Wires filament sits in the middle of the bulb, held up by a glass Lead Wires mount. The wires and the filament are housed in a glass Dumet Wire bulb, which is filled with an inert gas, such as argon. E aust Tu e When the bulb is connected to a power supply, an electric Stem current flows from one contact to the other, through the Fuse wires and the filament. The filament is made of a long, incredibly thin length of tungsten metal. In a typical 60-watt Cap bulb, the tungsten filament is about 2 meters long but only 0.25mm thick. The tungsten is arranged in a double coil in order to fit it all in a small space. In a 60-watt bulb, the coil is less than 25mm long.
Type
As incandescent lamps have been in the market for over a century and originated as the main light source for domestic dwellings, many different types and sizes are available. See below. The most common shape would be the ‘GLS’ or ‘General Service Lamp’ which would typically be found in pendants, standard lamps or table lamps. The next most popular lamp is the ‘candle’ shape which as the name suggests, effectively replaced the candle wall fixtures of the 19th century.
However, there are many other types such as ‘Globe’, ‘Reflector’, ‘Tubular’ etc. Reflector lamps (either blown bulb or PAR) are similar to GLS lamps but have a bulb with an internal reflector coating. Replacements should normally be of the same type as originally used unless it is desired to change the beam intensity and width. Crown-silvered lamps are intended to be used in conjunction with a metal reflector as part of the luminaire.
With the pressure to reduce energy consumption, the last 5 years has seen the consumer shift across from purchasing incandescent lamps to their replacement, Compact Fluorescent Lamps.
Size
Incandescent lamps tend to be measured in terms of their power output or wattage. Over the years, the GLS lamp has reduced in size from 65mm diameter to 60mm to its current 50mm. Many of these shapes have a designation consisting of one or more letters followed by one or more numbers. The letters represent the shape of the bulb, numbers represent the maximum diameter, in millimeters e.g. A55 or in eights of an inch or PAR16 (i.e. 2”).
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Lamp Base
As Incandescent lamps have been in the market for over 150 years, there are numerous bases available to suit every application.
Efficacy
Incandescent lamps offer a low efficacy as the majority of energy consumed is converted into heat. A typical range would be 8-14 lm/w. The following table details the typical efficacies of the most common incandescent lamps.
Wattage
25 40 60 100
Efficiancy Energy Efficiancy Energy Efficiancy Energy Efficiancy Energy Lamp Type (lm/W) Rating (lm/W) Rating (lm/W) Rating (lm/W) Rating
GLS Clear / Frosted 9.2 E 10.4 E 11.8 E 13.4 E
GLS White 8.0 E 9.0 E 10.3 E 11.7 E
GLS Clear / Frosted - - 7.5 E 9.0 E 10.8 E 2500 hours Candles & Sphericals 8.4 E 10.0 E 11.0 E - - Clear / Frosted Candles & 7.2 E 9.0 E 10.0 E - - Sphericals White
Fireglow - - - - 3.3 E - -
Daylight - - 5.0 E 5.0 E - -
Energy Rating
Even though they produce a high quality light, Incandescent lamps are the least efficient light sources. Typical energy ratings for incandescent lamps would be ‘E’ i.e. not very efficient. Under the ErP Directive, between 2009 and 2018, the majority of traditional incandescent lamps for general lighting purposes will cease to be sold in the UK.
Life
The life of an incandescent lamp will typically be between 400 and 2,000 hours, dependent on the quality of the components used. End of life would be determined by the life of the filament. Failure can often be due to shock or vibration, which the lamp has sustained during transit, installation or use.
Also, during usage, the filament evaporates forming a black coating on the inside of the glass until eventually the filament thins and breaks. Some suppliers offer extended life GLS lamps e.g. 16 times normal life is claimed. These lamps are approximately half the efficacy of standard-life GLS lamps, which means they give only half the light output for the same power consumption.
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Run-Up
Incandscent lamps start up almost instantly and achieve full brightness within less than one second.
Dimming
One of the advantages of incandescent lamps is that they can be dimmed, utilising a standard Analogue (rotary) or DorS (digital) dimmer.
Voltage
Incandescent lamps commonly operate directly on mains voltage, 220v – 250v AC, although many other voltages are offered. Incandescent lamps are very sensitive to changes in voltage.
For example, a supply voltage 5% higher than normal reduces lamp life by 60% but increases light output by 20%, whereas a supply voltage 5% lower would increase lamp life by 100% but reduce light output by 20%.
Lumens, Amps
Percentage Life Percentage
Watts, Percentage
Lumens, Amps Percentage Life Percentage Percentage Watts, Watts, Percentage
The graph shows the effect of changes in the supply voltage on GLS filament and tungsten halogen lamps. For exampe, a supply voltage 5% higher than nominal reduces lamp life by 60%.
Colour Temperature
A typical incandescent lamp would produce a colour in the range 2,500 – 2,700 Kelvin. Incandescent lamps are recognized as producing a cosy, warm white light.
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Colour Rendering
An incandescent lamp offers high colour rendering (100 on the CRI scale) i.e. it helps objects and persons illuminated to appear truer to life.
Finish
There are many different variations of finish available. Standard Incandescent finishes would be:-
• Clear • Pearl • Pastel Colours
Consumers would tend to choose a particular finish to suit the application within their dwelling i.e. with an open shade, a ‘pearl’ finish would provide less glare than a ‘clear’ type.
Application
Filament lamps are mainly used for domestic and display lighting.
Advantages
Low cost, simple operation, good colour rendering, dimmable.
Disadvantages
Low efficacy and relatively short life.
Example of Range
The following table denotes the wide choice of shapes, sizes and colours in incandescent.
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Key Properties
Operating Position Any
Control Gear No
Starting Instant
Restarting Instant
Colour Temperature (K) 2500-2700
Colour Rendering (CRI) 100
Efficacy lm/W 6-16
Dimmable Yes
Cost Very Low
Standards
• BS EN 60432-1: Safety specification for incandescent lamps. Tungsten filament lamps for domestic and similar general lighting purposes. • BS EN 60064: Tungsten filament lamps for domestic and similar general lighting purposes - Performance requirements • BS EN 50285: Energy efficiency of electric lamps for household use – Measurement Methods • BS EN 60630: Maximum lamp outlines for incandescent lamps
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Halogen Lamps
A halogen lamp is an incandescent lamp in which a tungsten filament is sealed into a compact transparent envelope filled with an inert gas, plus a small amount of halogen such as iodine orbromine. The halogen cycle increases the lifetime of the bulb and prevents its darkening by re-depositing tungsten from the inside of the bulb back onto the filament.
The halogen lamp can operate its filament at a higher temperature than a standard gas filled lamp of similar power without loss of operating life. This gives it a higher efficacy (10-25 lm/W). It also gives light of a higher colour temperature compared to a non-halogen incandescent lamp.
Alternatively, it may be designed to have perhaps twice the life with the same or slightly higher efficacy. Because of their smaller size, halogen lamps can advantageously be used with optical systems that are more efficient.
Dissociation of Tungsten Halogen Tungsten Tungsten Halogen Compound Compound
Type
Tungsten Halogen lamps have an increased light output and/or extended life compared with standard filament lamps. The bulb is of small dimensions, and made from quartz or hard glass. The most common halogen lamps tend to fall into 2 groups:-
Reflectors Non-Directional
GU5.3 MR16 Low Voltage (12V) G4 GU4 MR11 GU10 G9 PAR16 SES Candle BC/ES/SES PAR20 Mains Voltage (230V) GLS BC/ES/SES PAR25 ES PAR30 ES Linear R7 R50 SES/ES
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Halogen lamps are available in a very broad range. No one will forget the mains voltage R7 halogen lamps for exterior floodlights.
Voltage
One of the toughest decisions for the user to decide is which voltage. Original Halogen lamps were available in Low Voltage (12V) for use with a transformer to convert mains voltage into low voltage. 15 years ago, the GU10 Mains Voltage Halogen lamps were invented, negating the need for a transformer, thereby reducing cost, simplifying installation and maintenance.
Reflector
A reflector allows the user to direct light onto a particular surface or light an area or object. Typical beam angles would be 24 degrees or 38 degrees. A halogen lamp with a narrow beam angle is referred to as a ‘spot’ and a wide angle as a ‘flood’.
Dichroic or Aluminium Reflector
As well as producing excellent light output, a tungsten halogen lamp also produces a significant amount of heat. A dichroicreflector sends the majority of the heat backwards into the ceiling void or recess which is ideal for a ‘spot’ in an enclosed space. An aluminium reflector send the majority of the heat forwards which is ideal for enclosed light fittings, such as fire rated down-lights where the luminaire is completely enclosed.
Wattages
The most common wattage is 50W. However, lower wattages are now being specified due to the need to reduce energy consumption. Some ‘Energy Saving’ halogen lamps can offer the equivalent light output matched with 20-30% energy saving.
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Energy Savers
• The technology used to achieve ‘Energy Saving’ versions depends on the voltage:- • Main Voltage Halogen lamps utilize a special gas fill to achieve a higher efficacy • Low Voltage Halogen lamps utilize an special Coating on the capsule which converts heat into visible light, hence Infra Red Coating (IRC)
Energy saving Halogen lamps are now available in the following types:- • Low Voltage Reflector and Capsule lamps • Mains Voltage Reflector (e.g. MR16) and Capsule lamps • GLS & Candle Look-a-Like Lamps to replace traditional incandescent lamps • Mains Voltage Linear Halogen lamps
Cap Type
Many different cap types exist.
UV
High temperature filaments emit some energy in the UV region. Small amounts of other elements can be mixed into the quartz capsule, so that the doped quartz (or selective optical coating) blocks harmful UV radiation.
Efficacy
The efficacy depends on the voltage and whether or not it is an energy saving version:
Dimming
One of the main reasons for the use of halogens has been the ability to dim them. With legislation demanding more efficient lamps, halogen is being challenged by other light sources such as CFL and LED. However, with the advent of Energy Saving versions, halogen once more offers a good all round package with its excellent colour rendering, bright light, improved efficacy coupled with dimmable capability.
Run-Up
Incandescent lamps start up instantly and achieve full brightness within less than one second.
Colour Rendering
An incandescent lamp offers high colour rendering (100 on the CRI scale) i.e. it helps objects and persons illuminated to appear truer to life.
Colour Temperature
A typical halogen lamp would produce a colour in the range 2,700 – 3,200 Kelvin i.e. a relatively comfortable, warm white light.
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Transformers
Low Voltage halogen lamps require a transformer to convert mains voltage into low voltage. Historically, halogen lamps have been linked up - perhaps 2-4 lamps per transformer. However, it is good practice to install 1 lamp to 1 transformer.
Application
Halogen lamps are ideal for installation in the home, retail environments, studio in fact anywhere a bright, warm instant light is required.
Advantages
Low cost, simple operation, excellent colour rendering, sparkle/bright light, dimmable. ‘Energy Saver’ halogen lamps meet the Energy Class ‘B’ or ‘C’ under the requirements of ErP Directive. Longer life verses standard incandescent.
Disadvantages
Lower efficacy and relatively short life, compared to other lamps such as fluorescent or LED.
Example of Range
The following table denotes the wide choice of shapes, sizes and colours in halogen.
Double Ended Single Ended Single Ended Single Ended Double Jacket Mains Volt Low Volt Low Volt IRC Mains Volt Halogen
MR16 AR111 GU10 PAR Halogen Blown Glass Low Volt Low Volt Mains Volt Mains Volt Mains Volt
Standards
• BS EN 60432-2: Incandescent lamps. Safety specifications. Tungsten halogen lamps for domestic and similar general lighting purposes • BS EN 60432-3: Incandescent lamps. Safety specifications. Tungsten halogen lamps (non-vehicle) • BS EN 60357: Tungsten halogen lamps (non-vehicle) - Performance specifications • BS EN 50285: Energy efficiency of electric lamps for household use – Measurement Methods
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LIGHT EMITTING DIODES (LEDS)
Light emitting diodes (LEDs) are a recent lighting technology that is sometimes referred to as solid state lighting (SSL). It is a rapidly developing and advancing technology with significant changes in performance occurring almost monthly. LEDs have also introduced a whole new vocabulary to lighting that is more aligned with the world of electronics; this guide seeks to define some of these as well as provide the reader with a basic knowledge of solid state lighting. How it works
A Light Emitting Diode (LED) is a semiconductor device that emits light when an electric current is applied in its forward direction.
An ordinary diode is one of the basic components that have been used in electronic circuits for over 100 years. A diode allows an electric current to pass in one direction only; in effect a sort of one way valve. Diodes are key components in circuits used to rectify alternating currents (ac) to direct currents (dc). Their size varies according to the voltage and current values involved.
In a LED, when the correct forward current is applied to it, a form of electroluminescence occurs whereby incoherent and narrow-spectrum light is emitted from the p-n junction in the solid state material. In effect, electricity is passed through a chemical compound (crystal) that is excited and generates light. The chosen compounds can alter the wavelength (and hence the colour) of the light emitted. The first LED to emit visible light was demonstrated in 1962 and its colour was red.
Current flow
p-type n-type
Holes Electrons p-n junction Emitted light
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How are LEDs made?
The basis, or heart, of a LED is a very small die, or chip, that is made by depositing semi-conducting materials onto a substrate, generally known as a wafer. A wafer is a disc that may be 100mm or 150mm in diameter and each will produce a large number of individual LED chips. This is an established, proven manufacturing process producing most of the world’s semi-conductors, integrated circuits and similar electronic components.
After testing and selection, for colour and intensity, each chip is assembled into a package that makes it a practical component to be incorporated into a circuit and used to make light. Packages vary in construction and size depending on the intended application and choice of materials.
Lens
Anode (+) Cathode (-) Anode (+) Cathode (-) Cathode Lead LED Chip
LED Diode
Anode (+) Cathode (-) Anode (+) Cathode (-) Thermal Heatsink
Outer Package Bond Wire
LED Diode
Light produced by LEDs
The light produced by LED chips can, in effect, cover the whole visible light spectrum plus infra-red and ultra violet. The emitted colour is determined by the choice of semi-conductor materials and each chip emits light in a comparatively narrow spectrum.
Typical LED Characteristics
Semiconductor Wavelength Colour V @ 20mA Material F GaAs 850-940nm Infra-Red 1.2v GaAsP 630-660nm Red 1.8v GaAsP 605-620nm Amber 2.0v GaAsP:N 585-595nm Yellow 2.2v AIGaP 550-570nm Green 3.5v SiC 430-505nm Blue 3.6v GainN 450nm White 4.0v
White light, however, is produced generally by either using a blue LED to shine through a yellow phosphor, or a number of coloured LEDs (comprising at least red, green and blue (RGB)) are combined to provide this broad spectrum light. The former method is used where only white light is required, while the latter offers the opportunity to vary the colour produced by managing the output of the component colours.
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Heat produced by LEDs
LEDs dissipate their input energy in both luminous flux and heat. The heat is generated at the P-N junction of the device and the temperature here is critical to the performance of the LED.
Tj – The Junction Temperature The junction temperature of a LED is an important operating parameter that must be maintained at an optimum value. Variations in the Tj can alter the efficacy, output spectrum and life of the LED. The characteristics of an individual LED chip are defined at a set value of the Tj, which is usually tested momentarily at 25°C as it comes from the production process. This is, however, not a real world measurement because most LEDs will be operating at much higher temperatures once they are incorporated into a luminaire.
Efficacy
The performance of LEDs is in constant development and their efficacy is improving all the time. LED suppliers highlight their progress with regular press releases claiming the latest ‘on the bench’ R&D lumens per Watt they have achieved. In the first quarter of 2013 one supplier claimed to have exceeded 250 lm/W, for a white light LED operating ‘on the bench’. However, these claims should not be confused with the real world performance to be expected from production LED chips. Typically, warm white (2700K – 3000K) LED chips are achieving around 150 lm/W and more, with improvements occurring almost continuously.
Commercial Cool Commercial Warm
Efficacy (lm/W) La Cool Commercial Warm not uali ied Commercial Cool not uali ied La not uali ied Fit La Fit Warm Fit Cool (all data)
Year
Once a chip has been incorporated in a LED luminaire the overall system efficacy will be reduced by the inclusion of the power consumed by the control gear (sometimes called a ‘driver’), as well as any light absorbed by the optics. Further loss of efficacy will occur if the luminaire forces the LED chip to operate outside its optimum operating parameters, especially with regard to its junction temperature (Tj). Nevertheless, some highly efficient control gears, optics and heat management solutions mean that some general lighting LED luminaires have already achieved in excess of 150 lm/W system efficacy.
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Life
The life of any light source can be measured in two ways; it’s actual survival or to that point when the light output has fallen below a useful level. Conventional lamp life is expressed as the time taken for 50% of the lamps to have failed. This is done because most lamps do not decline in output significantly during their rated life. This is not true for a LED source.
LED life – actual and useful
An LED light source operating in ideal conditions has a very long life when compared to most previous lamp technologies. Typically, manufacturers are claiming a life of 50,000 hours plus, with some even predicting as much as 100,000 hours. Because LEDs offer such extreme life, one of the biggest challenges is how to achieve actual performance over life measurements i.e. ‘real life’ data. Testing LEDs for 24 hours a day, 365 days per year, would only provide 8,760 hours of data. So LEDs rated at 100,000 hours would require 11.5 years to produce ‘real life’ data. The current pace of technological development, and the need to commercialise LEDs, makes this approach impractical and unworkable.
Some manufacturers use a 6:1 ratio to ensure data can be gathered and extrapolated. So, 1,000 hours actual testing would provide the data for up to 6,000 hours and 2,000 hours actual for the 12,000 hours prediction. The life of a solid state device like a LED also needs to be expressed in a different way compared with conventional lamp lifetimes. The life of individual electronic components usually conforms to a ‘bathtub’ mortality curve; a few die in infancy whilst the vast majority operate for their rated life and then failures accelerate thereafter.
The Bathtub Curve H pot etical Faliure Rate ersus Time
In ant Mortalit End o Li e Wear Out Decreasing Faliure Rate Increasing Faliure Rate
Normal Li e (Use ul Li e) Low Constant Faliure Rate Increased Faliure Rate Increased Faliure
Time
In the case of a LED the light output is known to reduce over life, so this light source does have some common ground with previous lamp types. However, the light output does decline to such an extent that it will not be useful, even though the LED will continue to operate. Depending on the application, the life of the device can be expressed as the time it takes to fall to a specific percentage of its original output.
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Lumen Maintenance – and maintenance factors
Historically, a conventional lamp’s life has been based on its mortality curve, which refers to the percentage of the lamps that fail over time. The most common mortality rating for these lamps is based on the time at which 50 per cent of lamps will have failed - see graph.
Non-preheat start Preheat start
Installed lamp luminous flux (%) Operating time (hours)
Most conventional lamps retain useful light output well beyond their rated life, which is not true for LEDs. They experience a gradual reduction in light output during operation and generally do not fail catastrophically. As a result the lighting industry has sought to develop alternative methods of defining the life of LEDs. The lifespan, and light output, of a LED depends on its operational and environmental temperature as well as the quality of its power supply. These factors also determine the rate of degradation of the light output. It is therefore possible to define the useful life of a LED by stating how long it will take to reach a certain percentage of its original light output. However, the individual LEDs will arrive at this point after different elapsed times. The industry is working on providing a standard measure for LED life and the draft of IEC62717 suggests two life parameters; a Median Useful Life (Lx) and an Abrupt Failure Value (AFV).
The Median Useful Life (MUL) is the time for 50% of a batch of products to fade to x% of its original light output, and the AFV is the percentage of LED light sources, or luminaires, of the same type that no longer provide any light at the MUL. This might be expressed as L70 = 50,000 AFV = 6%. These are comparatively recent life definitions and all manufacturers may not have adopted them yet; it is important, therefore, to make sure that the life they do quote is fully explained.
Further reading on LED life can be found in the LIA document TS01 and the IES publications TM21, LM79 and LM80.
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LED packages
A LED package may comprise just one chip or many and as a result there are many sizes, shapes and configurations available to the manufacturer of luminaires.
Beam Angle (Optics)
The package also provides protection for the semi-conductor crystal and also dictates the directionality of the light output. Usually this is constructed so that the light radiates in a near hemi-sphere of almost 180 degrees (the current maximum is about 160 degrees). Guidance of the light is thus easier than in filament or discharge lamps, which generally radiate light in all directions. There are various types of housings for LEDs of low, medium and high performance; whatever the choice, they should all give good mechanical stability.
The LED package may incorporate an optical component that helps to control the light output from the chip, whilst also offering mechanical protection.
LED modules
A LED package needs to be supported by additional components in order to manage its power and heat dissipation requirements. A number of LED packages may need to be brought together to form a single LED module, which is sometimes referred to as a LED light engine although this term is not used in International Standards (IEC).
The other essential component within a LED module is the provision of a suitable connection to its supply. This may also provide good thermal conduction to allow the generated heat to be taken away from the chip. This adds to the challenge of module construction, particularly with regard to heat density and the management the Tj of several chips.
Creating more diffuse light
The initial focus of LED development was based on the fact that the chips provided a very small, very intense light. This light source was suited to the creation of directional luminaires because an almost point source of light may be controlled very accurately. As the technology has developed it has become possible to increase the size of the light source by using many chips over a wider area. Delivering a more diffuse light from multi chip solutions has been done by using novel optics and the phenomenon of internal reflection as well as refraction.
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White LEDs
The majority of White LEDs used in general lighting applications are those using the combination of blue LEDs and phosphor coatings. This section looks at these types and considers their colour rendering properties, correlated colour temperature as well as the way they are constructed.
Using phosphors to produce white light
For many years phosphors have been used to make white light fluorescent lamps. Over time these phosphors have become more complex as ever better colour rendering has been sought; co- incidentally the lamps have also become more efficient. Using phosphors to produce white light is therefore well known to the lighting industry. The major challenge, in general lighting use, is to produce a broad spectrum of light that does not over visibly emphasise any one particular colour.
Watts per 5nm lm Watts nm
With LEDs the use of phosphors is simplified because the original light source is visible blue light so the addition of a carefully chosen yellow phosphor will produce white light. It is for this reason that most white light LEDs appear to be yellow when switched OFF.
Spectral Power Distribution
.
.
. Reletive Intensity
.
Wavelength (nm)
The combination of blue LEDs with suitable yellow phosphors can be done in different ways; the phosphor can be deposited directly onto the LED chip or onto a separate remote plate.
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Phosphor coated dies
A phosphor coating can be deposited directly onto a blue LED die to produce white light. The quality of the consequent white light emitted depends on:
• The quality of the phosphor • The consistency of the coating • The thickness of the coating
These factors also influence efficacy, which is why cool white LEDs are more efficient than warm white ones. The latter have a thicker layer of phosphor which reduces the light output.
Remote phosphor LEDs
An alternative approach uses a number of blue LEDs (sometimes known as ‘pumps’) to shine through a remote plate coated in an appropriate phosphor. This approach produces a lower glare light source when compared with individual LEDs. Additional benefits include better colour consistency over life and improved efficacy. The preferred LED colour choice for these applications is often referred to as Royal Blue.
Blue LEDs
Mixing Chamber Remote Phosphor
The construction of a remote phosphor device comprises an array of LEDs enclosed within a mixing chamber that passes its light through the coated plate or substrate. These assemblies are often produced as LED modules which also may be designed to conform to an agreed standard physical package that allows the future replacement of this element within a LED luminaire.
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Colour rendering of White LEDs
White LED light can be created by using either phosphor coated dies or a red, green, blue (RGB) combination. The latter may even be supplemented by a fourth colour, usually yellow or amber. The spectral power distributions of these two methods are very different, which means that the use of a calculated (measured) CRI ranking may not match a visual ranking. The current CRI calculation method was introduced in 1974 but there have been several research papers that have questioned it suitability for all types of light sources.
A recent review by the CIE (Commission Internationale d’Eclairage) Technical Committee (Ref: CIE 177:2007) concluded that a supplementary method is required to better describe the performance of white LEDs. In the meantime it is worth noting that there are warm white LED sources with CRIs up to Ra98. Almost all white LEDs designed for general illumination are now exceeding Ra80. While the development of new metrics is being considered it is recommended that white LEDs are also subjected to visual assessments in the intended application if there is any doubt about the claimed CRI.
Colour consistency
Due to very small variations in manufacturing conditions individual LEDs will have different CRIs. The chips are therefore tested and selected, or binned, for colour consistency across a range of values. This permits customers to choose their LEDs for consistency of appearance and quality. Bins might be defined by one or two Macadam ellipses for high quality, professional applications; 3 - 4 ellipses for commercial use and even wider values where the consistency is less critical. See also EU Directive 1194/2012.
Correlated colour temperature (CCT)
White LEDs can be supplied in a range of CCT values. Early white LEDs were often offered in a cool white with a CCT in the order of 5000K; this was largely driven by the fact that such LEDs were more efficient because less phosphor was required. It is still the case that a cool white LED is more efficient than a warm white version.
Note on spectral power distribution (SPD) graphs: Most SPD graphs reproduced in colour show both the wavelength and a representation of the visual colour spectrum. Always check that the stated wavelength values correctly match the colour above them. In particular 550nm should be aligned with a nice bright green. Credit: Osram Ltd.
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Coloured LEDs
Figure 3 has already shown that LEDs are available in a wide range of colours. These can be combined to extend the hues available to the lighting designer. Coloured LEDs can also be combined with white LEDs to alter the CCT, or to produce special effects related to the expected colour appearance when (e.g.) dimming a luminaire.
Coloured LEDs have a range of efficacies according to their colour but are much more efficient than using coloured filters with conventional white light sources.
Luminous efficacy Lumen/watt Red Green Blue White
Chip target (USDOE) 186 270 69 243
Chip current - direct from die @ 25C Tj 168 217 62 131
Sold package best 79 112 45 104
Sold package worst 16 17 6 25
Coloured LEDs are used in architectural lighting schemes and applications where particular wavelengths of light are beneficial. They are increasingly used in signalling applications including traffic lights.
Photobiology
Light plays a very important role in our wellbeing and health but it can also be harmful if used incorrectly. Sunshine is good for us but if we expose ourselves to it for too long it can cause sunburn as well as more lasting harm to our skin. The same balance needs to be maintained when we are dealing with artificial light. In LEDs the current concerns relate to the use of blue light, which effectively covers most of the white sources available.
Blue light
The invention of the blue LED was the key to creating white light by using phosphors. This does mean that there can be a ‘blue’ peak in a white LED spectrum and it is therefore worth taking this into account for certain minority health groups. On balance blue light is more generally beneficial and it should always be remembered that it is present in sunlight. Lighting LEDs do not, however, produce heat on the skin, i.e. there is no forward infra-red radiation.
A risk assessment of the blue light component of a white LED is, therefore, only necessary where there are likely to be subjects / patients with a known sensitivity condition, or the type of light involves illuminating a part of the body from a distance less than 20cm for several hours at a time. In the latter case it might involve an illuminated inspection lamp and the risk might be mitigated by selecting LEDs with reduced power in the blue area of the spectrum.
It is very important to note that these effects are limited to a very small number of people. The EU Directive 2006/25/EC addresses the issue of risks arising from optical radiation and the Non-binding guide to good practice for implementing Directive 2006/25/EC provides much useful additional reading. Much of this work covers the use of lasers, which should not be confused with LED lighting. Useful further reading on this subject can be found by following these links: (Link: Human Centric Lighting: Beyond Energy Efficiency – LightingEurope, July 2013; and Photobiological Safety in Lighting Products for use in Working Places – LightingEurope, February 2013)
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Powering LEDs
The LED itself is an electronic component, which will require a power supply to provide the correct voltage and current to suit its characteristics. The vast majority of LED chips and packages are very low voltage dc devices, although there are some that can be connected directly to the ac mains. The voltage and current required will determine the type of power supply, as will the need to control the light output. The performance and quality of an LED’s power supply will have a critical effect on its life, efficacy and light output.
Power supplies for LEDs are called ‘control gear’ (sometimes referred to as ‘drivers’) and these perform a similar function to their namesakes used with fluorescent and other discharge lighting sources. This equipment can be designed to power anything from a single LED to many hundreds. It is important to control the forward current to ensure the optimum performance is obtained.
Lumens
Current (mA) Many current LEDs are being over-driven to maximise the lumen output rather than achieve their best efficacy. In effect the potential ‘lumens per Watt’ performance is compromised in favour of producing more lumens from a LED. It is for this reason that dimming some LEDs may increase their efficacy at certain lower outputs. (See ‘Controlling LEDs.)
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Technical issues
Orientation – LEDs can be used in any orientation because they are solid state devices, have no moving parts and are not filled with gasses.
Run-up time – A LED will turn ON instantly at full brightness, or even at a pre-determined dimmed level. There is no significant, visible, warm-up period and no need to start at 100% output prior to dimming.
Re-strike time – There are no restrictions on either a ‘hot’ or ‘cold’ re-strike for a LED; it may be turned ON at any time and will produce instant light.
Supply voltage – The vast majority of LEDs operate at extra low voltage and require a direct current supply. As a result any fluctuations in the 230V ac mains supply will only affect the control gear powering the LED. Well designed control gear will isolate the LED from any such mains fluctuations and protect it from spikes and other disturbances.
Managing heat in LEDs
Maintaining a reasonable junction temperature in an LED is important for reasons of performance and life. Heat must be extracted from the LED as quickly and efficiently as possible so that the Tj does not exceed its design level. This means that there must be a very good thermal path from the LED to the luminaire and out to the surrounding air. It is for this reason that most LED luminaires have obvious heatsinks, as well as clear advice about their location and local ambient temperature requirements.
In circumstances where it is not possible to optimise the heatsink (e.g. in some replacement lamp solutions, or when using replaceable LED modules) the stated life may be lower.
Controlling LEDs
LEDs are very well suited to being controlled because they can be turned ON instantly, and their output can be varied readily from 0% - 100% with the correct control gear circuits. Neither the switching cycle nor the dimming process has any impact on an LED’s life; further demonstrating their suitability for being controlled. However, dimming and switching may affect the life of control gear, depending on its design and components.
Dimming
The available techniques for dimming LEDs are determined by whether it is a LED lamp (i.e. an integrated LED and control gear intended to replace an existing conventional 230V lamp) or a LED luminaire. A LED lamp is only connected to the mains supply and can only be dimmed by altering that supply using either phase-cut or sine wave dimming. On the other hand a LED luminaire, which will have an associated control gear, can be dimmed electronically; either by constant current reduction or pulse width modulation (PWM).
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Controlling LED Lamps
When existing, conventional, 230V ac lamps (e.g. incandescent GLS or tungsten halogen spots) are replaced by LED lamps and use the existing lamp holders, control options may be limited. Switching ON and OFF will always be possible but dimming may not be. The compatibility (or otherwise) between a phase cut dimmer and the LED lamps is dependent on a number factors. Many dimmers rely on the load to be above a minimum value, which is often higher than the total load presented by the new LED lamps. Other compatibility issues relate to whether the dimmer is a trailing or leading edge design, which might be a legacy of the original load being either magnetic or electronic.
Before carrying out a major LED lamp replacement programme it is well worth while carrying out tests to see if the LEDs are compatible with the existing controls. Incompatibility can be shown by the LEDs flickering, the dimming range being limited or even the generation of audible noise.
Controlling LED luminaires
Although it is possible that a new LED luminaire might be used to replace a luminaire that is already controlled by a dimmer it is more likely that it will be installed with appropriate new controls. A new LED luminaire will be supplied with control gear, which will be either ‘switching only’ or fully dimmable. If it is the latter then the dimming control commands may be analogue or digital; full information will be provided on the control gear.
Dimming control commands
A dimming control gear may be controlled by 1-10V dc, DALI, DSI or DMX signals; indeed some may offer the option of all three. There are also control gears that can be directly connected to a local area network (LAN) and able to respond to TCP/IP instructions. This will be the case when using ‘Power over Ethernet’ systems or wi-fi based controls. Whatever the command protocol used, the control gear will usually offer a full dimming response from 0% - 100%.
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Dimming operation
The light output from a LED is a function of the forward current passing through the device. It is therefore possible to dim a LED by reducing the forward current. However, many LEDs will experience significant colour shift at lower forward current levels. The forward current level also affects the Tj and the efficacy of the device. This is the analogue approach to dimming LEDs.
An alternative approach to reducing the apparent light output is to use pulse width modulation (PWM), where the LED is – in effect – turned ON and OFF very rapidly. The duty cycle (ON period) then dictates the apparent brightness of the LED.
.
25% dimming. LED(s) are “on” 75% of the time. .
.
. 50% dimming. LED(s) are “on” 50% of the time. . Relative Light Output .
75% dimming. LED(s) are “on” 25% of the time. Forward Current (mA)
Pulse width Modulation (PWM) dimming Analogue dimming via reduce forward curent
In order to avoid any possible flicker problems – either visible or invisible – the frequency of the PWM used must exceed 3000Hz. The benefit of using PWM is that the colour appearance of the LED is constant and the dimming curve is virtually linear.
If colour consistency is important in a given application then the supplier of the LED fixture should be consulted about the most appropriate control method.
Additional comment re flicker
Another source of flicker is the 50Hz mains frequency, which may not be entirely eliminated by the LED’s control gear. If the sinusoidal ripple is not sufficiently damped then it is possible for strobe effects to occur and/or perceptible flicker. Partial damping may still give rise to an imperceptible flicker that is still registered by the brain.
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Advantages
LED lighting is proving to be a highly versatile and very efficient new light source. It offers the benefits of:
• A very long service life • Instant start and re-start • Physically robust and largely shock proof • Reduced environmental impact ; both in manufacture and use • Wide choice of colours • Good colour rendering from high quality white LEDs • Highly controllable; switching cycles have little or no impact on device life • Very compact sources allowing highly efficient optics and less wasted light (spill) • No forward UV or IR possible, unless specifically required.
Initially offered as single dies (or chips) providing an almost point source of light, the LED has rapidly evolved from a device thought to be only appropriate to directional and effect (coloured) lighting. LEDs are now available in a wide range of form factors and are challenging virtually all the lighting applications covered by other lamp technologies. The only barrier to wider adoption is the higher original cost of most LED luminaires when compared to established solutions, but even this is diminishing owing to recent price reductions.
Disadvantages
Aside from the question of cost there are very few real disadvantages in using LED sources. There are stories of LED traffic lights generating insufficient heat to clear away obscuring snow but this can be overcome by design. The intensity of an individual high power LED can be uncomfortable but proper optical design and glare control can be applied. Their use in high ambient operating temperatures can be a problem and here more conventional light source may hold their own for longer.
Standards and other relevant publications
There are a number of standards and other publications that are relevant to the production, specification and use of LEDs. Many of these are those that have been applied to conventional lighting products but there are several that have been developed specifically for LEDs.
Current standards and guidance – Please refer to LIA Information Sheet 14, which is kept up to date.
WEEE and RoHS – LEDs are electronic components and are subject to legislation regarding the use of hazardous substances in manufacture as well as disposal at the end of life.
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FLUORESCENT LAMPS
Tubular Fluorescent Lamps
A tubular fluorescent lamp consists of a cylindrical glass tube, coated on the inside with fluorescent phosphors. Each fluorescent tube contains a minute dose of either mercury or amalgam and a mixture of inert gases, such as argon and krypton or neon and argon. At either end of the tube are electrodes (cathodes) which pass an electrical charge from one end to the other, exciting ions in the process.
As these ions pass down the tube, they collide with particles of mercury and produce ultraviolet radiation. This in turn radiates onto the phosphor coating which produces visible white light. Colour temperature and colour rendering can be determined by the phosphor mix coating on the inside of the tube.
Aluminium Cap Electrode Coil Argon r pton Atoms Glass Tu e
Glass Stem Cat ode S ield Li uid Mercur P osp or Coating
Size
In the UK, the diameter of Tubular Fluorescent Lamps is identified by using the ‘T’ prefix and then a number which is a fraction of an inch. Historically, T12 and T8 lamps have been utilized which are 12/8ths and 8/8ths of an inch in diameter, which would equate to 38mm and 25mm respectively.
Over the years, in new installations or major refurbishments the trend has been to utilise a narrower diameter tube T5 (16mm). T5 fluorescent lamps offer higher efficacy and reduced luminaire size. EU legislation is driving the replacement of T8 and T12 by T5.
T5 Slimline T8 Krypton T12 Argon Circline / U
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Phosphor Coating
Lamps with the traditional Halophosphor coating are now being rapidly superseded by lamps with the more efficient Triphosphor (Multi-phosphor) coating. Whereas Halophosphor lamps can only be used with conventional switch-start, electro-magnetic, control gear, Triphosphor lamps can be used for both switch-start and high frequency, electronic, circuits.
Triphosphor lamps are more energy efficient; improving the light output of many luminaires and offer long term cost savings. In addition they provide better colour rendering, improved lumen maintenance and longer life. Multi-phosphor coated lamps are also available which offer high efficacy and excellent colour rendering.
Halophosphor
Halophosphor is a blend of two different materials which radiate broadly in the blue and orange parts of the spectrum. By changing the ratio of the two components a full range of warm to cool white hues can be achieved.
Some typical spectral power distributions for the Warm, Cool and Daylight White Halophosphate lamps are illustrated below.
The colour rendering index is typically 50 to 70 and the lamp efficacy approx. 60 – 75 lm/W.
Triphosphor (Triband or Multi-Phosphor)
The following three fluorescent components are generally employed in modern triphosphor tubes:
• Barium Aluminate (BAM) Blue 450nm • Calcium Tungstate (CAT) Green 543nm • Yttrium Oxide (YOX) Orange-Red 611nm
These 3 bands correspond closely to the red, green and blue photo-receptors in the eye. By blending together the blue, green and red components in the correct proportions, a net white output of various hues can be realised. The distinctive triple-peak spectra of the triphosphor colours is illustrated below for three popular shades of white. Note that the cooler the colour temperature, the greater the proportion of blue light in the spectrum.
Owing to the proximity of these peaks to the colour receptors in the human eye, a very high colour rendering index is achieved. Typically this is of the order of Ra85 for most products, which marks a considerable improvement over Halophosphate materials.
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CRI Wheel - 4000k Halophospher CRI Wheel - 4000k Triphospher
Ra Ra R14 R1 R14 R1
R13 R2 R13 R2
R12 R3 R12 R3
R11 R4 R11 R4
R10 R5 R10 R5
R9 R6 R9 R6 R8 R7 R8 R7
An advantage of these deeply saturated coloured phosphors is their efficiency in converting UV into visible light. As a result lamp efficacy is typically around 80 – 95 lm/W. Under the ErP Directive, less efficient Halophosphor lamps will be replaced by Triphosphor lamps.
The following table illustrates how payback can be achieved in approx 1 year (correct as at 2015). F T Halop osp or F T Trip osp or
Total Cost of Ownership ( € ) Total Age of Installation (Years) Colour
Two factors concerning colour need to be considered when selecting fluorescent lamps:
• colour rendering, and • colour appearance (or temperature)
Colour Rendering
As we all know natural daylight is not a single colour, but a whole range – as seen in a rainbow. It is this colour spectrum that allows our eyes to see in a way that we perceive to be natural and balanced. Lamps that allow colours to be reproduced similar to that rendered by daylight are said to have a good ‘colour rendering’.
This is measured on a colour rendering index (CRI) with a scale of 1 to 100 – the best scoring close to 100.
The European standard EN 12464-1 requires that lamps with a CRI of less than Ra80 should not be used in rooms in which people work, or stay, for lengthy periods.
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Colour Temperature
The following table shows a selection from the principal ‘white’ colours, to demonstrate the relation between colour appearance and colour rendering, and to show the systems of proprietary colour names. For the latest ranges of colours it is essential to consult the up-to-date catalogues of individual lamp manufacturers.
Triphosphor Multi-Phosphor Colour Colour Colour Rendering Group Colour Rendering Appearance Temperature 1b 1a
Blue Sky 17000K 8xx (1) -
Skylight 8000-10000K 880 -
Northlight/ 6000-6500K 860 & 8652 956 Cool Daylight
Daylight 5000-5500K - 950 & 954
Cool White 4000K 8402 940
Intermediate 3500K 835 -
Warm White 3000K 8302 930
Very Warm 2700K 827 -
1 There is no standard format (nomenclature) for this lamp series but CRI > 80 2 Special lower energy versions of these lamps are available
Nomenclature of Colour
The colour appearance of the white fluorescent lamps is defined with a 3-digit code which utilises a combination of colour rendering and temperature as follows:
1st Digit = Colour Rendering Index 2nd & 3rd Digits = Colour Temperature e.g. 9 = Ra 90-100 e.g. 27 = 2700K 8 = Ra 80-89 35 = 3500K 5 = Ra 50-59 60 = 6000K
For example: Colour Rendering – 80 on the CRI scale is abbreviated to ‘8’, but indicates that CRI maybe anywhere between 80 and 89. Colour Temperature – 3,500 Kelvin is abbreviated to ‘35’. Thus, the lamp is denoted as ‘Colour 835’
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Application
Tubular fluorescent Lamps are well suited to Commercial Applications such as Offices, Car Parks, and General Retail Lighting.
Where previously, colour appearance was largely a matter of taste, this has now become a critical factor in lamp selection, particularly in the working environment. The general preference is to use cool colours (4,000 Kelvin) for a business-like atmosphere (e.g. in offices, factories, shops), and warm colours for a social atmosphere (e.g. in restaurants and the home).
The most popular choice for offices is triphosphor light colour 835 (white). With a colour temperature of 3,500K it strikes a balance between cool and cosy.
To create a bright and cosy atmosphere, triphosphor light colour 830/930 (warm white) is often the preferred choice with a colour temperature of 3,000K. Applications include shops, schools, meeting rooms, offices, auditoriums, etc.
The warmest light, with a colour temperature of 2,700K, is triphosphor light colour 827 (extra warm white). It is most commonly used in hotel foyers, restaurants and theatres to create a relaxing atmosphere. This would be most ideal for use in the home.
To generate a cooler light there are principally two options – cool white and daylight. Triphosphor light colour 840/940 (cool white) lies somewhere in between daylight and incandescent light. Typically, it would be a working light for factories, workshops, offices, sports halls, and even shops.
Triphosphor colour 860/865/950/954 (daylight) is ideal for where precise colour matching is required such as at dentists’ practices, reprographic workshops, etc. Some manufacturers also produce a ‘cool daylight’ lamp aimed at the clothing retail market where colour rendering is important for customers.
However, with more investigation into the positive effects of light on the individual, we now see special lamps being used, commonly known as ‘feel-good’ lamps, which offer a colour temperature ranging from 8,000 up to 17,000 Kelvin. These lamps have been shown to alleviate the effects of the SAD syndrome, or ‘winter blues’. The enhanced blue light content and unique phosphor coating generates a light spectrum with an optimal balance between light for vision and blue light to positively influence well-being. Tests show that ‘feel-good’ lighting makes people feel more alert, awake and energized.
Light Output
The light output for a tubular fluorescent lamp is typically measured in Lumens, which is the SI measure of “luminous flux”. This is a measure of the total number of packets (or quanta) of light produced by the light source or ”quantity” of light emitted. When selecting the appropriate tubular fluorescent lamp, the decision will include considering the light emitted or lumens.
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Lamp Operating Temperature
The luminous flux of a fluorescent lamp depends to a considerable extent on the mercury-vapour pressure present in the tube. The pressure is determined by the temperature of the coolest part of the tube, which is usually the wall.
The maximum luminous flux is reached when the wall temperature is 40°C, which for many T8 fluorescent lamps corresponds to an ambient temperature of 25°C. For T5 lamps, the ambient temperature may be closer to 35°C. SEE FIGURE 7. The wall temperature of lamps in closed luminaires can be very much higher. In such conditions a high luminous flux can still be attained by using a suitable amalgam in place of pure mercury.
This has the effect of lowering the mercury pressure and also of keeping it more or less stable over a broad temperature scale.
100 26mm diameter T8 90 16mm diameter T8 80 TL5 70
60
50
40 Lumens %
30
20 TLD 10
0 -20˚ -15˚ -5˚ 0˚ 5˚ 10˚ 15˚ 20˚ 25˚ 30 35˚ 40˚ 45˚
Temperature of air surrounding stabilised lamps C˚
Mercury or Amalgam
Fluorescent lamps need a small quantity of mercury in the gas discharge for light generation. This may be present in liquid or pellet form. Mercury is very effective within a narrow operating temperature. However outside of this range, the mercury-vapour pressure will be affected and hence light output.
Amalgam fluorescent lamps use a low mercury content alloy (amalgam), often in pellet form, to control the mercury vapour pressure and have a number of advantages over equivalent mercury lamps. The use of amalgam technology ensures that the mercury vapour pressure within the lamp is less temperature sensitive than normal liquid mercury lamps.
The mercury vapour pressure varies less with temperature and thus the light output, which is dependant on mercury vapour pressure, remains more stable over a wide temperature range. In most normal mains lighting applications this will give superior performance and is particularly beneficial for the higher running temperatures of more compact luminaires.
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High Efficiency (HE), High Output (HO) and Very High Output (VHO)
Linear Fluorescent Lamps are available in a wide range of types and wattages from 14 to 80 Watt and above. An 18W T8 lamp is the most popular size but will no doubt be superseded by the T5 550mm 14W lamp.
However, aside from standard linear fluorescent, manufacturers also offer various high performance lamps. High efficiency (HE) versions have been developed to maximise light output per watt consumed, offering efficacies up to 104lm/w. High Output (HO) and Very High Output (VHO) lamps offer the highest light output for a given size of lamp.
So a user could choose HO 24W/840 for High Output with a luminous efficacy of 89 lm/w or a HE 14W/840 with a luminous efficacy of 96lm/w for High Efficiency, depending on the particular application.
Efficacy (Efficiency)
Efficacy is the measurement of Light Output / Power Consumed or to put it simply, the light output in lumens produced by a source for each Watt of electrical power supplied to the source. Efficacy is a key measure when determining the efficiency of a light source.
Tubular fluorescent lamps offer a high efficacy so are an excellent choice for office environments where good levels of light and low energy consumption are key factors.
Their efficacy ranges from: 45 lm/W for low wattage or 54 lm/W for low colour rendering for T8 halophosphate Lamps and up to 95 lm/W for T5 triphosphor Lamps with a colour rendering index > 85. Under optimal conditions this can increase to over 100 lm/W (for a T5-High Efficiency 35W lamp operated at 35°C with a high frequency ballast).
Life
The life of a fluorescent lamp is measured in a number of different ways. Two measures tend to be employed: mortality (i.e. the number of operating hours elapsed before a certain percentage of the lamps fail) and lumen output (i.e. the depreciation of the lumen output over time). Both sets of data are useful measures. The rated life of tubular fluorescent lamps can range from 6,000 hours up to 60,000 hours, or more, depending on lamp type and control gear.
They can have a lifetime of up to 23,000 hours for normal T5 lamps (90% service lifetime at 12 hr switching cycle). Special long life lamps also exist where the life time is up to 68,000 hours with the same energy efficiency. Halophosphate lamps have a lifetime of only 6,000 hrs and are soon to be discontinued under the ErP Directive.
All tri-phosphor lamps have a high CRI (typically >80) and are also 20-30% more efficient than halo-phosphor types with low CRIs. Better energy saving can be achieved when the lamps are operated on an electronic HF-ballast, and when daylight controls and presence detectors are used appropriately.
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Energy Savers
Recent developments have seen the introduction of ‘Energy-Saving’ lamps. Based on the standard T8 and T5 tubular fluorescent lamps, with the addition of Xenon gas, these lamps operate at a reduced gas pressure, thereby enabling lower operating voltages and hence lower power consumption. Life is typically the same as a standard triphosphor tube but lumen output is slightly lower than the equivalent standard lamp type. The performance of these lamps is highly dependent on the control gear used in the application.
Dimming
Dimming of fluorescent lighting offers significant benefits; giving users the opportunity to control of their own lighting, and deliver energy savings. HF dimming can be used for: visual needs, personal control, daylight harvesting, scheduling and other control strategies. It can offer distinct advantages related to intelligence, flexibility and two-way communication.
Dimming creates a rich visual experience and adds flexibility to any room, providing the right lighting environment for a variety of activities.
Dimming saves electricity and reduces the demand on HVAC systems. Dimming fluorescent lighting instead of repeated switching helps to maintain expected long lamp life.
Allowing employees to choose light levels for specific tasks results in greater employee comfort and improved performance.
Using occupancy/movement sensors, daylight sensors and automated time-based controls with fluorescent dimming helps to manage the lighting in an entire building and further reduce electricity demand.
There are a number of recognised interfaces for dimming fluorescent lighting. The original HF dimming electronic gear had a 1-10V dc control input which altered the light output in proportion to the applied voltage. This is often referred to as an analogue interface.
A digital alternative called DSI (digital serial interface) was developed in order to offer more consistent dimming across a large number of HF ballasts operated by one channel.
This technology formed the basis of the new industry standard, DALI (Digital Addressable Lighting Interface), which has been introduced to allow the use of equipment from multiple vendors without compatibility problems. In effect DALI adds to the intelligence of the ballast by giving it an address and permitting two-way communication with a control system.
EMF
Today, our society uses a huge variety of electrical equipment to make life more comfortable. However, every piece of electrical or electronic equipment creates an electromagnetic field (EMF) in the close surrounding area of the equipment within which it operates.
This also applies to electric lamps. EMF emitted by fluorescent lamps are well within safety limits. European scientific experts identified no health impact from EMF emitted by fluorescent lamps. LIA member companies are committed to, and responsible for, ensuring that all of their products meet the appropriate quality and current EMC standards.
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Control Gear (Ballasts)
All gas discharge lamps, including fluorescent lamps, require a ballast (or control gear) to operate. The ballast provides a high initial voltage to initiate the discharge, then rapidly limits the lamp current to safely sustain the discharge. Lamp manufacturers specify the required electrical input characteristics (lamp current, starting voltage, current crest factor, etc.) to achieve rated lamp life and lumen output specifications.
Two different types of ballast are presently being used to drive fluorescent lamps – electro-magnetic and electronic. With the same input power, a fluorescent lamp can deliver more light using high frequency input signals, which means there is a higher system efficiency and hence energy conservation.
This gain in overall efficiency can be utilised to provide either lower power consumption for the same light output or additional light output for the same power input (compared to 50Hz control gear). Normally the choice is to reduce power for the same light output.
Moreover, a lamp generates virtually no flicker with a high frequency input. Therefore, since electronic ballasts provide better light quality and save energy, they have become more and more popular, and it has become desirable to replace magnetic ballasts with electronic ballasts.
Lumens %
Frequency Hz
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Magnetic/Switch Start Ballast
Magnetic ballasts are inefficient compared to electronic ballasts. They use more electricity in operation and operate at higher temperatures than electronic ballasts. Because of the large inductors and capacitors that must be used, Magnetic ballasts tend to be large and heavy. They commonly also produce acoustic noise (line-frequency hum).
To operate a fluorescent tube using a magnetic ballast also requires a starter and possibly a power factor (PF) capacitor (to correct PF to 0.95).
High Frequency Ballast
% rated life
Frequency of switching per 24 hours Switching frequency and electrical life of fluorecent lamps. Note: This curve is for switch start circuits. Modern High Frequency circuits which provide preheating will reduce the effect of switching upon lamp life
An electronic ballast uses solid state circuitry to provide the proper starting and operating conditions to power one or more fluorescent lamps. Electronic ballasts usually change the frequency of the power from the standard mains (e.g., 50 Hz in UK) frequency to between 20,000 and 50,000 Hz, substantially eliminating the stroboscopic effect of 100Hz flicker (a product of the line frequency) associated with electro-magnetic geared fluorescent lighting.
In addition, because more gas remains ionized in the arc stream, the lamps actually operate at about 9% higher efficacy above approximately 10 kHz. Lamp efficacy increases sharply at about 10 kHz and continues to improve until approximately 20 kHz.
Instant (or ‘cold’) start Ballast
An instant start ballast starts lamps without heating the cathodes at all by using a high voltage (around 600 V). It is the most energy efficient type, but gives the least number of starts from a lamp as emissive oxides are blasted from the cold cathode surfaces each time the lamp is started. This is the best type for installations where lamps are in continuous use or at least not turned on and off very often. These types are not compatible with lighting controls using movement sensors.
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Rapid start Ballast
A rapid start ballast applies voltage and heats the cathodes simultaneously. It provides superior lamp life and more cycle life, but uses slightly more energy as the cathodes in each end of the lamp continue to consume heating power as the lamp operates. A dimming circuit can be used with a dimming ballast, which maintains the heating current while allowing lamp current to be controlled.
Programmed start Ballast
A programmed-start ballast is a more advanced version of rapid start. This ballast applies power to the filaments first, then after a short delay to allow the cathodes to preheat, applies voltage to the lamps to strike an arc. This ballast gives the best life and most starts from lamps, and so is preferred for applications with very frequent power cycling such as communal areas and toilets with occupancy sensors.
Choice of Ballast
16 mm diameter T5 fluorescent tubes are designed to operate only from dedicated high frequency electronic control gear. Both krypton filled and argon filled 26mm diameter T8 fluorescent lamps can be operated on HF control gear, the former at reduced wattage from their marked value.
Emergency Lighting
Until recently, linear fluorescent lamps have been the preferred choice for emergency lighting. Because of their long life, high efficiency and virtually maintenance free, LEDs are increasingly being used in emergency lighting.
TECHNICAL
Burning Position
Linear fluorescent lamps can be used in Universal burning position i.e. in any position, vertical or horizontal without detrimental effect to their performance.
Run Up or Start Up time
The run-up time of a fluorescent lamp will vary dependent on the lamp selected, particularly whether it contains Mercury or Amalgam. In general, a Mercury lamp will come to full light output quicker than Amalgam. Ballasts are also a significant factor because a wide choice of electronic ballasts are now available, which enables the specifier to select a unit to suit the particular application, and each type has different characteristics.
Re-strike time (Rapid Switching)
In general, linear fluorescent lamps can be switched on and off but the rated life will be reduced by frequent switching. However, certain ballasts i.e. ‘warm-start’ has been designed to lessen the load on linear fluorescent lamps, thereby reducing lumen depreciation and hence life. Also, the use of the lamp also affects its service life and hence, although there may be more frequent switching events, its overall installed life may still be lengthened by a lighting control system.
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Supply Voltage
Recommended operating range best performance
Lamp Volts Lamp Watts
Volts & Currnent Volts Lamp Lumens Percent Lumens, Watts, Percent
Lamp Current
Percent of rated ballast voltage
All lighting equipment is designed to work best at a specific voltage (230VAC for Europe) and any variations in supply voltage to the fixture may be the result of fluctuations in the building’s power distribution system or a voltage reduction programme initiated by the energy provider.
Higher or lower voltage supplied to the ballast affects lumen output and input wattages. Generally, a ballast receiving a high supply voltage produces high lumen output at the expense of an increase in input wattage. Conversely, a ballast receiving a low supply voltage would produce a lower lumen output with a reduction in input wattage. Electronic ballasts are not as sensitive to small variations in supply voltage. Some newer versions provide constant lumen output variations of up to + or -10% fluctuations in supply voltage.
All lighting equipment is designed to work best at a specific voltage (230VAC for Europe) and any attempt to supply outside the harmonised limits will invalidate warranty.
HEALTH
Frequency
Some consumers are concerned about medical problems such as epileptic fits, or mental disturbances (e.g. migraines) caused by fluorescent lamps. A small number of cases have been reported by people who suffer from reactions to certain types of linear fluorescent lamps. In the majority of these cases, the lamps in question were used in offices, restaurants (in certain European countries) and in limited places in domestic households (such as kitchens and garages)
These isolated cases were almost certainly triggered by OLD technology which operated on a conventional (Copper-Iron) ballasts with a low frequency - usually 100Hz; this is not the case with new energy efficient linear fluorescent lamp technology which, unlike earlier energy efficiency technologies, operates on high frequency drivers (50kHz). Health related problems can be reduced, or avoided, if consumers opt for new technologies using high frequency drivers.
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Mercury
Mercury is an essential component in the function of fluorescent lamps. The EU ROHS Directive limits the levels of Mercury to no more than 5mg per lamp. No mercury is released when the lamps are in use and they pose no danger when used, and recycled, properly.
However, fluorescent lamps are made of glass tubing and can break if dropped or roughly handled. Care should be taken when removing the lamp from its packaging, installing it, or replacing it.
Other types
Other types of fluorescent tube are T5 and T9 ‘ring’ or ‘circular’ lamps, offering the same benefits as the linear T5 & T8 types but in a circular format. This alternate shape, allows luminaires to be designed which are more compact and stylish.
Ultra-slim 7mm diameter (T2) lamps are available for special applications where unobtrusive light sources are required e.g. under shelf lighting, picture lighting and display cabinet lighting. T2 lamps may actually be joined together to create a block of lamps, giving a higher light output, compared to T5 lamps of the same dimensions.
Shatterproof
Shatterproof tubes are used in factories and workshops and in particular food processing industry where there can be no possibility of glass fragments getting into the products.
Basically, they are a normal fluorescent tube with an additional outer skin designed to contain the contents of a lamp if broken.
Advantages
Linear fluorescent Lamps provide high colour rendering, near constant light output throughout their life, are highly efficient, low-cost in terms of both initial expenditure and running costs, and offer a long life.
Disadvantages
Linear Fluorescent Lamps are quite fragile, having a thin glass wall and delicate internals. All linear fluorescent lamps contain small quantities of Mercury which needs to be disposed of correctly at end of life or if the tube is shattered. Linear fluorescent Lamps also require a ballast which adds cost to the lighting package.
Key Properties
Efficiency Control CCT K CRI Ra Dimmable Starting Re-start Cost lm/W Gear 2700 - Ballast Medium - 60-106 100 Yes Prompt Prompt 6000K and Starter Low
Standards
• BS EN 61195: Double-capped fluorescent lamps. Safety specifications • BS EN 60081 : Double-capped fluorescent lamps - Performance specifications
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Compact Fluorescent Lamps
Compact fluorescent lamps (CFLs) have the characteristics and advantages of linear fluorescent lamps, but with compact size. Lamp designers have been able to fold the discharge path to reduce the overall size of the lamp, whilst retaining high efficacy. The phosphors used are triphosphors.
As with tubular fluorescent lamps, CFLs consist of a circular glass tube but bent into a more compact shape, coated on the inside with fluorescent phosphors. CFLs contain a dose of mercury in liquid or pill form and a mixture of inert gases. At either end of the tube are electrodes (cathodes) which pass an electrical charge from one end to the other, exciting ions in the process.
There are two types:-
• Single capped CFLni - Compact Fluorescent Lamp – Non-Integrated Ballast • Self ballasted CFLi - Compact Fluorescent Lamp - -Integrated Ballast
Unlike, linear fluorescent Lamps, where they are of a standardised length and diameter, CFL manufacturers have perfected their own designs of CFL, so you will see differences in the shape and size of the glass envelope and base. The glass tubes may comprise of a single, double, triple, or even quadruple tube which may be linear, tubular or in the case of CFLis, various other shapes.
The individual glass tubes are joined together to enable the discharge to pass from one cathode to another. Some versions are enclosed in an outer envelope to more closely resemble the lamps they are designed to replace.
Compact Fluorescent Lamp – Non-Integrated Ballast (CFLni)
Compact Fluorescent Lamps are highly energy-efficient, low-pressure discharge lamps with a phosphor coating to transform the mercury UV radiation into visible light.
CFLni’s utilize specific pin based fittings (see below) to enable connection to separate control gear. High quality ballasts last longer than the lamps and can enable greater energy savings as well as control options such as dimming, daylight control and presence detection.
A further environmental benefit over integrated lamps is the fact that when a lamp fails the ballast is not thrown away and can be used to operate a replacement lamp. Credit: Osram Ltd.
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Type
CFLnis require separate control gear and are split into 2 main categories:-
• 2-Pin – with an integral starter in the base – these operate on a magnetic ballast. The 2 pin product is scheduled for phase out in Europe under the Energy Using Products Directive. • 4-Pin – utilising separate control gear and starting device and are designed for operation on high frequency control gear. These lamps can be used for emergency lighting luminaires and where dimming is required.
Quad Lamp Triple-twin F-Lamp
2-D Twin-Tube Circline
Size
When luminaire manufacturers are designing fixtures, the size of the lamp is of critical importance. CFLni lamps utilize a T4 tube diameter. The smallest CFLni would be a 5W twin-tube (single) lamp which would enable the design of a very small compact fixture. The largest CFLnis are multiple tube lamps which are designed to replace HiD lamps, for example, in swimming pools where maintenance and instant restrike are key decision making factors.
Light Output
The light output for a CFLni lamp is typically measured in Lumens, which is the SI measure of “luminous flux”. This is a measure of the total number of packets (or quanta) of light produced by the light source or ”quantity” of light emitted. When selecting the appropriate CFLni, the decision will include considering the light emitted or lumens.
Wattage
The wattage of a CFLni ranges from as little as 5W for a ‘single’ 2-pin lamp, through the most popular 26W double’ to the most powerful 80W ‘long’ lamp. There are now CFLni lamps with multiple tubes, offering up to 120W rating.
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Efficacy
A typical efficacy for a CFLni would be between 50 lm/w and 70 lm/w. This is a critical threshold for lamp makers as it is the minimum level to meet Part L of the Building Regulations. Also, when comparing CFLni lamps to linear fluorescent in office applications.
Lumen Maintenance
As CFLni benefit from further development, lumen maintenance is improving. The IEC standards stipulate lumen maintenance to be over 75% after 10,000 hours.
Energy Savers
More recent developments have seen the introduction of ‘Energy-Saving’ versions. Based on the standard lamps, these lamps operate at a reduced gas pressure, thereby enabling lower operating voltages and hence lower power consumption. Life is typically the same as a standard tube. Lumen output is slightly lower than the equivalent lamp type.
Dimming
The majority of CFLnis are used in internal applications such as offices and corridors. As with linear fluorescent lamps, dimming of fluorescent lighting offers significant benefits; giving users control of their own lighting, and energy savings. Digital dimming can be used for: visual needs, personal control, daylight harvesting, scheduling and other control strategies. It can offer distinct advantages related to intelligence, flexibility and two-way communication.
Cap
There are a wide range of codes for the cap types on plug in CFLnis. The table opposite lists these. 2 Pin 4 Pin
G24d-1 G24q-1 G28d
The newest development is the G28d plug-in cap which G24d-2 G24q-2 has been developed to reduce the length and size of the G24d-3 G24q-3 lamp holder, as well as the operating temperatures of the lamp in the fixture. This will mean that more compact GX24d-1 GX24q-1 fixtures can be designed.
There are also possibilities of introducing CFLni lamps GX24d-2 GX24q-2 into the domestic market. By enabling plug-in CFLs to be used in the residential market, a replaceable ballast can be GX24d-3 GX24q-3 used, either incorporated into the lamp holder or separately in the fixture. Ballasts tend to have a longer life than the - GX24q-4 lamp which means that the lamp can be replaced thereby reducing material going into the waste-stream. - GX24q-5
Application
CFLnis enable the design of new compact, energy efficient luminaires. Long length CFLs such as the CFL-L lamp with 2G11 base are now replacing 3 or 4 600mm (2ft) T8 linear fluorescent lamps in modular office fittings, as 1 single CFLni is rated at 80W and offers an efficacy of 85 lm/W. The CFLni is more popular for with professional users, for example in lighting such as offices and public buildings. However, high Frequency control gear is now available integrated into CFL lampholders, making luminaire conversion from GLS to CFL a relatively simple procedure.
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HIGH INTENSITY DISCHARGE
How it works
A high intensity discharge (HiD) lamp works by means of a discharge of electricity at high voltage between two electrodes, which results in a bright light being emitted by excited molecules of substances caught in the electrical arc.
Light of various colours and intensities at various efficacies can be produced by discharging electricity through the arc tube which contains vapourised metals such as mercury and sodium, at various pressures. The arc tube is contained in an outer envelope where the shape is dependent on the application.
Ballasts
Like fluorescent lamps, the characteristics of high pressure sodium, metal halide and mercury vapour HiD lamps require aballast to start and maintain their arcs. Ignitors are additionally required for sodium and metal halide lamps. Furthermore, to compensate blind current when using magnetic ballasts, compensation capacitors must be fitted. Lamps that are not operated within the optimal performance range will not produce proper light output or experience full life. There are several ballast types to provide proper control, but offer differing lamp wattage regulation, voltage dip tolerance, power loss and cost. The method used to initially strike the arc varies: mercury vapor lamps and some metal halide lamps are usually started using a third electrode near one of the main electrodes while other lamp styles are usually started using pulses of high voltage.
As well as stabilising the lamp´s operating point, ballasts also influence the lamp´s output and luminous flux, the system´s light output, the service life of the lamps as well as the colour temperature of the light.
Electromagnetic or electronic ballasts can be used for high-pressure discharge lamps. Unlike with fluorescent lamps, lamp efficiency is not decisively altered by the use of electronic ballasts. In contrast, electronic ballasts lead to a reduction of the inherent losses and thus to an increase in system efficiency. In addition, electronic ballasts ensure gentle lamp operation, which increases the lamp´s service life.
Independent electronic and electromagnetic ballasts have also been developed, which in the form of control gear units then provide special advantages during application.
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Restrike Time
As high-pressure lamps operate with a start-up phase, the lamp´s full luminous flux will only be reached after this start-up period. In the event of mains interruptions, this start-up time can be prolonged depending on the lamp´s temperature. If an additional source of light is desired or required for this start-up period for safety-relevant applications, it is possible to switch on an auxiliary lamp with the help of a start-up switch.
Lamp Family Typical start-up time Typical restart time (mains interruption at lamp operating temperature)
HS 3 min 5 min
HI / C-HI 3 min 10 min
HM 4-5 min 4-5 min
LS 10 min 5 min
Lamp Replacement
Lamps of different makes are not necessarily interchangeable, either visually or electrically. Compatibility between lamp and control gear should always be checked with the individual manufacturers.
Low Pressure Sodium
Low pressure sodium (LPS) lamps, also known as sodium oxide (SOX) lamps, consist of an outer vacuum envelope of glass coated with an infrared reflecting layer of indium tin oxide, a semiconductor material which allows visible lightwavelengths to pass and reflects infrared back, keeping it from escaping. The lamp has two inner borosilicate glass U-pipes containing solid sodium and a small amount of neon and argon gas https://en.wikipedia.org/wiki/Penning_mixture to start the gas discharge. When the lamp starts (i.e. when the arc strikes) it emits a dim red/pink light to warm the sodium metal and within a few minutes turns into the familiar bright yellow/orange colour, as the sodium metal vaporises.
Colour Rendering
LPS lamps produce a virtually monochromatic light averaging at a 589.3 nm wavelength (actually two dominant spectral lines very close together at 589.0 and 589.6 nm). As a result, the colours of illuminated objects are not easily distinguished since they are seen almost entirely by their reflection of this narrow bandwidth yellow/orange light. This is close to the maximum sensitivity of the human eye at normal lighting levels, and the efficacy is the highest of all lamp types but with very poor colour rendering.
Colour Temperature
LPS lamps have a colour temperature of 2,000 Kelvin.
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Application
LPS lamps are mainly used for exterior applications such as road lighting and security lighting. At low lighting levels such as secondary road lighting the eye response changes and the use of white light sources is replacing SOX lamps particularly in amenity areas and pedestrianised shopping centres. SOX-E lamps give improved efficacy with lower power consumption and SOX-PLUS lamps have a longer life. SOX-E and SOX-PLUS lamps give optimum performance only when used with appropriate control gear.
Efficacy
LPS lamps are the most efficient electrically-powered light source when measured for photopic lighting conditions—up to 200 lm/W, primarily because the output is light at a wavelength near the peak sensitivity of the human eye. As a result they are widely used for outdoor lighting such as street lights and security lighting where faithful colour rendition is considered less important.
Wattage
LPS lamps are available with power ratings from 10 W up to 180 W; however, longer bulb lengths create design and engineering problems.
Life
LPS Sodium lamps have an average life of 15,000 to 20,000 hours.
Lumen Maintenance
Unlike other lamp types, LPS lamps do not decline in lumen output with age. For example, Mercury vapour HiD lamps become very dull towards the end of their lives, to the point of being ineffective and yet they continue to consume full power. LPS lamps, however do increase energy use slightly (about 10%) towards their end of life.
Type
LPS lamps are more closely related to fluorescent than high intensity discharge lamps, since they have a low–pressure, low–intensity discharge source and a linear lamp shape. LPS lamps tend to be available in tubular form.
Cap
Cap types tend to be E27 or E40 for the larger wattages
Starters
Lamps only require 700V for reliable ignition and electronic starters are therefore compact, simple and relatively inexpensive. Although LPS Lamps can be used with a standard reactor circuit and therefore will require an ignitor, many LPS control gear circuit operate on a leak-transformer ballast system. By default, this generates the 700V sufficient to start the lamp and in this instance an ignitor is not required.
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Restrike Time
Like fluorescent lamps, LPS lamps do not exhibit a bright arc as do other HID lamps; rather they emit a softer luminous glow, resulting in less glare. Unlike HID lamps, which can go out during a voltage dip, low pressure sodium lamps restrike to full brightness rapidly.
Advantages
One unique property of LPS lamps is that, unlike other lamp types, they do not decline in lumen output with age. As an example, mercury vapor HID lamps become very dull towards the end of their lives, to the point of being ineffective, while continuing to consume full rated electrical use.
Disadvantages
LPS lamps do increase energy usage slightly (about 10%) towards their end of life, which is generally around 18,000 hours for modern lamps. The obvious disadvantage with LPS lamps is the yellow/ orange monochromatic light output.
Standards
• BS EN 62035: Discharge lamps (excluding fluorescent lamps). Safety specifications • BS EN 60192: Low pressure sodium vapour lamps. Performance specification
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High Pressure Sodium
Electrode Alumina arc tu e
Arc
Sodium mercur amalgram
A.C. voltage Ballast
How it works
The light is generated by an electrical discharge in a gas containing sodium and mercury (sodium amalgam), contained in an arc-tube. Because of the extremely high chemical activity of the high pressure sodium arc, the arc tube is typically made of translucent aluminum oxide.
Xenon at a low pressure is used as a “starter gas” in the HPS lamp. It has the lowest thermal conductivity and lowest ionization potential of all the non-radioactive noble gases. As a noble gas, it does not interfere with the chemical reactions occurring in the operating lamp. The low thermal conductivity minimizes thermal losses in the lamp while in the operating state, and the low ionization potential causes the breakdown voltage of the gas to be relatively low in the cold state, which allows the lamp to be easily started.
High pressure sodium (HPS) lamps are smaller than LPS lamps. They produce a dark pink glow when first struck, and a pinkish orange light when warmed. Some lamps also briefly produce a pure to bluish white light in between. This is formed by the mercury glowing before the sodium is completely warmed.
The higher vapour pressure results in a broader spectrum of colour being emitted and hence colours of objects under these lamps can be distinguished.
HPS lamps are known as SON lamps – SON is the variant for “Sun”. Mercury-free lamps are available and provide similar performance to equivalent existing standard ILCOS S lamps.
Twin arc tube lamps are also available which extend lamp life and provide more rapid hot restarting. However as the arc tubes are off the lamp central axis this may alter the light output and distribution in some luminaires.
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Colour Rendering
HPS lamps would be specified in areas where good colour rendering is important, or desired. Low wattage ILCOS SM and SH lamps operate at a higher sodium pressure. They are designed for display lighting and have significantly bettercolour rendering (CRI 85/Group 1B) but with reduced efficacy and life. De Luxe (Comfort) versions have improved colour rendering (CRI 65/Group 2) but give slightly lower light-output.
Colour Temperature
LPS lamps have a colour temperature of 2,000 Kelvin. A variation of the high pressure sodium, the White SON, introduced in 1986, has a higher pressure than the typical HPS/SON lamp, producing a colour temperature of around 2700 K, with a CRI of 85; greatly resembling the colour of an incandescent light.[2] These are often indoors in cafes and restaurants to create a particular atmosphere. However, these lamps suffer from higher purchase cost, shorter life, and lower light efficiency.
Application
HPS lamps are used for road lighting, for floodlighting and industrial interior lighting. They also have some commercial applications, e.g., for sports halls and public concourses. Standard versions offer high efficacy and long life. Understanding the change in human colour vision sensitivity from photopic to mesopic and scotopic is essential for proper planning when designing lighting for roads. HPS Lamps are favoured by indoor-growers for general growing because of the wide colour-temperature spectrum produced and the relatively efficient cost of running the lights.
Efficacy
High pressure sodium lamps are quite efficient—about 100 lm/W—when measured for photopic lighting conditions. ‘Super’ or ‘Plus’ versions, for exterior and industrial applications, have a significant increase in light output and lumen maintenance compared with Standard Low Pressure Sodium lamps.
Wattage
Lamps range from 35W up to 1000W and are all applicable for use with Single Phase supplies. Lamps of 100W and below are also available for use on 110V supplies. From 600W and above, lamps are also available for use on Cross (X) Phase supplies.
Life
The rated life of HPS lamps varies depending upon wattage and also whether lamps are standard or High Output types. For standard and High Output lamps; 50W and 70W life figures up to 28,000 hours can be achieved and for lamps 150 – 600W life is increased to 32,000 hours. However, it must be noted that higher wattage/High Output lamps have a slightly reduced life by some 3,000 hours. A 1000W High Output can typically achieve 18,000 hours. HPS Lamps which are designed to offer a better colour rendering Ra have a much reduced life reaching approx 24,000 hours.
Lumen Maintenance
Wattage and design greatly influence lumen maintenance. High Output lamps trade their increase in lumens for a reduction in Lumen maintenance. For lamps between 150W and 400W expect 90% with the 50W and 70W following close behind at 88% and the 600W at 85%. For High Output lamps we can expect 80% for the 50W and 70W with 85% for the 150W – 400W range reducing further to 80% for the 1000W. Finally high Ra lamps are reduced 78%
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Type
HPS sodium lamps tend to be:
• Elliptical • Tubular • Double Ended • Reflector
Cap
Cap types tend to be E27 or E40 for the larger wattages
Starters
SON lamps are available with 2 methods of starting:
• lamps with an internal ignitor are marked • lamps requiring an external ignition device are marked
There is also a range of ‘plug-in’ high pressure sodium lamps designed to replace high pressure mercury lamps with ballasts, which comply with BS EN 60922/923. (Some ballasts may not have adequate insulation between windings.) Small changes may be required to ballast tapping, values of PF capacitor, or to some wiring. Reference should be made to the technical literature of lamp manufacturers.
Restrike Time
The re-strike time for all HID lamps is based solely on the technology of the lamp and the time taken for the lamp to cool down to a sufficiently low temperature that then enables the lamp to be restarted. Normally for an HPS lamp in an open fixture such as a High-Bay luminaire this will be less than a minute. Additional time should be allowed when lamps are embodied in a heavy case Floodlight, for example.
Advantages
HPS lamps are very much a commodity light source, readily available from numerous sources and manufacturers. They have an established history of reliability and offer long life and good lumen maintenance. They are reasonably simplistic in their design and operate over a wide temperature range.
Disadvantages
Although considered by some as an acceptable light source in terms of colour temperature and colour rendering, HPS has a narrow spectral distribution and therefore visual acuity is poor. Lamps can cycle towards end of life.
Standards
• BS EN 62035: Discharge lamps (excluding fluorescent lamps). Safety specifications • BS EN 60662: Specification for high-pressure sodium vapour lamps
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High Pressure Mercury
Outer ul
P osp or
Arc Tu e Starting Electrode
Starting Resistor
Cap
How it works
A high pressure mercury discharge lamp operates in a quartz arc tube. MBF(HPL-N, HQL) lamps have an outer ellipsoidal bulb with an internal phosphor coating, which improves the colour rendering. MBFR (HPL-R, HQL-R) lamps have a shaped outer bulb with an internal reflector coating.
Note
MBTF (ML,HWL) is a mercury discharge tube connected in series with a tungsten filament in the same outer bulb: external control gear not required.
Colour Rendering
De Luxe versions with improved colour rendering have a special phosphor coating.
Colour Temperature
Standard HPMV lamps have a nominal colour temperature of 4000K, where other blended or De Luxe lamps have a colour temperature circa 3400K.
Application
Mercury lamps were used for illuminating road signs and industrial lighting but have largely been replaced by more efficient lamps now available. They are more predominantly used in mainland Europe but will soon be replaced as part of ErP Directive.
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Efficacy
Mercury lamps offer low cost discharge lighting where high efficacy is not important. The lamps incorporate a third electrode for starting and so the control gear to operate mercury lamps is only a ballast and power factor correction capacitor. No external ignitor is required.
Wattage
Standard mercury lamps are available in 50W, 80W, 125W, 250W, 400W, 700W and 1000W wattages. Blended mercury lamps tend to be 160W, 250W and 500W. All lamp types are suitable for Single phase supply with the 700W and 1000W also available for use on a Cross-Phase supply.
Life
The life of HPMV ranges from 12,000 hours for the lower wattage 50W and 80W with the remaining wattages being 15,000. Blended lamps are only 8000 hours.
Lumen Maintenance
HPMV lamps have inherently poor lumen maintenance; 50% is normal with some lamps dropping to 40%.
Type
HPMV lamps are always coated and therefore will be elliptical in shape. There is also a range of reflector lamps.
Cap
HPMV lamps utilise standard E27 and E40 bases although a tri-pin bayonet cap is also used on lower wattages. This B22d-3 lamp cap is similar to the standard household incandescent lamp cap but has three pins equally spaced at 120 degrees apart, preventing its use directly into a mains circuit.
Starters
By the nature of their design HMPV lamps do not require any starting aids or ignitors and successfully start up on their own.
Ballasts
Ballasts (often called Chokes) are part of the operating “gear” for Mercury “Discharge Lamps”. There is no one ballast solution for metal halide lamps - they either run on Sodium gear or Mercury gear so it is imperative to match the ballast with the corresponding lamp.
Restrike Time
A hot lamp will take between 4 and 7 minutes depending upon the thermal mass of the luminaire.
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Advantages
HPMV lamps are cheap, readily available and do not require a starting device. They are normally very tolerant of mains supply variations with regards to life. Although they do have an average life rating, some models can in some circumstances appear to operate for many years.
Disadvantages
Very poor light output and poor lumen maintenance.
Standards
• BS EN 62035: Discharge lamps (excluding fluorescent lamps). Safety specifications • BS EN 60188: High-pressure mercury vapour lamps. Performance specifications
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Metal Halide Lamps
Starter Electrode
Pinc Fin
Electrode
Arc C am er E auset Tip
Electrode
Pinc Fin
How it works
Metal Halide lamps are the most advanced high pressure discharge lamps. They have quartz or sintered alumina (ceramic) arc-tubes. Most lamps have an outer glass bulb. Like other gas-discharge lamps, metal halide lamps produce light by passing an electric arc through a mixture of gases. In a metal halide lamp, the compact arc tube contains a high-pressure mixture of argon, mercury, and a variety of metal halides. The mixture of halides will affect the nature of light produced, influencing the correlated colour temperature and intensity (making the light bluer, or redder, for example).
The argon gas in the lamp is easily ionized, and facilitates striking the arc across the two electrodes when voltage is first applied to the lamp. The heat generated by the arc then vaporizes the mercury and metal halides, which produce light as the temperature and pressure increases. Common operating conditions inside the arc tube are 70-90 PSI (480-620 kPa) and 1090 °C.
Lamps with very low ultra violet output have now been introduced which incorporate UV absorbing quartz. These do not require external UV filters on the luminaires. Metal halide lamps of the ‘protected’ type are now available for operation in luminaires without safety screens. Fragments from a shattered lamp are prevented from leaving theluminaire, either by suppressing the violence of the exploding arc-tube by the inclusion of an open-ended quartz tube surrounding the arc-tube, or by using a PTFE coating on the outer bulb to maintain the integrity of the lamp in the event of a shattered arc-tube.
Compact Metal Halide lamps invariably utilize ceramic technology. Ceramic arc tubes are more stable than quartz and offer improved life, efficacy and colour rendering.
Like all other gas discharge lamps, metal halide lamps require auxiliary equipment to provide proper starting and operating voltages and regulate the current flow in the lamp.
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Colour Rendering
Depending on the mix of elements, there is a wide range of efficacy and/or colour appearance.
• Elliptical or Tubular Quartz lamps are generally good at 68-70 Ra • Compact Ceramic Metal Halide lamps can be as high as 95+ Ra
Colour Temperature
Typical colour temperatures would be in the range 3,700 – 4,000K, although some lamps can be up to 10,000K. ‘Ceramic’ arc-tube metal halide lamps have improved colour stability throughout their life. Colour temperature variance is seen greatest in “probe start” technology lamps (±300 K). Newer metal halide technology, referred to as “pulse start,” has improved colour rendering and a more controlled variance (±100 to 200 K).
Application
Metal halide lamps are mainly used in commercial interiors, industry and floodlighting, as well as for colour TV lighting in stadia and studios. Smaller ratings are used for retail lighting.
Metal halide lamps, which can be retrofitted into high pressure sodium lamps installations, are specifically manufactured to be dimensionally and electrically compatible with the replaced lamp. It is relatively easy to replace HPS lighting with Metal Halide lamps as most Metal Halide lamps can operate directly from existing HPS control gear. Even ‘difficult’ 70W HPS lamps with internal starters can be directly replaced, using a simple conversion kit.
Efficacy
About 24% of the energy used by metal halide lamps produces light (65-115 lm/W), making them generally more efficient than fluorescent lamps, and substantially more efficient than incandescent bulbs.
Wattage
Due to the broad range and types available, metal halide lamps are available in 20W up to 3,500W.
Life
Metal Halide lamps tend to average life of 10,000 – 15,000 hours
Lumen Maintenance
Dependent on the various technologies that are available to produce a metal Halide lamp; maintenance figures of between 60% and 90% are possible - the latter associated with the latest technology lamps.
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Type
Metal Halide lamps have been developed to suit many applications both internal and external. Consequently, a variety of shapes are available:-
• Elliptical • Tubular • Double Ended • Compact Pin ended and Reflector
Cap
Metal Halide Lamps have an E27 or E40 screw in Edison cap.
Finish/Coating
Metal Halide Lamps are available in clear or coated glass.
Starters
Old technology “standard” MH lamps - typically those originally produce to operate on CWA (Constant Wattage Autotransformer ballasts and lamps with penning mix and other similar technologies - are able to ignite with a relatively low ignition pulse of 600V.
High technology lamps (which normally assumes lamps with a higher arc tube pressures such as Ceramic Metal Halide and Quartz) require ignition voltages of 3.0KV although some low wattage lamps only require 1.8kV.
High wattage Double Ended lamps may require 5-6KV.
As with HPS lamps Metal Halide starters are available in different forms:
• Two Wire low voltage; connecting directly across the lamp • Three wire SIP (superimposed pulse) connecting in series between the ballast and lamp and Impulser • Semi-Parallel types that utilise tapping points on the ballast to generate the high voltages.
Two wire ignitors are simple and very cost effective but are limited to standard MH lamps.
SIP ignitors are universal and can operate with any lamp and ballast. Because the ignitor also conducts the lamp current and the higher the current the greater the component cost, they are normally designed in wattage ranges, say 35W to 100W, 100W to 400W etc.
Impulser and semi parallel ignitors do not pass lamp current and one small ignitor can suit many lamp wattages. However, the ignitor and ballast must be designed as a package, thus one manufacturer’s ignitor will only operate correctly with that manufacturer’s ballast.
Ignitors can also incorporate timers and lamp cycling counters to shut down the ignitor should a failed lamp remain unattended, thus reducing the stress of applying prolonged high voltage pulses to the remaining control gear.
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Ballasts
As lamp manufacturer´s reference values regarding lamp current and voltage are generally identical for metal halide (HI) and high-pressure sodium lamps (HPS) of the same lamp wattage and the impedance values required for the ballast are also identical, the same ballasts can frequently be used for both lamp types.
HI lamps react sensitively to impedance deviations from the rated value with appreciable colour changes. Modern ballasts therefore comply with the lamp´s narrower tolerances. Moreover, ballasts remain below the maximum peak DC value for HI lamps. This value is not specified for HS lamps; instead, the maximum stated start-up current must not be exceeded.
Restrike Time
A “cold” (below operating temperature) metal halide lamp cannot immediately begin producing its full light capacity because the temperature and pressure in the inner arc chamber require time to reach full operating levels. Starting the initial argon arc sometimes takes a few seconds, and the warm up period can be as long as five minutes (depending upon lamp type). During this time the lamp exhibits different colours as the various metal halides vaporize in the arc chamber.
If power is interrupted, even briefly, the lamp’s arc will extinguish, and the high pressure that exists in the hot arc tube will prevent re-striking the arc; a cool-down period of 5-10 minutes will be required before the lamp can be re-started. This is a major concern in some lighting applications where prolonged lighting interruption could create manufacturing shut-down or a safety issue. A few metal halide lamps are made with “instant restrike” capabilities where the lamp, ballast and socket are built to withstand the 30,000 volt re-ignition pulse supplied via a separate anode wire.
Performance
The colour temperature of a metal halide lamp can also be affected by the electrical characteristics of the electrical system powering the bulb and manufacturing variances in the bulb itself. If a metal halide bulb is underpowered it will have a lower physical temperature and its light output will be ‘cooler’ (more blue, or very similar to that of a mercury lamp).
This is because the lower arc temperature will not completely vaporize and ionize the halide salts which are primarily responsible for the warmer colours (reds, yellows), thus the more-readily ionized mercury will dominate the light output. This phenomenon is also seen during warm-up, when the arc tube has not yet reached full operating temperature and the halides have not fully vaporized.
The inverse is true for an overpowered bulb, but this condition can be hazardous, leading possibly to arc-tube rupture due to overheating and overpressure. Moreover, the colour properties of metal halide lamps often change over the lifetime of the bulb. Often, in large installations of MH lamps, particularly of the quartz arc-tube variety, it will be seen that no two are exactly alike in colour.
Advantages
MH lamps are an excellent white light source. They are readily available from numerous sources and manufacturers, have an established history of reliability and offer reasonably long life and reasonable lumen maintenance. Primarily over other HID sources they have an excellent CRI (Colour Rendering Index) or Ra of more than 60 with some technologies reaching 90.
Latest design technologies are now offering increasing life and lumen maintenance figures approaching some early HPS lamps.
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Disadvantages
Depending on the technology, some MH lamps can be expensive. Arc tubes can rupture at end of life making them only suitable for enclosed luminaires, although protected lamps are available.
Lamps can cycle towards end of life.
Standards
• BS EN 62035: Discharge lamps (excluding fluorescent lamps). Safety specifications • BS EN 61167: Specification for metal halide lamps
New Developments
New, smaller electronically controlled MH lamps are now being developed which can be a building block for ErP compliant systems. Rather than focusing on the light source alone, manufacturers are concentrating on a coupled system where lamp and ballast together can offer significant technological advantages over the existing lighting package.
The lamps are compact in design and offer a pure white light which brings benefits for the luminaire designers and the client, whilst their operation only via an electronic ballast offers superior performance, energy savings and life.
Manufacturers are currently working with both ceramic and quartz technology.
These next generation compact MH lamps enable highly effective white-light street illumination. By producing brighter, warmer white light, they improve the appearance of streets and other urban features and, in the process, provide a safer, more secure environment for residents to enjoy.
Not only do they transformed the ambience of municipal locations, they can reduce energy costs by more than 50% verses traditional high pressure mercury or sodium outdoor lighting.
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INDUCTION LAMPS
Induction is a process whereby the generated power is passed from one circuit to another without the use of physical electrical conductors. Thus induction lamps are also known as ‘Electrode-less’. Induction lamps utilise the same principle as transformers and radio receivers, enabling lamps to be constructed without the need for wire connections to pass through the glass or quartz envelope. This simplifies construction and extends lamp life. Induction lamps are available as low pressure mercury lamps using the same triphosphor coating of the inner bulb surface. Low wattage versions use integral control gear but the higher power ratings have external control gear. There is also a high pressure discharge induction lamp, which uses sulphur vapour.
As the commercially available range is limited and diverse a summary of typical operating characteristics has not been included.
Advantages
Induction lamps are virtually maintenance free and offer an ultra-long life time. They give a pleasing light with high visual comfort - offering a range of colour temperatures.
Disadvantages
Lamp manufacturers have pursued different variations on the induction theme. Consequently, there are a number of different types of lamp available. Due to them being a specialist lamp, their availability and distribution is limited whilst the purchase price is high.
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NEW AND UNUSUAL LAMP TECHNOLOGIES Research and development in the lighting world is continuous with advances being made in existing, emerging and new light sources. This section of the Light Source Guide looks at lighting technologies that are less common or those just emerging from development. Information about the following light sources is included: • Emerging forms of solid state lighting - Organic LEDs, Polymer LEDs and similar developments. • Electrodeless lamps - induction and plasma lighting. • Electroluminescence • Laser
The progress and abilities of each of these lighting technologies are described below.
Emerging forms of solid state lighting (OLEDs and PLEDs)
Solid state lighting is not restricted to conventional LEDs but extends to a range of planar devices generically known as Organic Light Emitting Diodes – OLEDs. These devices operate on similar principles to LEDs but have a very different form factor, which is made up from layers of organic materials sandwiched between an anode and a cathode. Currently there are two development approaches being pursued to bring OLEDs to the market:
• Small molecule OLEDs, which are sometimes referred to as SM-OLEDs; and • Polymer OLEDs known generally as PLEDs, which use a thin film polymer structure.
Figure 1 shows a typical cross-section through both structures. Both devices offer extended emissive surfaces which are already being exploited in the visual display market.
PLED lighting is formed by Cathode A Single EIL (electron transport la er) Emissive Layer ETL (electron transport la er) EML (emissi e la er) lue EML (emissi e la er) Green Simpler Production Cathode Process EML (emissi e la er) W ite EML (emissi e la er) Red IL (interla er) HTL ( ole transportation la er) Lower Production Costs HIL ( ole in ection la er) HIL ( ole in ection la er) Anode (ITO) Anode (ITO) Glass substrate Glass substrate
PLED SMOLED
The challenges faced by both these approaches relates to the development of materials and manufacturing processes that give long life, reliability and – for illumination – the required performance as a source of white light.
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OLEDs
Small molecule OLEDs generally use rigid substrates with the organic layers being built up using a process called vacuum deposition. Flexible substrates are also possible. The layers are extremely thin and can be measured in nanometres. The active layers are carbon based organic compounds which are vulnerable to moisture and so they must be fully protected. An OLED, therefore, has a base (or substrate), then an anode (positive), a conductive layer, an emissive layer, a cathode (negative) and a protective layer on the top. Light is emitted when a voltage is applied across the anode /cathode, a property which is known as electroluminescence.
The vacuum deposition production process is well established in the electronics industry and has been used for many years. However it does influence both the cost and size of these OLEDs, which explains their initial commercial use in small screen displays, particularly in mobile phones. This application also demonstrates the fact that OLEDs can emit coloured light in high resolution; it is a self-illuminating display, not just a back light. They are also attractive to the portable device market because they are very thin, efficient and light in weight.
Light Output
Glass
Anode Hole Transport La er
Organic Emitters Electron Transport La er
Metal Cat ode V DC
OLED displays are controlled by either a passive or an active matrix, which is why they are referred to as PMOLED or AMOLED. In a PMOLED the anode and cathode layers are very fine strips laid perpendicularly to each other and the intersection points form the individual pixels that can be illuminated. In an AMOLED display the anode and cathode are full layers but a thin film transistor (TFT) array is placed below the anode, effectively integrating the switching electronics into the device. An AMOLED needs less power than a PMOLED.
In the display market OLEDs are, therefore, making significant inroads into the lighting market by replacing the backlit TFT / LCD technologies with self-illuminating screens. Large display screens using OLEDs are now available with screens sizes of around 55 inches currently being announced. Visual performance is very high with the benefit of very high contrast and deep blacks.
Some lighting manufacturers are beginning to market white OLEDs for specialised ‘designer’ lighting products, some of which might be considered closer to light sculptures, or art installations, rather than light fixtures. The makers of the few OLED lighting fixtures are, though, showing that this technology will offer new and interesting takes on the luminaire products. With an ultrathin, very light, light source the material required to make the fixture is reduced and there is often no need to provide any additional optics.
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PLEDs
In contrast to the small molecule OLEDs these devices use organic polymers to emit light through electroluminescence. A polymer is a material made up from large molecules and is most often associated with plastics; they may be naturally occurring or entirely man made materials. In PLEDS they are organic chemicals that are developed for their ability to emit the desired light.
One of the primary attractions of PLEDs is the potential for lower cost processing of the organic compounds as well as the ability to make larger panels. The organic compounds are soluble and their deposition in thin layers may be achieved by spinning or a continuous roll to roll printing process. PLEDs can use both rigid and flexible substrates but the latter approach is attractive to a mass production printing like process. However, the very thin layers required – virtually single molecule depth! – is extremely challenging. The layered structure is also simpler than that required by small molecule OLEDs; the active polymers serve a dual role in transmitting the charge and also converting it into light.
A PLED has 4 main layers:
1. A glass or plastic substrate - for PLED fabric displays, plastic tends to be a better choice because it’s less fragile but more flexible than glass. 2. A transparent electrode coating applied to one side of the substrate 3. The same side of the substrate is then coated with the light emitting polymer film 4. The final layer is an evaporated metal electrode, which is applied to the other side of the polymer film
PLEDs are a good example of ‘nanotechnology’. The total thickness of all layers in a PLED display device can be less than 500nm: a human hair is 0.1mm thick or over 200 times thicker.
OLEDs – Electrophosphorescence
The process of generating light from OLEDs is generally termed ‘electroluminescence’ or ‘electrofluorescence’. Both terms are broadly defined, in the context of OLEDs, as ‘the production of light through the application of a voltage to the organic semi-conductor layer’. They seem to be used as an interchangeable term when describing the OLED lighting process. In either case the term is used to describe the fundamental light generation process and effectively refers to the fact that while the voltage is applied, light is produced. However, in seeking higher quantum efficiencies from OLEDs, developers are confident that electrophosphorescence can be achieved in these devices.
The phenomenon ‘electrophosphorence’ in this context requires that the light emission persists after the voltage has been removed. Even though this may be a very short time it does mean that the quantum efficiency can be much higher. Making OLEDs do this requires special doping of the organic compounds, usually with a heavy metal.
83 www.thelia.org.uk Credit: Philips.
OLED properties and performance
OLEDs offer the prospect of very thin, large area, lighting panels with a soft, glare free output that can be mounted in any position. Current applications are restricted to opportunities where the practical maximum substrate size of 150mm x 150mm can be used. Most commercially available white OLEDs are <50cm2.
The control properties of OLEDs are similar to LEDs; they may be turned ON and OFF instantly, they can be dimmed readily and their life is not affected.
The current performance of OLEDs still lags behind LED sources as well as many conventional lamp technologies. In the laboratory, white OLED efficacies of over 100 lm/W have been achieved but practical values are around half this value. Improvements in efficacy are continuous and, using phosphorescent technology, the theoretical maximum is at least 200 lm/W. The major challenge to be overcome is useful life. While red and green OLEDs have been developed that have extremely long lives of well over 100,000 hours, blue OLEDs are struggling to achieve 20,000 hours. As a result the overall system life is restricted to the blue OLED lifespan if drastic colour shifts are to be avoided. Life for OLEDs is measured in a similar manner to that adopted for LEDs although the numbers quoted will be to L50 usually.
OLEDs are available commercially in white (various CCTs and CRIs), red, blue and green with a brightness of up to 4000 Cd/m2 although such performance is likely to be at the cost of its expected life.
The organic compounds used in OLEDs are prone to both oxidation and damage by water ingress. This means that they must be fully sealed and protected from physical damage if their rated life is not to be compromised.
OLEDs are an exciting technology that offers the prospect of entirely new ways to light interiors. Walls or ceiling that glow with soft light, integration into furniture and many other possibilities may be realised. It is even possible that future OLEDs, based on transparent substrates, might be incorporated into glazing so that a window by day becomes a light by night.
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ELECTRODELESS LAMPS Electrodeless lamps produce light without any physical electrical connections entering the glass or quartz envelope; in effect power is induced into the lamp to generate light. Broadly speaking this process can be demonstrated when holding an ordinary fluorescent lamp near to a high voltage distribution line making it glow. Nikola Tesla filed patents and designs in the late 19th Century describing this form of lighting!
This lamp technology, which is based on the excitation of gasses by electric / magnetic fields, is now produced in two forms. One is based on the low pressure mercury lamp (fluorescent) and is generally called induction lighting; the other uses a more intense light source (similar to an HID lamp) and is referred to as plasma lighting. Both have a long service life because they are not affected by the deterioration of electrodes that limits the life of more conventional light sources.
Induction lamps
Induction lamps are available as low pressure mercury lamps using the same tri-phosphor coating of the inner bulb surface and, as a result, their light quality and output are similar to conventional fluorescent lighting. They are available in two form factors, which are shown in the illustration below. The ‘bulb’ like form with an internal inductor is used for power ratings between 50 and 170 Watts. It is usually powered by electronic control gear that drives the inductor at a very high frequency, typically around 2.6MHz.
The alternative approach uses a closed tube construction (see illustration above) variously shaped as oval, rectangular or circular. Two coils are attached to the continuous tube and high frequency current applied (typically 100-300 KHz). These lamps are often referred to as magnetic induction lamps and have an external ballast to drive the coils, or external inductors.
There are smaller induction lamps, in the range 20W – 150W, that have an integral ballast but these are generally less efficient and have shorter service lives.
In all types of induction lighting the enclosed mercury vapour becomes excited and radiates UV, which is then converted to visible light by the phosphor coating. The electrodeless design allows the manufacturer to use phosphors that are normally harmful to conventional fluorescent lamps, and lamps are available with CCTs from 2700K – 6500K and CRI (Ra) >80. The large surface area of the lamp generates a softer light and system efficacies between 40lm/W and >80lm/W are offered depending on the form factor, quality and power rating of the product.
Power ratings for induction lamps from different manufacturers, covering all form factors, range between 20W and 500W. Their service life varies somewhat; generally they fall in the range 60,000 – 100,000 hours, but some integrated models may be as low as 15,000 hours. Induction lamps switch ON instantly from either cold or hot conditions, although they usually require a run-up period to full brightness. The lamps are dimmable although some are limited to 50% + only.
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Advantages
The primary advantage of induction lamps has been their comparatively long life, which means that they are virtually maintenance free. This characteristic has made them popular for use in difficult to access locations where high quality, soft white light is required. As a lamp, they are also replaceable.
Disadvantages
The manufacturers of induction lamps have not followed any specific standards in shapes and forms, which means that there a large number of variations available. Add to this their specialised nature and the result is a generally high unit cost that has discouraged wider adoption. The cost issue is further complicated by the need for very high quality electronic ballasts to match the lamp life and avoid problems with EMC compliance.
Applications
Difficult to access locations in high bay, low Bay, road tunnels, mast lighting, street lamps and downlighters in high ceilings.
Performance
Typical Lumen spread; (L) 1,000 to 45,000
Typical Wattage spread; (W) 20 to 400
Life claims; (H) 50,000 to 100,000 (integrated types from 15,000)
Lumen/Watt (lm/W) up to 85
CCT: (K) 2700 to 6500
Colour rendering index; (Ra) >=80, with high consistency through life
Lumen maintenance In line with existing phosphor performance
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Plasma Lamps
High efficiency plasma (HEP) lighting belongs to a class of electrodeless high intensity discharge (EHID) lamps, characterised by the use of high frequency (radio-frequency (RF) or microwave (µw)) power to ignite and maintain the lamp discharge. As in conventional metal halide HID lamps, the light source generally operates at a few atmospheres gas pressure; typically the radiation is produced from metal atoms and metal halide molecules, introduced in the lamp in the form of metal halide salts, although other molecular radiators, such as sulphur (see below), may be used.
The cavity, (diagram below), is the system component that constrains and focuses the radio frequency or microwave energy on to the lamp capsule. The energy is then transferred to the gas and dose in the lamp capsule. The size of the cavity is primarily dictated by its dielectric constant: air cavities are larger than fused silica cavities, which in turn are larger than ceramic cavities. Typical system component arrangement:
Ca it AC DC HF Dri er Wa e Guide Lamp Power Suppl
HEP lamps offer an intense, compact light source with a high lumen package and can have a very good spectral power distribution and a CRI of up to 95. They also demonstrate good cyclability although the switch ON is not instantaneous; the lack of electrodes removes one of the limiting factors affecting lamp life. Claimed efficacy ranges from 85 lm/W – 150 lm/W. Lamp life to L70 can be up to 50,000 hours.
Representative Spectral Power Distribution LEP Source
Relative Energy
Wavelength (nm)
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Advantages
Plasma light sources can be made smaller than conventional HID lamps by the selection of the appropriate combination of geometry and material for the resonant cavity. Ceramic cavities, although smaller than for fused silica, limit the light output to the optically transparent part of the lamps. On the other hand, fused silica cavities are optically transparent throughout.
Absence of electrodes, which limit lamp life and the dose materials that can be used, lead to longer lamp life, as well as greatly improved lamp lumen maintenance factors (LLMF) when compared to conventional metal halide discharge types. Greater options in dose potential, including mercury free, expand possibilities in terms of lumens, CCT and Ra.
Plasma lighting systems are intrinsically designed for dimming.
Disadvantages
Different manufacturers have pursued different variations on the Plasma theme. Consequently, there are various different types of lamps available. Their speciality currently limits their availability and distribution.
Where plasma lamps use microwave power the frequency used is 2.45 GHz and great care must be taken to avoid interference with other users near to this bandwidth.
Applications
The application range for plasma based sources covers: high bay, roadway, tunnels, high mast, area, entertainment, architectural, UV generation and, in particular, horticultural lighting.
Performance
Because of the nature of the products, these lamps are typically supplied with luminaires. However lamp modules can be replaced if required, but this means that actual performance data is often quoted per luminaire rather than the normal lamp data. Restrictions on burn angle may apply and, in addition, the luminaire design needs to incorporate the safety features usually associated with the use of normal HID lamps. Viz: containment through end-of-lamp failure (explosion) and protection from harmful UV where exposed silica bodied lamps and resonance cavity are employed.
Typical Lumen spread; (L) 17,000 to 98,000L
Typical Wattage spread; (W) 160 to 1030W
Life claims; (H) 20,000 to 50,000
Lumen/Watt (lm/W) Typically 85 - 95
CCT: (K) 3500 to 8300
Colour rendering index; (Ra) 75 to 95
Lumen maintenance 70% @ life to 95% @ life
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Sulphur lamps
A variation of the plasma lamp that uses sulphur compounds rather than metal halides, these are highly specialised and unusual. The lamp capsule in some products needs to be constantly rotated to produce an even light source and most products are high wattage / high lumen packages. The lamp is claimed to have a very long life – up to 99,000 hours – although the magnetron powering it may only be rated at 40,000 hours! Sulphur lamps produce white light with a CRI between 80 and 96 although there is a noticeable greenish tinge due to the compounds used in the capsule.
Sulphur lamps are offered in power ratings from 700W to 1400W and an efficacy of between 54lm/W and 100 lm/W. Their intense light output together with the somewhat unusual mechanical and electrical requirements often leads to them being used with light pipes and similar optical distribution methods.
Laser lighting
Developers are exploring the potential use of laser diodes to produce white light that can be used in general illumination applications. The research is focussed on blue and near ultraviolet laser diodes exciting suitable phosphors. Early laboratory results have confirmed the feasibility but efficacy is not yet comparable to the performance of white LEDs. Experiments have produced light sources up to 250 lumens but these do not have a good CRI (<60) but reached 78 lm/W. Using the near UV laser with RGB phosphors did achieve a high CRI (>90) but only offered an efficacy of 19 lm/W.
The laboratory work has clearly shown that laser lighting is feasible but it is very much an emerging technology. At least one car manufacturer is working on this technology with the expectation that it might be a route to improved headlamps.
In the meantime laser lighting is most likely to be seen in art and entertainment creating fast moving displays and effects, often using green emitting sources.
Electron stimulated lighting
A ‘niche’ lamp manufactured in the US to satisfy the demand for a more efficient R30 lamp uses technology based on the cathode ray tube. The technology is called Electron Stimulated Luminescence™ (ESL) by its maker and it produces a soft white light with a claimed CRI in excess of 90Ra. The colour temperature is 3200K and it produces about 500 lumens from a power consumption of 19.5 Watts. Life is claimed as ‘approximately 11,000 hours’ for this lamp, but this figure is not qualified in any way. The actual lamp is similar to a CFLi in appearance because it contains its own electronic control gear. One advantage compared to CFL technology is the absence of any mercury while another is the fact that it can be dimmed by typical triac based household dimmers.
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LAMPS AND THE ENVIRONMENT
Atmospheric pollution
Every kWh of electrical energy saved prevents the release of 0.7kg of carbon dioxide into the atmosphere. In addition, there are reduced emissions of gases such as sulphur and nitrogen oxides which contribute to ‘acid rain’. The saving of 7 TWh of electrical energy per year corresponds to a reduction in mercury emissions from power stations, as a result of burning less fossil fuel, of approximately 200kg per year. This is over 3 times the amount of mercury contained in the energy efficient light sources used.
Sky-glow pollution
Skyward light wastes energy and affects astronomical observations and appreciation of the night sky. LIA leads the call for luminaires and lighting installations that make good use of the output of lamps, and put light where it is required. For roadway lighting, less obtrusive light can be achieved by using high pressure sodium lamps in place of low pressure sodium lamps. This is due to the better optical control possible from the more compact arc tube.
Material use efficiency
Over the years, lamp manufacturers have been able to progressively reduce the amount of materials used and also increase the service lives of lamps. This reduces the requirement for the non- renewable materials used in lamp construction. In the case of tungsten, the introduction of long-life CFLs has reduced the requirement for tungsten filaments for short-life GLS lamps.
Packaging
LIA lamp manufacturers design product packaging which minimises the use of materials consistent with protection of the product and safe handling. Recycled packaging materials are used in packaging design whenever possible. This is an important part of CE Marking and the Ecolabel scheme.
Material sensitive to the environment
The element of principal public concern is mercury, an essential constituent of most discharge lamps. Lamp manufacturers have progressively reduced the quantity of mercury in fluorescent lamps, and a 90% reduction in quantity has been achieved over the last 20 years. Cadmium was eliminated from fluorescent lamps in the early 1980s.
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FAQS
Here are brief answers to some of the more common questions asked about lamps:
Q. Is a GLS lamp life affected by switching rate? A. Life is tested with one switching per 12 hours. One switching per hour reduces life about 1%.
Q. What is the effect of switching frequency on the electrical life of linear fluorescent lamps? A. A guide to this effect is shown in Fig 6, p.24. With electronic circuits those including preheating will extend lamp life but those with ‘cold start will not.
Q. Is there high energy consumption at switch-on of fluorescent and discharge lamps? A. The energy taken during starting is a small fraction of the energy taken during one minute’s operation. Current taken is usually higher than during operation. There can be a high transient current where capacitors are across the supply.
Q. Should tungsten halogen lamps be dimmed? A. Life will not usually be affected, but the extra efficacy of the halogen lamp will be lost during dimming. If lamps are rarely operated at full light output, blackening can develop earlier than usual, and could be unacceptable. Blackening can be removed by operating the lamps at full power for a short period.
Q. Will high pressure discharge lamps go out if the supply voltage drops? A. A transient drop may put out the lamp, which must then cool before restarting. A slow decline in supply voltage (say down to 85%) can usually be tolerated. There are twin arc tube lamp types and hot restrike ignitor systems that can minimise ‘lamp out’ time. Modern electronic circuits can compensate for variations in supply voltage and supply constant lamp operating conditions.
Q. Should ‘energy limiters’ (supply voltage reducers) be used? A. Lamp life, starting, and operation may be impaired. Lamp replacement arrangements may be annulled. In some instances these devices can render equipment unsafe. LIA strongly recommends that energy should not be saved by reducing lighting levels, but by the selection of more efficient lamps and equipment, or by engineered regulation of output.
Q. Is there a high level of UV from unenclosed tungsten, fluorescent or discharge lamps? A. Even at 1000 lux, UV levels are lower than outside on an average day. Observe any special instructions supplied with these lamps. Lamp standards have been amended to include maximum allowable UV output of relevant lamps and UV block lamp types have been developed. Special consideration should be given to display situations where delicate materials are exposed to high lighting levels e.g. retail clothing displays or museums and art galleries.
Q. Why replace existing T12 tubes with triphosphor T8 lamps rather than the less expensive halophosphate T8 versions? A. Although both will provide approximately 10% energy saving, the triphosphor tube will give about 12% more light and greatly improved colour rendition. Combined with excellent lumen maintenance, the service life of the triphosphor tubes can be almost twice that of the halophosphate tubes, virtually halving annual lamp replacement and maintenance costs, which will more than offset the extra cost of the triphosphor tubes.
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Q. Why do T5 tubes give their maximum light output at 35°C instead of the normal 25°C for other fluorescent tubes? A. Because the ambient temperature in the new smaller enclosed T5 luminaires is closer to 35°C. If the maximum light output was at 25°C it would be necessary to design larger luminaires and not exploit the opportunities offered by the physical reduction of T5 tubes.
Q. What are amalgam CFLs and what are their advantages? A. The lamps use an alloy of mercury instead of pure mercury. The amalgam enables a relatively constant mercury vapour pressure over a wide temperature range and thus maximum light output. This offers flexibility in luminaire design and acceptable environmental conditions. Amalgam CFLs emit 90% or more lumens in 5°C to 65°C ambient temperatures. Mercury CFLs only emit 90% or more lumens in 20°C to 45°C ambient temperatures.
Q. Can T12 tubes be operated on high frequency ballasts? A. It is possible to operate some T12 tubes on HF ballasts designed for T8 lamps. However this is not recommended as the T12 lamps will only operate at a reduced light output.
Q. Why do metal halide lamps shift in colour in use and can it be prevented? A. Low supply voltage or incorrect ballast tapping can under power the lamp and produce a noticeable colour shift. Also there is a slow diffusion by some of the metals through the quartz arc tube, changing the metallic mixture and hence the colour of the lamp. This problem has been overcome by making arc tube from polycrystalline alumina which prevent diffusion losses and ensures colours stability throughout life.
Q. Do energy saving light bulbs (CFLis) fit in ordinary light fittings? A. Energy saving light bulbs (CFLis) fit in ordinary light fittings - and if you have a dimmer switch you can buy special dimming energy saving light bulbs bulbs.
Q. How much do energy saving light bulbs cost? A. At the moment, energy saving light bulbs are a little more expensive than the old tungsten filament light bulbs, typically costing around £2 - but you’ll easily make back the difference on your electricity bill in about a year. Energy saving light bulbs will become even cheaper as more are produced, because manufacturers will be able to make them more efficiently.
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GLOSSARY
Amperes Candlepower (“Amps.”) A measure of electrical current. In incandescent Luminous intensity expressed in candelas. Plots of lamps, the current is related to voltage and power as luminous intensity, called candlepower distribution curves, follows: Current (Amps) = Power (Watts) / Voltage (Volts). are used to indicate the intensity distribution characteristics of reflector-type lamps. A measure of intensity American National Standards Institute (ANSI) mathematically related to lumens. Candlepower is often to A consensus organisation which coordinates voluntary measure the intensity of lamps that project light. standards for the physical, electrical and performance characteristics of lamps, ballasts, luminaries and other Chromaticity (CCT) lighting and electrical equipment. Also called Correlated Colour Temperature (CCT). Chromaticity tells you what the lamp itself or a neutral Ballast surface illuminated by a lamp will look like. Chromaticity An auxiliary piece of equipment designed to start and to sets the “tone” or atmosphere of a room: warm, cool or properly control the flow of power to gas discharge light something in between. Chromaticity is usually measured in sources such as fluorescent and high intensity discharge Kelvins. It can also be defined by using x and y coordinated (HID) lamps. against a standard chromaticity scale developed by the International Commission on Illumination (CIE). Beam Angle The angular dimension of the cone of light from reflector Correlated Colour Temperature (CCT) lamps, encompassing the central part of the beam out Also called Chromaticity. CCT tells you what the lamp to the angle where the intensity is 50% of maximum. The itself or a neutral surface illuminated by a lamp will look beam angle sometimes called “beam spread”, is often part like. CCT sets the “tone” or atmosphere of a room: warm, of the ordering code for reflector lamps. cool or something in between. CCT is usually measured in Kelvins. It can also be defined by using x and y coordinated British Standard (BS) against a standard chromaticity scale developed by the British Standards are produced by BSI British Standards, International Commission on Illumination (CIE). a division of BSI Group that is incorporated under a Royal Charter and is formally designated as the National Colour Rendering Index (CRI) Standards Body (NSB) for the UK. An international system used to rate a lamp’s ability to render object colours. The higher the CRI (based upon Candela (cd) a 0-100 scale), the better colours appear, CRI ratings The international unit (SI) of luminous intensity. The term of various lamps may be compared, but a numerical has been retained from the early days of lighting when a comparison is only valid if the lamps are also rated for the standard candle of a fixed size and composition was used same chromaticity or colour temperature. A measurement as a basis for evaluating the intensity of other light sources. of the colour shift an object undergoes when illuminated by Sometimes the term “candle power” is used to describe the the light source, as compared to a reference source at the relative intensity of a source. same colour temperature. Colour rendering is measured on an index from 0-100, with natural daylight equal to 100. candela Colour Temperature Originally, a term used to describe the “whiteness” of candela incandescent lamp light. Colour temperature is directly related to the physical temperature of the filament in S uare oot incandescent lamps so the Kelvin (absolute) temperature oot scale is used to describe colour temperature. For discharge lamps where no hot filament is involved, candela the term “correlated colour temperature” is used to indicate that the light appears as if the discharge lamp is operating at a given colour temperature. More recently, candela the term “chromaticity” has been used in place of colour temperature. Chromaticity” has been used in place of candela
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colour temperature. Typical colour temperatures are European Committee for Electrotechnical 2800K (incandescent), 3000K (halogen), 4100K (cool Standardisation (CENELEC) white or SP41 fluorescent), and 5000K (daylight-simulating CENELEC is a non-profit technical organization composed fluorescent colours. of the National Electrotechnical Committees of 30 European countries. In addition, 8 National Committees Compact Fluorescent Lamp (CFL) from neighbouring countries are participating in CENELEC The general term applied to families of smaller diameter work with an Affiliate status. CENELEC’s mission is to fluorescent lamps, some of which have built in ballasts prepare voluntary electrotechnical standards that help and bayonet or screw-in bases for easy replacement of develop the Single European Market/European Economic incandescent lamps, others utilise a remote ballast in the Area for electrical and electronic goods and services same format as a linear fluorescent lamp. removing barriers to trade, creating new markets and Compact Fluorescent Lamp integrated (CFLi) cutting compliance costs. The general term applied to families of smaller diameter European Committee for Standardisation (CEN) fluorescent lamps which have built in ballasts and bayonet/ The European Committee for Standardization (CEN) is screw-in/pin-ended bases for easy replacement of a business facilitator in Europe, removing trade barriers incandescent and halogen lamps. for European industry and consumers. Its mission is to Compact Fluorescent Lamp non-integrated (CFLni) foster the European economy in global trading, the welfare of European citizens and the environment. Through its The general term applied to families of smaller diameter services it provides a platform for the development of fluorescent lamps with curved glass tubes which operate European Standards and other technical specifications. by means of a remote ballasts and in some cases, an ignitor. Euro Norm (EN) Efficacy CEN’s 30 National Members work together to develop voluntary European Standards (ENs). These standards Efficacy is the rate at which a lamp is able to convert have a unique status, since they also are national standards electrical power (Watts) into light (Lumens), expressed in each of its 30 Member countries. With one common in terms of lumens per watt (Lm/W). Put simply, a watt or standard in all these countries, and every conflicting electricity is the amount of power in and a lumen or light is national standard withdrawn, a product can reach a far the amount of power out. Efficacy is a critical consideration wider market with much lower development and testing when evaluating a lamp because lighting represents 30 to costs. ENs help build a European Internal Market for goods 50% of the total operating cost of a typical installation and and services and to position Europe in the global economy. can affect related costs such as air conditioning. Secondly, Standards issued by CEN/CENELEC are normally prefixed energy accounts for 86% of the cost of an average lighting by the national issuing body e.g. BS EN investment (maintenance accounts for 11%; the lighting itself, 3%) and has a major impact on operating costs. Fluorescent Lamp And finally, a lighting system that uses energy efficiently is A high efficiency lamp utilizing an electric discharge beneficial to the environment. through low pressure mercury vapour to produce ultraviolet Electromagnetic Spectrum (UV) energy. The UV excites phosphor materials applied as a thin layer on the inside of a glass tube which makes up A continuum of electric and magnetic radiation that can the structure of the lamp. The phosphors transform the UV be characterized by wavelength or frequency. Visible light to visible light. encompasses a small part of the electromagnetic spectrum in the region from about 380 nanometres (violet) to 770 Halogen Lamp nanometres (red) by wavelength. A short name for the tungsten-halogen lamp. Halogen Electronic Ballast lamps are high pressure incandescent lamps containing halogen gases such as iodine or bromine which allow A short name for a fluorescent high frequency electronic the filaments to be operated at higher temperatures ballast. Electronic ballasts use solid state electronic and higher efficacies. At high-temperatures, chemical components and typically operate fluorescent lamps at reaction involving tungsten and the halogen gas recycles frequencies in the range of 25-35 kHz. The benefits are: evaporated particles of tungsten back onto the increased lamp efficacy, reduced ballast losses and lighter, filament surface. smaller ballasts compared to electromagnetic ballasts. Electronic ballasts may also be used with HID lamps, but the circuits are quite different, there are few designs at present and only minor lamp efficacy improvements result.
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High-Intensity Discharge (HID) Lamp Lamp A general term for mercury, metal halide and high-pressure The term used to refer to the complete light source sodium lamps. HID lamps contain compact arc tubes package including the inner parts as well as the outer bulb which enclose various gases and metal salts operating or tube. “Lamp”, of course, is also commonly used to refer at relatively high pressures and temperatures. to a type of small light fixtures such as a table lamp.
Illuminance (lx) Light Emitting Diode (LED) The “density” of light (lumens/area) incident on a surface. An LED or light-emitting diode is a small semiconductor Illuminance is measured in lumens/metre2 or lux. device which emits light, usually coloured, when an electric current passes through it. LEDs are energy saving and “MsoNormal”>Incandescent Lamp > have a long service life.
A light source which generates light utilizing a thin filament Light wire (usually of tungsten) heated to white heat by an Radiant energy which can be sensed or seen by the human electric current passing through it. eye. Visible light is measured in lumens. The term generally Infrared radiation (IR) applied to the visible energy from a source. Light is usually measured in lumens or candlepower. When light strikes Electromagnetic energy radiated in the wavelength range a surface, it is either absorbed, reflected or transmitted. of about 770 to 1106 nanometres. Energy in this range Light is said to travel in straight lines. cannot be seen by the human eye, but can be sensed as heat by the skin. Light Output Ratio (LOR) Instant Start The ratio between the light output of the lamp and the luminaire. LOR = Luminaire Output / Lamp Output A type of fluorescent lamp-ballast circuit designed to in Lumens start fluorescent lamps as soon as the power is applied. Originally, instant-start circuits were developed to eliminate Lumens (lm) separate mechanical starter devices. Slimline fluorescent The basic unit of measurement for light. Luminous lamps operate only on instant start circuits. flux describes the total quantity of light emitted by a International Organisation for Standardisation (ISO) light source, both visible and non-visible. The unit of measurement is Lumens (lm). Typically used for measuring ISO (International Organization for Standardization) is the non-reflector lamps such as linear fluorescent, compact world’s largest developer and publisher of International fluorescent, HiD, Halogen capsules and LEDs. Standards. ISO is a network of the national standards institutes of 159 countries, one member per country, with a Lux (lx) Central Secretariat in Geneva, Switzerland, that coordinates The SI (International System) unit of illumination: one lumen the system. ISO is a non-governmental organization that uniformly distributed over an area of one square meter. forms a bridge between the public and private sectors. On the one hand, many of its member institutes are part of the Organic Light Emitting Diode (OLED) governmental structure of their countries, or are mandated A Large area light source, where electrical energy is by their government. On the other hand, other members converted into light energy within a solid state environment have their roots uniquely in the private sector, having been (not gas or liquid). Devices constructed with low set up by national partnerships of industry associations. molecular weight organic molecules deposited by thermal Therefore, ISO enables a consensus to be reached on evaporation, sandwiched between two metallic electrodes. solutions that meet both the requirements of business Typically up to 16 organic layers are sandwiched between and the broader needs of society. the electrodes. When driven at low DC voltages these Kilowatt (Kw) devices emit light across the visible spectrum, including white. Presently made on glass substrates but much A measure of electrical power equal to 1000 watts. research being conducted on suitable flexible plastic Kilowatt Hour (kWh) substrates. The standard measure of electrical energy and the typical billing unit used by electrical utilities for electricity use. A 100-watt lamp operated for 10 hours consumes 1000 watt- hours (100 x 10) or 1 kilowatt-hour. If the energy company charge £0.10/kWh, then the electricity cost for the 10 hours of operation would be 10 pence (1 x £0.10).
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Parabolic Aluminized Reflector (PAR) Transformer A type of reflector lamp, either incandescent or halogen. Transformers reduce the line voltage (for instance 230 V) to the lower voltage required for operating low-voltage Polymer Light Emitting Diode (PLED) halogen lamps. This will generally be 12 V. A Large emissive area light source, where electrical energy is converted into light energy within a solid state Voltage (V) environment (not gas or liquid). Devices constructed with A measurement of the electromotive force in an electrical high molecular weight polymers which are deposited by circuit or device expressed in volts. Voltage can be thought printing methods at atmospheric pressure, in a clean-room of as being analogous to the pressure in a waterline. environment. Typically only 3 organic layers are required for the emission of white light. A single polymer which emits Watt (W) white light is key to this technology. These sources emit no A unit of electrical power. Lamps are rated in watts to UV or IR energy. indicate their power consumption. Power consumed over time equals the electrical energy used. Printed Circuit Board (PCB) A Printed Circuit Board (PCB) would typically be used to Ultraviolet (UV) mount LEDs or within electronic of ballasts and integrated Radiant energy in the range of about 100-380 nanometre Compact Fluorescent Lamps (CFLs) (NM). Light that is shorter in wavelength and higher in frequency than visible violet light. Solid State Lighting (SSL) The term Solid State Lighting (SSL) is typically used to describe LED lighting where the light is created on a solid state PCB.
Common cap lamp types (drawings not to scale) mm mm
mm mm mm mm mm E14 E27 E40 B15d GX16d S14s S14d
mm mm mm . mm mm mm mm mm B22d Fa4 R7s G4 G9 G53 GY6.35 GY4
mm mm mm . mm . mm GU4 GX5.3 GU5.3 GU10 GZ10
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Lighting standards lighting applications
There are a considerable number of EU Directives, Standards and Guides which are influencing the development of the lighting market. Manufacturers and Stakeholders need to invest in their development and monitoring. These influencing factors provide opportunities for market exploitation and drive growth and business opportunities. LIA members and staff participate in the drafting and revision of International, European and British Standards and participate in schemes for independent assurance of quality. The LIA can provide full details of the standards - for more information and costs, please contact Sarah Lavell [email protected]
In many instances modern lighting product standards and revisions are drafted by the International Electrotechnical Commission (IEC) and parallel-voted both internationally and in Europe (CENELEC). This has accelerated the process of publishing new standards and revising/updating existing standards. This has allowed BSI standards to also have enhanced publication/revision capability and the adoption by IEC of the 5 digit standard number used by CENELEC has simplified the cross referencing of relevant international, regional and national standards.
Organisations
The following table highlights the key organizations and their authority/responsibility:
General Electrical Lighting (applications) (products) (applications) World bodies ISO IEC CIE
European bodies CEN CENELEC LuxEuropa
National bodies Standards Institutes - Learned Society
Note 1: World standards are offered for voluntary for adoption by member Note 2: Member national standards institutes must publish all CEN and CENELEC standards and remove any conflicting national standard
CEN Lighting Application Standards
CEN Standards Covers Impact on practice
EN 12464-1 Indoor Workplace Use three E levels, High RA, UGR, VDU
EN 12464-2 Outdoor Workplace Use two levels, ULR, GR, Ra, Uo
EN 12193 Sport Covers most indoor and outdoor sports and data needs
EN 1838 Emergency Lighting Escape routes, open areas, high risk areas, signs
EN 13032-1 Photometry and Data More stringent tests and data, practice and claims
EN 13032-2 Photometry for Workplace Data presentation and use
EN 13032-3 Photometry for Emergency Data presentation and use
EN 13201-1/4 Road Lighting practice New critera, data, calculations and verification procedure
EN 50172 Emergency lighting system Defines testing and inspection of systems
EN 15193 EPB lighting requirement Gives procedure for estimating energy requirements (LENI for lighting schools
EN 14255 Limit radiation ecposure Restrict non-visible radiation emissions
EN 13032-4 Photometry for LED Data presentation and use
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CIE guides - these supplement the standards
CIE 97.2 Maintenance of indoor electric lighting systems CIE 99 Lighting education CIE 103 Technical collection, industry, economics, colour, erythema, economics of interior lighting maintenance CIE 106 Collection UV impact - photobiology, photochemistry, lighting for plants CIE 117 Discomfort glare in interior lighting - UGR CIE 139 Collection of SAD effects CIE 150 Obtrusive light CIE 154 Maintenance of outdoor electric lighting systems
There are also CIE guides on indoor, roads, tunnels, sports, etc. lighting needs
EU Directives relevant to lighting
There are numerous European Union Laws which impact on the UK lighting market. But how are they implemented? They are:
• Created by European Parliament and Council • Effective date published in the Official Journal of the European Union • Time set for transposition/adoption by Member States • Type Article 95 - to be implemented without any deviation • Type Article 175 - permits some country interpretations or deviations • Type Article 14 - Route for initiating reviews, updates or changes • The Member States must embody in its Laws as Acts or Regulations • Close surveillance/policing is by Member State authorities/agencies
Key EU Directives and their Abbreviations
The following table details the key EU Standards and their Abbreviations.
CE mark A mark that acts as a passport for the product to place on to EU market demands mark and conformity to all relevant directives (these are not listed) manufacturer self declaration of conformity (except medical and gas appliances that require 3rd party certification) LVD Low Voltage directive for selling safe products demands proof on electrical safety, can be satisfied by tests to EN 60598 updating under consideration but resisted by lobby groups GPSD General Product Safety directive for products in service demands life test and information (up to 10 years liability) EMC ElectroMagnetic Compatibility directive for limiting electrical and magnetic interference and adequate capacity for immunity(rejection) demands conduction, emitting (E and M) and immunity testing CPD Construction Product directive safety in building/services design and build applies to first fix products, emergency lighting WEEE Waste Electrical and Electronic Equipment directive. Place crossed-out wheeled bin symbol on product to show new waste. Producer responsibility for end of life collection, treatment, recycling, disposal, financing of product. RoHS Restriction of Hazardous Substances directive Limits or bans the amount of hazardous substance used in products. Producer responsible to measure and calculate the weight ratio. Require registration for handling excess amounts BaA Battery and Accumulator directive. Restricts the use and disposal of cadmium and lead cell devices. Require licensed end of life collection and rehandling EELP Energy Efficiency Labelling of Product directive Add energy class label to product (fluorescent lamp and ballast) EPB Energy Efficiency Labelling of Product directive Add energy class label to product (fluorescent lamp and ballast) ErP Ecodesign of Energy related Products directive. Aim to reduce the consumption of natural resources and energy and minimise environmental impacts of products across the whole of their life cycle. Practice ecodesign, give instruction on use, limit stand-by devices. Assessment of impact and supporting standards in progress RED Radio Equipment Directive covering lamps with built-in radio communication (e.g. wifi, Bluetooth etc)
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KEY LAMP STANDARDS
Tungsten Filament Lamps
• BS EN 60432-1: Safety specification for incandescent lamps. Tungsten filament lamps for domestic and similar general lighting purposes. • BS EN 60432-2: Incandescent lamps. Safety specifications. Tungsten halogen lamps for domestic and similar general lighting purposes • BS EN 60432-3: Incandescent lamps. Safety specifications. Tungsten-halogen lamps (non-vehicle) • BS EN 60064: Tungsten filament lamps for domestic and similar general lighting purposes - Performance requirements • BS EN 60357: Tungsten halogen lamps (non-vehicle) - Performance specifications • BS EN 50285: Energy efficiency of electric lamps for household use – Measurement Methods
Vehicle Lamps
• BS EN 60809: Lamps for road vehicles. Dimensional, electrical and luminous requirements • BS EN 60810: Lamps for road vehicles. Performance requirements
Double Capped Fluorescent Lamps
• BS EN 61195: Double-capped fluorescent lamps. Safety specifications • BS EN 60081 : Double-capped fluorescent lamps - Performance specifications
Single Capped Fluorescent Lamps
• BS EN 61199: Single-capped fluorescent lamps. Safety specifications • BS EN 60901: Single-capped fluorescent lamps – Performance specifications
Self Ballasted Lamps
• BS EN 60968: Specification for self-ballasted lamps for general lighting services. Safety requirements • BS EN 60969 : Self-ballasted lamps for general lighting services – Performance requirements
High Intensity Discharge Lamps
• BS EN 62035: Discharge lamps (excluding fluorescent lamps). Safety specifications • BS EN 60188: High-pressure mercury vapour lamps. Performance specifications • BS EN 60192: Low pressure sodium vapour lamps. Performance specification • BS EN 60662: Specification for high-pressure sodium vapour lamps • BS EN 61167: Specification for metal halide lamps
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LED
• BS EN 62612: Self-ballasted LED lamps for general lighting services > 50 V - Performance requirements • BS EN 62717: LED Modules for General Lighting - Performance requirements • BS EN 62560Self-ballasted LED-lamps for general lighting services > 50 V - Safety specifications • BS EN 62838LEDsi lamps for general lighting services with supply voltages not exceeding 50 V a.c. r.m.s. or 120 V ripple free d.c. - Safety specifications • BS EN 62776Double-capped LED lamps for general lighting services – Safety specifications • BS EN 62031LED Modules for General Lighting – Safety Specifications
Others
• BS EN 60061 series: Lamp caps and holders together with gauges for the control of interchangeability and safety • BS EN 61341: Method of measurement of centre beam intensity and beam angle(s) of reflector lamps • BS EN 61231: International lamp coding system (ILCOS) • BS EN 62471: Photobiological safety of lamps and lamp systems • BS EN 62778 : Application of IEC 62471 to light sources and luminaires for the assessment of blue light hazard • BS EN 62504 : General lighting - Light emitting diode (LED) products and related equipment - Terms and definitions
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Summary of Lamp Characteristics
Lamp Output Power Efficiency Control Colour Colour Run Up Life Name Range (lm) Range (w) (lmw) Gear Temp (K) Rendering (Ra) Time Dimming (hrs)1 Comments
Incandescent Large variety GLS 5-12,000 1-2000 8-14 No 2500-2700 100 Instant Easy to 0% 1,000 of shapes and sizes of lamps
TH 40-50,000 Apr 00 15-25 No2 2700-3200 1003 Instant Easy to 0% 1500-5000 -
Fluorescent
There are some higher power lamps T124 1000-10,500 25-140 50-80 Yes 3000-6500 50-90 30 sec Limited to 25% 8000-12,000 available for special applications such as cold stores
T8 650-6200 13-70 50-96 Yes 2700-17000 50-98 30 sec Easy to 2% 8000-17,000 -
T5 120-8550 6-120 20-935 Yes 2700-17000 82-95 30 sec Easy to 2% 8000-19,000 -
Compact (CFL) ------
CFL Some types Up to (Non intergral 250-9000 8-120 30-70 Yes 2700-6500 85-90 15-90 Sec - to 5% 15,000 control gear) CFL Some types (Intergral 100-1500 5-30 20-50 No 2700 >80 60 Sec 5000-15,000 - to 20% control gear) High Pressure Mercury
MBF/HPL 2000-58,500 60-1040 33-57 Yes 3200-3900 40-50 4 min No 8000-10,000 -
Metal Halide Lamps
Quartz tube 5200-200,000 85-2050 60-90 Yes 3000-6000 60-90 1-8 min No 2000-7000
The lamp range is Ceramic tube 1600-26,000 20-250 65-97 Yes 3000-4400 78-93 2 min Limited6 6000-10,000 increasing rapidly
Low Pressure Sodium
Good lumen maintenance, but SOX SOX-E 1800-32,00 26-200 70-180 Yes N/A N/A 10-20 min No 15,000-20,000 power consumption goes up through life
High Pressure Sodium
SON 4300-130,000 85-1040 53-142 Yes 1900-2100 19-25 3-7 min Limited to 25% 10,000-20,000 -
Delux SON 12,500-37,000 165-430 75-86 Yes 2150 65 5 min Limited to 25% 10,000-14,000 -
White SON 1800-5000 45-115 40-44 Yes 2500 83 2 min No 6000-9000 -
Induction
- 2600-12,000 55-165 47-80 Yes 2550-4000 80 1 min No 60,000+ -
LED
15,000- The LEDs range is - 30-3000 1-30 50-150 Yes 2685-6500 40-85 Instant Easy to 0% 60,000 increasing rapidly
1 Economic lamp life may be limited by lumen depreciation 2 A lot of TH types are designed to run on low voltages and thus need a transformer or other device to supply the necessary voltage 3 Some lamps with dichroic reflectors have part of the red end of the spectrum missing and thus do not have a colour rendering index of 100. Information from lamp manufacturer. 4 T12 lamps are not generally used in new installations as T5 & T8 types are more efficient 5 Most T5 lamps are optimised to give maximum light output at 350C. The figures in this table are based upon their output at 25 degrees C. As in most luminaires the lamp runs hotter so will operate nearer the optimum temperature. 6 Most manufacturers are working on dimming control gear for this sort of lamp, but most products released onto the market so far have had major problems.
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Useful Links
BSI (British Standards Institute) BIS (Departmaent for Business Innovation & Skills) Carbon Trust DEFRA (Department for Environment, Food and Rural Affairs) EST (Energy Saving Trust) ECA (Enhanced Capital Allowances) EUR-Lex (European Union Law) Europa (Gateway to the European Union) Lamptech Recolight BEIS (Department for Business, Energy & Industrial Strategy) LightingEurope
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