Outer Ring Road, Bellandur, Bengaluru – 560103
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
EEE84 Project- Phase II
Report on AUTOMATIC POWER FACTOR CORRECTION
Submitted in the partial fulfilment of the Final Year Project - Phase II Submitted by
KARTHIK K 1NH16EE063
ANIL TIKOTI 1NH17EE403
SHUBHAM MISHRA 1NH17EE421
2019-20
VISVESVARAYA TECHNOLOGICAL UNIVERSITY “JnanaSangama”, Belgaum: 590018
Outer Ring Road, Bellandur, Bengaluru - 560103
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
CERTIFICATE
Certified that the Project work entitled “AUTOMATIC POWER FACTOR CORRECTION” carried out by KARTHIK K (1NH16EE063), ANIL TIKOTI (1NH17EE403), SHUBHAM MISHRA (1NH17EE421), bonafide Student(s) of New Horizon College of Engineering submitted report in the partial fulfillment for the award of Bachelor of Engineering in Department of Electrical and Electronics Engineering, New Horizon College of Engineering of Visvesvaraya Technological University, Belgaum during the Year 2019-20.
It is certified that all the corrections / suggestions indicated for Internal Assessment have been incorporated in the report deposited in the department library. The project report has been approved as it satisfies the academic requirements in respect of project work prescribed for said Degree.
Project Guide Head of the Principal Department Prof. RAMAKRISHNA Dr. S.RAMKUMAR Dr. MANJUNATHA
SEMESTER END EXAMINATION
Internal Examiner External Examiner DECLARATION
We KARTHIK K, ANIL TIKOTI, SHUBHAM MISHRA, students of New Horizon “AUTOMATIC POWER FACTOR CORRECTION” is an original and bonafide College of Engineering hereby declare that, this project work entitled work carried out by us at New Horizon College of Engineering in partial fulfillment of Bachelor of Engineering in Electrical and Electronics Engineering of Visvesvaraya Technological University, Belgaum.
I also declare that, to the best of my knowledge and belief, the work reported here in does not form part of any other thesis or dissertation on the basis of which a degree or award was conferred on an earlier occasion by any student.
KARTHIK K 1NH16EE063 ANIL TIKOTI 1NH17EE403 SHUBHAM MISHRA 1NH17EE421
ACKNOWLEDGEMENT
I take this opportunity to convey our gratitude to all those who have been kind enough to offer their advice and provide assistance when needed which has let to the successful completion of the project.
I would like to express our immense gratitude to our Principle, Dr. MANJUNATHA and Dr. S.RAMKUMAR, Head of the department for their constant support and motivation that has encouraged me to come up with this project and also for providing the right ambience for carrying out the work and the facilities provided to me.
We express our thanks to the project guide Prof. Dr. GANESH C, department of Electrical and Electronics Engineering, New Horizon College of engineering for his/her skillful guidance, constant supervision, timely suggestion and constructive criticism in successful completion of my project in time.
We wish to thank all the faculty and para-teaching staff of Electrical and Electronics Engineering Department for providing me all support whenever needed.
Last but not the least we would like to thank all my friends without whose support and co-operation the completion of project would not have been possible.
KARTHIK K 1NH16EE063 ANIL TIKOTI 1NH17EE403 SHUBHAM MISHRA 1NH17EE421
INDEX
1. Introduction
2. Literature Survey
3. Block Diagram
4. Technology 4.1 Zero Crossing Detector 4.2 Solid State Switch 4.3 Capacitor Bank 4.4 Controller Unit 5. Hardware Requirement 6. Software Requirement 7. Expected Circuit Diagram 7.1 Current Transformer 7.2 Potential Transformer 7.1.1 Types Of Potential Transformer 7.1.2 Ratio and Phase Angle Errors of Potential Transformer 7.1.3 Voltage Ratio Error 7.1.4 Phase Angle Error 7.1.5 Burden of Potential Transformer 7.1.6 Phasor Diagram of a Potential Transformer 7.1.7 Applications of Potential Transformer 7.1.8 Voltage Divider 8. Design Calculation 8.1. Calculation of Power Factor Using Theory 8.2. Calculation of Compensated Capacitor Units 8.3. Calculation of Capacitor Discharge Circuit 8.4. Phase Angle by Using Time Difference 8.5. Power Factor Equation for Using Program 9. System Flow Chart 10. Test & Simulation 11. Hardware 11.1 Capacitor Bank 11.2 Switch 11.3 Inductive Loads 11.4 Actuators 12. Working 13. Program 14. Conclusion 15. Reference
List of Figures
3.1 Block diagram 4.1 Power factor curve
4.1.1 Zero Crossing Detector
7.1 Expected Circuit diagram 7.1.1 Phasor diagram of the potential transformer 9.1 Flowchart 10.1 Single phase circuit 10.1.1 Simulation Output 10.1.2 Simulation Output for RMS Voltage
10.1.3 Simulation Output for power
10.1.4 Phase Shift
10.1.5 Power Triangle
10.1.6 Centralized power factor correction
10.1.7 De-Centralized power factor correction
10.1.8 Local power factor correction
10.1.9 Connection Diagram PROJECT PHASE-2(EEE84) |SEM-VIII] AUTOMATIC POWER FACTOR CORRECTION
CHAPTER-1
INTRODUCTION
In electrical plants, the loads draw from the network electric power (active) as power supply source (e.g. personal computers, printers, diagnostic equipment, etc.) or convert it in to other form of energy (e.g. electrical lamp s or stoves) or into mechanical output (e.g. electrical motors). To get this, it is often necessary that the load exchanges with the network (with net null consumption) and there active energy is produced mainly from inductive type this energy, even if not immediately converted into other forms, contributes to increase the total power flowing through in the electrical network, from the generators, all along the conductors, to the users. To smooth such negative effect, the power factor correction of the electrical plants is carried out. The power factor correction obtained by using capacitor banks to generate locally there active energy necessary for the transfer of electrical useful power, allows a better and more rational technical-economical management of the plants.
There are so many industries around the world and so are in Myanmar. Most of the industrial plants are using the inductive loads in infrastructure such as transformers and motors. Among them, the large industrial motors are essentially used in the industrial plants. Induction motors receive the grate reactive power from network for their proper function. Reactive power consumption causes the reduction of voltage offered in the plants and on the other hand, it causes the reduction of power factor of the whole plants. Therefore to improve the power factor is very important for all of the plants and even in the domestic industries and home appliances. According to that point, one of the best methods for the power factor improvement is the power factor correction (PFC) technique.
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CHAPTER-2
LITERATURE SURVEY
Design and analysis of a hysteretic power factor correction:
With the development of the telecommunication industry and the internet demands on reliable, cost- effective on power has grown.
Now a days the telecommunication power system has o/p current of many kilo amperes for 10 modules. The high end server system, which holds 100CPU’s, consumes tens of kilowatts of power. For mission critical applications, communication between modules and system controllers is critical for reliability.
Information about temperature, current and total harmonic distortions of each module will enable the functions such as dynamic temperature controller, fault diagnosis and removal and adaptive controller. It will also enhance function such as current sharing and fault protection.
The dominance of the analog controller at the modular level limits, system module communication. Whereas digital controller is more suitable with its good communication abilities it provides system-modules communication for direct current power supply.
The PFC converter is an important stage for distributed power system. Its controller is the most complex with a 3 loop structure and multiplier / divider. His thesis has given the design method, implementation and cost effectiveness of digital controller for PFC and for advanced PFC controller. It also discusses the influence of digital delay on PFC performance as cost effective solution that achieves good performance is provided. The same effectiveness is verified by simulation.
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This research literature has discussed the optimal controller for range -switch on and range– switch off topologies. This thesis provides an active balance solution to solve our problem.
A digital power factor corrector circuit including a digital comparator that compares the actual direct current, bus voltage of an electrical circuit with a desired direct current, bus voltage to produce a digitally attenuated signal in the form of a pulse width, this modulated signal is used to attenuate the voltage from a time varying source. This attenuates source voltage is used as the current demand signal for a current controller that controls the current drawn from the line. High power factors are desired for various others reasons, including energy efficiency. In general the higher the power factor of a particular load the greater is the efficiency of the load further higher the power factor lesser the load will distort the voltage source provided by the source of electric power. To avoid significant distortions in the voltage wave form provided by the power utilities, certain countries have promulgated regulation requiring electrical equipment above a certain power rating and to have minimum power factor losses.
In real time applications electrical circuits do not have unity power factor. In certain applications such as motor controller circuit that either uses an invertors or convertor operating from direct current bus, the power factor can vary significantly far from unity. Such circuits make use of a combination of a full wave rectifier and a relatively large direct current bus capacitor. This converts sinusoidal alternating input voltage into substantially constant uni directional voltage. In such applications power factor correction circuits are mainly used only for power factor correction purpose. A power factor correction circuit for improving power factor of any electric circuit including a dc bus, where in the electric circuit operates from an Ac source the power factor correction circuit will consist of it.
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A] A rectifier coupled to the AC source for providing rectified voltages.
B] A switching device for providing current path from positive output of the rectifier.
C] A current sensor foe sensing current in the path of current flow.
D] A pulse width modulation controller attenuator coupled to the output of the rectifier.
E] A current controller coupled to the current sensor.
The method for improving the power factor of the electrical circuit that receive supply from a time varying voltage source, the method consists the steps:
A] Comparing the actual direct current bus voltage to the desired direct current bus voltage and providing a digital signal indication.
B] If the desired dc is greater than the actual dc. The n increasing the count on a periodic basis whenever the desired direct current bus voltage becomes greater than the actual direct current and decreasing the count when the desired dc becomes less than the actual dc.
C] Generation of a pulse width modulation signal with a duty cycle that correspond to the count.
D] Now the source signal is attenuated corresponding to the duty cycle of the pulse width modulation signal.
E] Finally the actuating of a switching device coupled to the electrical circuit to draw a current that is in phase with the attenuated source voltage having a magnitude corresponding to that of the attenuated source voltage.
A novel approach to the stability analysis of boost power factor.
They analyzed in their thesis the stability of power factor correction circuit using a hybrid model. They considered 2 loop controllers to control the power stage.
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For each closed loop system, they treated two separate cases:
1] One for which the switching frequency is approaching infinity. 2] One for which it is finite but large.
Unlike previous analysis the analysis on this paper investigates the stabilities of the corrector circuit in the saturated as well as the unsaturated regions. They derive conditions for which a trajectory will reach a smooth hyper surface. If the trajection does not reach a sliding surface, then the system saturates. For this system they have shown that the onset of the fast scale stabilities not only at the peak but also when the inductor current approaches zero. And they have developed a condition which ensures that the saturated region do not have any stable orbits as such. Now coming to the second closed loop they use a controller gain for current loop as bifurifaction parameters to show the mechanism of the torus break down.
Once the mechanism for the torus break down is known then depending on the post-instabilities dynamics a designer can optimize the design of a closed loop controller.
To understand the term power factor let us start with the definitions of more basic terms: KW is working power (also called Actual Power or Active Power or Real Power). It is the power that actually powers the equipment and performs useful work. KVAR is reactive power. It is power that magnetic equipment (transformer, motor and relays) need to produce the magnetic flux. KVA is apparent power. It is the vectorial summation of KVAR and KW. Since power factor is defined as the ratio of KW to KVA, we seal low power factor result when KW is small in relation to KVA. Remembering the analogy, this would occur when KVAR is large.
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What causes a large KVAR in a system? The answer is inductive load which source of reactive power:
1) %Transformer
2) %induction motor
3) %Induction Generators
4) %High Intensity Discharge
Some benefits of improving power factor are:-
Recalling that the inductive loads which require reactive power caused the low power factors. This increase in required reactive power causes an increase in required apparent power which is what the utility is supplying.
So, a facility’s low power factor causes the utility to have increased its generation and transmission capacity in order to handle its extra demand. By raising the power factor we are using less KVAR. This results in less KW which equate to saving a rupee from the utility.
Increased system capacity and reduced system losses in our electrical system are done by adding capacitors to the system. Hence the power factor is improved and the KW capacity of the system is increased.
Uncorrected power factors cause power system losses in the distribution system. Thus by improving the power factor, these losses can be reduced. With the current rise in the cost of electrical energy, increased facility efficiency is very desirable. And with lower system losses we will be able to add additional load to our system.
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Thus it comes as no surprise that one way to increase the power factor is by adding capacitors to the system. The other way of increasing power factor is inductive and capacitive react 180 degrees to each other. Capacitors stores KVAR’ sand release opposing there active energy caused by the inductor.
The presence of both the capacitor and inductor in the same electrical circuit results in the continuous alternating transfer of energy between the two.
Thus when the circuit is balanced, all the energy released by the inductor is absorbed by the capacitor.
Power Factor Correction:-
Normal power factor------0.5 to 0.6
Power factor after correction ------0.9 to 0.99
How is power factor corrected------adding capacitor bank
Maximum variation in power factor-----0.2 to 0.3 PROJECT PHASE-2(EEE84) |SEM-VIII] AUTOMATIC POWER FACTOR CORRECTION
The power factor control device and device is useful in the improvement of the efficient transmission of the active power. This PFC are popular because of the advantage such as high power factors, fast dynamic response and low cost. Digital PFC is more desirable because they have many advantages over the analog controllers due to their program ability, flexibility no temperature and adding effect and more resistant to input voltage distortion.
Power factor correction using capacitor banks reduce reactive power consumption which will lead to minimization of losses and at the same time increase the electrical system’s efficiency. Power saving issues and power management has led to the development of single phase capacitor banks for domestic and industrial applications.
The development of this project is to enhance and upgrade the operation of single phase capacitor banks by developing a microprocessor based control system. The output of this device which is obtained from the simulation result and hardware implementation will be analyzed to see the effect of controlling and controlling and correcting activity.
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CHAPTER - 3
BLOCKDIAGRAM
Fig 3.1 Block diagram
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CHAPTER - 4
TECHNOLOGY
This system presents power factor correction (PFC) technique using solid state switched capacitors. This system describes the design and simulation of power factor correction using Arduino UNO controller. Measuring the power factor from the load by using LM358 zero crossing circuit and CD 4070 BC phase shift detector, and then calculating the power factor have been done according to the program and LCD will be used for display. If the power is not in the range, the switches are on/off conditioned by the controller unit and capacitors are activate / deactivate and improve the power factor. This system provides implementation one on Arduino UNO micro controller using C language software to program the micro controller, Arduino program to determine time lag between current and voltage and Proteus 7.7 to simulate the power factor according to the load.
The apparent power also referred to as total power delivered by utility company has two components.
(1) Productive Power that powers the equipment and performs the useful work. It is measured in KW (kilowatts).
(2) Reactive Power that generates magnetic fields to produce flux necessary for the operation of induction devices (AC motors, transformer, inductive furnaces, ovens etc.) It is measured in kVAR (kilovolt-Ampere-Reactance).
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Reactive Power produces no productive work. An inductive motor with power applied and no load on its shaft should draw almost nil productive power, since no output work is being accomplished until a load is applied. The current associated with no-load motor readings is almost entirely "Reactive" Power. As a load is applied to the shaft of the motor, the" Reactive" Power requirement will change only a small amount. The Productive Power is the power that is transferred from electrical energy to some other form of energy (i.e. such as heat energy or mechanical energy). The apparent power is always in excess of the productive power for inductive loads and is dependent on the type of machine in use. The working power (kW) and reactive power (kVAR) together make up apparent power, which is measured in kilovolt amperes (kVA). Graphically it can be represented as:
Power factor =
Fig 4.1 Power factor curve The cosine of the phase angle θ between the kVA and the kW components represents the power factor of the load. kVAR represents the non-productive reactive power and θ is lagging phase angle[1].
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The Relationship between kVA, kW and kVAR is non-linear and is expressed: kVA2 = kW2 + kVAR2
Benefits of Power Factor Correction are: (1) Reduce Utility Power Bills, (2) Increase System Capacity,
(3) Improve System Operating Characteristics (Gain Voltage), and (4) Improve System Operating Characteristics (Reduce Line Losses).
8.1 Zero Crossing Detector
Zero crossing detector is used to detect in e wave zero crossing from positive half cycle to negative half cycle or negative half cycle. To measure time difference between two waves is to detect zero crossing of two waves. The 230V, 50Hzis step down educing voltage transformer and current transformer is used to extract the wave forms of current. The output of the voltage transformer is proportional to the voltage across the load and output of current transformer is proportional to the current through the load. These wave forms are fed to voltage comparators construct educing operational amplifier. It is a zero crossing detector, and its output changes during zero crossing of the current and voltage waveforms. These outputs are fed to the controller unit which does the further power factor calculations.
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Fig 4.1.1 Zero Crossing Detector
Solid state switches are electronic switching devices that can operate on or off positions when a small external voltages is applied from the micro controller. InAC circuits, solid state relays (SCRorTRIAC) switch on at the points of zero load current. The circuit will never be interrupted in the middle of a sine wave peak, preventing the large transient voltages that would otherwise occur due to sudden collapse of them a gnetic field around the inductance. This feature is called zero- crossover switching. Many advantages appear by using the solid state switches in this system. There are slimmer profile, allowing tighter packing, totally silent operation and switch faster than electro mechanical relays; the switching time of a typical optically coupled SSR is dependent on the time needed to power the LED on and off of the order of micro seconds to milli seconds. It can increase lifetime, even if it is activated many times, as there are no moving parts to wear and no contacts to pitor buildup carbon. Output resistance remains constant regardless amount of use. Clean, bounce less operation, no sparking, allows it to be used in explosive environments,
Where it is critical that no spark is generated during switching. It is inherently smaller than a mechanical relay of similar specification. It is much less sensitive to storage and operating environment factors such as mechanical shock, vibration, humidity, and external magnetic fields.
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8.2 Capacitor Bank
There are two categories of connecting capacitor bank. They are shunt and series connecting. Among these two categories, shunt capacitors are more commonly used in the power system of all voltage levels. There are some specific advantages of using shunt capacitors such as:
(1) It reduces line current of the system. (2) It improves voltage level of the load. (3) It also reduces system losses. (4) It improves power factor of the source current.
(5) It reduces load of the alternator. (6) It reduces capital investment per megawatt of the load.
All the above – mentioned benefits come from the fact that the effect of capacitor reduces reactive current flowing through the whole system. Shunt capacitor draws almost fixed amount of leading current which is super imposed on the load current and consequently reduces reactive components of the load and hence improves the power factor of the system. Series capacitor on the other hand has no control.
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Over flow of current. As these are connected in series with load, the load current always passed through series capacitor bank. The capacitive reactance of series capacitor neutralizes the inductive reactance of the line hence, reduces, effective reactance of the line.
8.3 Controller Unit
Controller unit which represented Arduino UNO is the heart of this Automatic Power Factor Controller, it finds, displays and controls the Power Factor. To correct power factor, first finding the current power factor is needed. It displays the calculated power factor in the LCD display and switches ON the capacitors. The controller calculates the time difference between the zero crossing points of current and voltage, which is directly proportional to the power factor. Moreover it determines the power factor according to the program and to get the desired values by using the compensation of the capacitors. Depending on the power factor range the switches are activating the on stage with the control of the program. The required numbers of capacitors are connected in parallel to the load as required.
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CHAPTER - 5 HARDWARE REQUIREMENT
8.3.1 Microcontroller 8.3.2 Op Amps 8.3.3 LCD 8.3.4 Relays 8.3.5 Relay Driver 8.3.6 Capacitors 8.3.7 Diodes 8.3.8 Transformers
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CHAPTER - 6 SOFTWARE REQUIREMENT
• MatLAB
SGJT YFNF SGVED AVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV
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CHAPTER - 7 EXPECTED CIRCUIT DIAGRAM
Fig 7.1 Expected Circuit diagram
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7.1 Current transformer
A current transformer (CT) is a type of transformer that is used to measure alternating current (AC). It produces a current in its secondary which is proportional to the current in its primary.
Current transformers, along with voltage or potential transformers, are instrument transformers. Instrument transformers scale the large values of voltage or current too small, standardized values that are easy to handle for measuring instruments and protective relays. The instrument transformers isolate measurement or protection circuits from the high voltage of the primary system. A current transformer provides a secondary current that is accurately proportional to the current flowing in its primary. The current transformer presents an egligible load to the primary circuit.
Current transformers are the current-sensing units of the power system and are used at generating stations, electrical substations, and in industrial and commercial electric power distribution.
7.2 Potential Transformer The potential transformer may be defined as an instrument transformer used for the transformation of voltage from a higher value to the lower value. This transformer step down the voltage to a safe limit value which can be easily measured by the ordinary low voltage instrument like a voltmeter, wattmeter and watt-hour meters, etc.
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7.2.1 Types Of Potential Transformer
The potential transformer is mainly classified into two types, i.e., the conventional wound types (electromagnetic types) and the capacitor voltage potential transformers.
Conventional wound type transformer is very expensive because of the requirement of the insulations. Capacitor potential transformer is a combination. Of capacitor potential divider and a magnetic potential transformer of relatively small ratio.
The circuit diagram of the capacitor potential transformers shown in the figure below. The stack of high voltage capacitor from the potential divider, the capacitors of two sections become C1and C2, and the Z is the burden. Capacitor -potential- transformer-circuit-diagram.
The voltage applied to the primary of the intermediate transformer is usually of the order 10kV. Both the potential divider and the intermediate transformer have the ratio and insulation requirement which are suitable for economical construction. The intermediate transformer must be of very small ratio error, and phase angle gives the satisfactory performance of the complete unit. The secondary terminal voltage is given by the formula shown below.
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7.2.2 Ratio and Phase Angle Errors of Potential Transformer
In an ideal potential transformer, the primary and the secondary voltage is exactly proportional to the primary voltage and exactly in phase opposition. But this cannot be achieved practically due to the primary and secondary voltage drops. Thus, both the primary and secondary voltage is introduced in the system.
7.2.3 Voltage Ratio Error–
The voltage ratio error is expressed in regarding
Measured voltage, and it is given by the formula as shown below
Where Kn is the nominal ratio, i.e., the ratio of the rated primary voltage and the rated secondary voltage.
7.2.4 Phase Angle Error –
The phase angle error is the error between the secondary terminal voltage which is exactly in phase opposition with the primary terminal voltage.
The increases in the number of instruments in the relay connected to the secondary of the potential transformer will increase the errors in the potential transformers.
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7.2.5 Burden of a potential Transformer
The burden is the total external volt-amp load on the secondary at rated secondary voltage. The rated burden of a PT is a VA burden which must not be exceeded if the transformer is to operate with its rated accuracy. The rated burden is indicated on the nameplate.
The limiting or maximum burden is the greatest VA load at which the potential transformer will operate continuously without over heating its windings beyond the permissible limits. This burden is several times greater than the rated burden.
7.2.6 Phasor Diagram of a Potential Transformer
The phasor diagram of the potential transformer is shown in the figure below.
Fig 7.1.1 phasor diagram of the potential transformer
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Where, Is–secondary current Es – secondary induced mf Vs–secondary terminal voltage Rs – secondary winding resistance Xs–secondary winding reactance Ip–Primary current Ep – primarily induced emf Vp – primary terminal voltage Rp–primary winding resistance Xp–primary winding reactance Kt – turn ratio Io – excitation current Im–magnetizing component of Io Iw–core loss component of Io Φm – mainf lux Β- phase angle error
The main flux is taken as a reference. In instrument transformer, the primary current is the vector sum of the excitation current Io and the current equal to the reversal secondary current Is multiplied by the ratio of 1/kt. The Vp is the voltage applied to the primary terminal of the potential transformer.
The voltage drops due to resistance and reactance of primary winding due to primary current is given by Ip Xp and Ip Rp. When the voltage drop subtracts from the primary voltage of the potential transformer, the primarily induced emf will appear across the terminals.
This primary emf of the transformer will transform into secondary winding by mutuall induction and converted into secondary induced emf Es.This emf will drop by the secondary winding resistance and reactance, and the resultant voltage will appear across the secondary terminal voltage, and it is denoted by Vs.
23 7.2.7 Applications of Potential Transformer
• It is used for a metering purpose. • For the protection of the feeders.
• For protecting the impedance of the generators. • For synchronizing the generators and feeders.
The potential transformers are used in the protecting relaying scheme because the potential coils of the protective device are not directly connected to the system in case of the high voltage. Therefore, it is necessary to step down the voltage and also to insulate the protective equipment from the primary circuit.
7.2.8 Voltage Divider
In electronics, a voltage divider (also known as a potential divider) is a passive linear circuit that produces an output voltage (V out) that is a fraction of its input voltage (V in). Voltage division is the result of distributing the input voltage among the components of the divider. A simple example of a voltage divider is two resistors connected in series, with the input voltage applied across the resistor pair and the output voltage emerging from the connection between them.
Resistor voltage dividers are commonly used to create reference voltages, or to reduce the magnitude of a voltages o it can be measured and may also be used as signal attenuators at low frequencies. For direct current and relatively low frequencies, a voltage divider may be sufficiently accurate if made only of resistors; where frequency response over a wide range is required (such as in an oscilloscope probe), a voltage divider may have capacitive elements added to compensate load capacitance. In electric power transmission, a capacitive voltage divider is used for measurement of high voltage.
E Z1 in parallel with Z2 (sometimes written Z1 // Z2), that is: (Z1 Z2) / (Z1 + Z2) = HZ1.
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To obtain a sufficiently stable output voltage, the output current must either be stable (and so be made part of the calculation of the potential divider values) or limited to an appropriately small percentage of the divider's input current. Load sensitivity can be decreased by reducing the impedance of both halves of the divider, though this increases the divider's quiescent input current and results in higher power consumption (and wasted heat) in the divider. Voltage regulators are often used in lieu of passive voltage dividers when it is necessary to accommodate high or fluctuating load currents.
Voltage dividers are used for adjusting the level of a signal, for bias of active devices in amplifiers, and for measurement of voltages. A Wheat stone bridge and a multi meter both include voltage dividers. A potentiometer is used as a variable voltage divider in the volume control of many radios.
Voltage dividers can be used to allow a micro controller to measure the resistance of a sensor. The sensor is wired in series with a known resistance to form a voltage divider and a known voltage is applied across the divider. The micro controller's analog-to-digital converter is connected to the center tap of the divider so that it can measure the tap voltage and, by using the measured voltage and the known resistance and voltage, compute the sensor resistance. An example that is commonly used involves a potentiometer (variable resistor) as one of the resistive elements. When the shaft of the potentiometer is rotated the resistance it produces either increases or decreases, the change in resistance corresponds to the angular change of the shaft. If coupled with a stable voltage reference, the output voltage can be fed into an analog-to-digital converter and a display can show the angle. Such circuits are commonly used in reading control knobs. Note that it is highly beneficial for the potentiometer to have a linear taper, as the micro controller or other circuit reading the signal must otherwise correct for the non-linearity in its calculations.
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7.2.9 High voltage measurement
A voltage divider can be used to scale down a very high voltage so that it can be measured by a voltmeter. The high voltage is applied across the divider, and the divider output—which outputs a lower voltage that is within the meter's input range is measured by the meter. High voltage resistor divider probes designed specifically for this purpose can be used to measure voltages upto100kV. Special high-voltage resistors are used in such probes as they must be able to tolerate high input voltages and, to produce accurate results, must have matched temperature coefficients and very low voltage coefficients. Capacitive divider probes are typically used for voltages above100kV, as the heat caused by power losses in resistor divider probes at such high voltages could be excessive.
7.2.10 Logic level shifting
A voltage divider can be used as a crude logic level shifter to interface two circuits that use different operating voltages. For example, some logic circuits operate at 5V where as others operate at 3.3V. Directly interfacing a 5Vlogic output to a 3.3V input may cause permanent damage to the 3.3V circuit. In this case, a voltage divider with an output ratio of 3.3/5 might be used to reduce the 5V signal to 3.3V, to allow the circuits to inter operate without damaging the 3.3V circuit. For this to be feasible, the 5V source impedance and 3.3V input impedance must be negligible, or they must be constant and the divider resistor values must account for their impedances. If the input impedance is capacitive, a purely resistive divider will limit the data rate. This can be roughly overcome by adding a capacitor in series with the top resistor, to make both legs of the divider capacitive as well as resistive.
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7.2.11 Bridge Rectifier
A bridge rectifier circuit is a common part of the electronic power supplies. Many electronic circuits require rectified DC power supply for powering the various electronic basic components from available AC mains supply. We can find this rectifier in a wide variety of electronic AC power devices like home appliances, motor controllers, modulation process, welding applications, etc.
A Bridge rectifier is an Alternating Current (AC) to Direct Current (DC) converter that rectifies mains AC input to DC output. Bridge Rectifiers are widely used in power supplies that provide necessary DC voltage for the electronic components or devices. They can be constructed with four or more diodes or any other controlled solid-state switches. Depending on the load current requirements, a proper bridge rectifier is selected. Component’s ratings and specifications, breakdown voltage, temperature ranges, transient current rating, forward current rating, mounting requirements and other considerations are considered while selecting a rectifier power supply for an appropriate electronic circuit’s application.
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CHAPTER – 8
DESIGN CALCULATION
8.1 Calculation of Power Factor Using Theory
In this system, the selected loads are as follow Selected values for Motor1 R=50Ω, L=200mH, f=50Hz Selected values for Motor2 R=50Ω, L=250mH, f=50Hz Selected values for Motor3 R=50Ω, L=200mH, f=50Hz Motor 1 ON, supply voltage, V= 230 ∠0 ˚V Z1=R+ jωl=R+j2πfl Z1= (50+j20π)Ω=80.29845∠51.488°Ω I= V/Z1 =2.864∠-51.488°A P.F=cos(51.488)=0.6227(Lagging)
Motor1, Motor2 and Motor3 ON, supply, =2300˚
=28.08553.3041°AΩ A (Lagging)
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8.2 Calculation of Compensated Capacitor Units This calculation describes the compensated capacitors for different conditions. Motor1 ON V=230V, I=2.864∠51.68 A Initial power factor =
Target power factor= ˚
= P (tan53.13-tan19.95) =408.41 (tan 51.46 – tan 19.95) =367.569Var
For capacitor,
= =
Motor1, 2 and 3 on V=230V, I=8.1989 Initial power factor = Target power factor = P=VI cos =230×8.1989×0.6 =1131.4482 W Qc = Q1-Q2 =P (tanθ1-tanθ2)= 1131.4482 (tan53.13-tan19.95) =1097.896 Var
For Capacitor,
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8.3 Calculation of Capacitor Discharge Circuit
This section describes the calculation of capacitor discharge circuit:
Supply Voltage,
Vc (max) = 325V
Select Discharge Time t = 2 sec
Vc (min) =10%Vc(max)=10%of325V=32.5V
For C2= 2.2µF, 2 Discharge Resistor, R1 = = 395.26kΩ 2.3∗2.2∗10−6 Select R1=390kΩ
For C2=4.7µF, 2 Discharge Resistor, R2 = = 185.01kΩ 2.3∗4.7∗10−6 Select R2=180kΩ
For C3=22µF, 2 Discharge Resistor, R3= = 39.53kΩ 2.3∗22∗ 10−6 Select R3=39kΩ
For C4=7µF, 2 Discharge Resistor, R4= =18.5kΩ 2.3∗47∗10−6 Select R4=18kΩ
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8.4 Phase Angle by Using Time Difference For example,
For half cycle
180˚ → 10 ms 1˚
55.556 µs time difference is the 1˚ phase shift. 60˚phase ft→
=3333.36 µs
8.5 Power Factor Equation for Using Program T=Time duration between V and I waveform θ = Phase shift P.F =cosθ (Deg:)
(Rad:)
P.F = cos θ 31 =cos ( )
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CHAPTER-9 SYSTEM FLOWCHART
11.TEST&SIMULATIONCIRCUIT
Fig 9.1 Flowchart
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CHAPTER - 10 TEST & SIMULATION
Fig 10.1 Single phase circuit
Fig 10.1.1 Simulation Output
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Fig 10.1.2 Simulation Output for RMS Voltage
Fig 10.1.3 Simulation Output for power
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CHAPTER – 11 HARDWARE
11.1 CAPACITOR BANK
In certain circumstances such currents can exceed the value of the fundamental (50Hzor60Hz) capacitor current. These currents in turn cause increased voltage o be applied across the dielectric of the capacitor. The harmonic voltage due to each harmonic current added arithmetically to the fundamental voltage dictates the voltage stress to be sustained by the capacitor dielectric and for which the capacitor must be designed, to avoid additional heating and higher dielectric stress.
Capacitors may catastrophically fail when subjected to voltages or currents beyond their rating, or as they reach their normal end of life. Dielectric or metal inter connection failures may create arcing that vaporizes the dielectric fluid, resulting in that case bulging, rupture, or even an explosion.
Capacitors units are intended to be operated at or below their rated voltage and frequency.
IEEE Std. 18-1992 and Std. 1036-1992 specifies the standard ratings of the capacitors designed for shunt connection to ac systems and provide application guidelines. These standards stipulate that:
Capacitor units should be capable of continuous operation upto110% of rated terminal rms [5] voltage and ac rest (peak) voltage not exceeding 2x√2 of rated rms voltage, including harmonics but excluding transients. The capacitor should also be able to carry 135% of nominal current. Capacitors units should not give less than 100% and more than 115% of rated reactive power at rated sinusoidal voltage and frequency. Capacitor units should be suitable for continuous operation at upto135% of rated reactive power caused by the combined effects of:
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Voltage in excess of the name plate rating at fund a mental frequency, but not over 110% of rated rms voltage. Harmonic voltages superimposed on the fundamental frequency: reactive power manufacturing tolerance of upto115% of rated reactive power. Capacitor banks characteristics and application harmonic problems exist, they most often manifest themselves first at shunt capacitor banks in the form of audible noise, blown fuses or capacitor unit failures.
As frequency varies, so reactance varies, and a point can be reached when the capacitor reactance and the supply reactance are equal. This point is known as the circuit resonant frequency.
Whenever power factor correction is applied to a distribution network, bringing together capacitance and inductance, there will always be a frequency at which the capacitors are in parallel resonance with the supply.
If this condition occurs at, or close to, one of the harmonics generated by any solid- state control equipment, then large harmonic currents can circulate between the supply network and the capacitor equipment, limited only by the damping resistance in the circuit. Such currents will add to the harmonic voltage disturbance in the network causing an increased voltage distortion.
This result in an unacceptably high voltage across the capacitor dielectric coupled with an excessive current through all the capacitor ancillary components. The most common order of harmonics is 5th, 7th, 11th and 13th but resonance can occur at any frequency. Capacitors can be effectively applied in these types of environments by selecting compensation levels that do not tune the circuit or using a filter.
POWER FACTOR CORRECTION
In electrical installations, namely in industry, exists several consumers, such as motors, that have an important inductive load that provokes a phase shift between voltage and current, as show on the figure below.
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Fig 10.1.4 Phase Shift
11.1.1 Phase shift
Phase shift is represented as an angle (Ф) and current may be in advance or delayed of voltage.
If capacitance of the circuit prevails current is advanced; If inductance prevails current is delayed.
This phase shift provokes that “useful power” (active power–unit: Work W) is lower than the power supplied (apparent power–unit: VA or kVA), the difference being the reactive power–unit: VAr or kVAr.
11.1.2 Power triangle
Fig 10.1.5 Power Triangle 38 PROJECT PHASE-2(EEE84)|SEM-VIII AUTOMATIC POWER FACTOR CORRECTION
The cosine of Ф (cos Ф) is the power factor, its value varies from 0 to 1 and the relations between the powers in the above triangle are:
P=Sx cos Φ
Q=Sx sin Φ
The consequences of a low power factor are:
• Higher currents in cables. • Higher losses by Joule effect in the conductors. • Higher voltage drops
In most countries electricity distribution companies do not allow power factor to be lower than a defined value (in Europe it must be cosФ≥0.93<>tgФ≤0.4) and impose penalties to clients that do not comply with this requirement.
When correcting power factor, clients avoid those penalties and in addition the reduction of losses can provide the utility with the additional benefit of reducing the apparent substation demand during peak loading conditions and the released system capacity can then be used to deliver more real power from the existing system, resulting in a more efficiently run power system.
Also, the cross-section of the conductors can be reduced as advantage by improving the power factor.
When installing capacitor banks, it is necessary to:
• Calculate the bank size (the size of a capacitor bank is defined kVAr) • Determine the location for connection. • Select a control method. To calculate the size of the capacitor bank (Q), the following equation must be used:
You may also convert the capacitor bank kVAr and Farads as well.
Q [kVAr] = P [kW] x (tan Ф1 – tan Ф2)
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P is the active power of the installation; Ф1 is the voltage and current phase shift of the installation; Ф2 is the desired voltage and current phase shift.
To define the location of the capacitor bank it must be taken into account that three methods are used for power factor correction, which depends of the location of the inductive loads and their requested reactive power:
Centralized correction: one capacitor bank is installed near the main in coming switchboard • De-centralized correction: capacitor banks are installed near distribution switch boards that supply energy to the main consumers responsible for the low power factor (see Figure8). • Local correction: capacitor banks are installed near individual consumers (seeFigure9). • Centralized power factor correction centralized Power Factor (p.f.) correction.
Fig 10.1.6 Centralized power factor correction
For MV installations capacitor banks may be divided in steps and controlled by a VAR relay or an electronic controller, that monitors and switches steps or the whole capacitor bank based on real time network conditions, to avoid the supply of reactive power to the network, situation that is also subjected to open all ties applied by the electricity distribution companies.
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Fig 10.1.7 De-Centralized power factor correction
Fig 10.1.8 Local power factor correction
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Fig 10.1.9 Connection Diagram
11.2 Switch
A switch is an electrical component that can "make" or "break" an electrical circuit, interrupting the current or diverting it from one conduct or to another. [1][2] The mechanism of a switch removes or restores the conducting path in a circuit when it is operated. It may be operated manually, for example, alight switch or a keyboard button, may be operated by a moving object such as a door, or may be operated by some sensing element for pressure, temperature or flow. A switch will have one or more sets of contacts, which may operate simultaneously, sequentially, or alternately. Switches in high-powered circuits must operate rapidly to prevent destructive arcing and may include special features to assisting rapidly interrupting a heavy current. Multiple forms of actuators are used for operation by hand or to sense position, level, temperature or flow. Specialty pes are used, for example, for
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Control of machinery, to reverse electric motors, or to sense liquid level. Many specialized forms exist. A common use is control of lighting, where multiple switches may be wired into one circuit to allow convenient control of light fixtures.
By analogy with the devices that select one or more possible paths for electric currents, devices that route information in a computer network are also called "switches" - these are usually more complicated than simple electromechanical toggles or push button devices and operate without direct human interaction.
Description
The most familiar form of switch is a manually operated electro mechanical device with one or more sets of electrical contacts, which are connected to external circuits. Each set of contacts can be in one of two states: either "closed" meaning the contacts are touching and electricity can flow between them, or "open", meaning the contacts are separated and the switch is non conducting. The mechanism actuating the transition between these two states (open or closed) are usually (there are other types of actions) either an" alternate action" (flip the switch for continuous "on" or "off") or “momentary" (push for "on" and release for "off") type.
A switch may be directly manipulated by a human as a control sign alto a system, such as a computer key board button, or to control power flow in a circuit, such as a light switch. Automatically operated switches can be used to control the motions of machines, for example, to indicate that a garage door has reached its full open position or that a machine tool is in a position to accept another workpiece. Switches may be operated by process variables such as pressure, temperature, flow, current, voltage, and force, acting as sensors in a process and used to automatically control a system. For example, a thermostat is a temperature- operated switch used to control a heating process. A switch that is operated by another electrical circuit is called a relay. Large switches may be remotely operated by a motor drive mechanism. Some switches are used to isolate electric power from a system, providing a visible point of isolation that can be pad locked if necessary to prevent accidental operation of a machine during maintenance, or to prevent electric shock.
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An ideal switch would have no voltage drop when closed and would have no limits on voltage or current rating. It would have zero rise time and fall time during state changes and would change state without "bouncing" between on and off positions.
Practical switches fall short of this ideal; they have resistance, limits on the current and voltage they can handle, finite switching time, etc. The ideal switch is often used in circuit analysis as it greatly simplifies the system of equations to be solved, but this can lead to a less accurate solution. Theoretical treatment of the effects of non-ideal properties is required in the design of large networks of switches, as for example used in telephone exchanges.
11.2.1 Contacts
In the simplest case, a switch has two conductive pieces, often metal, called contacts, connected to an external circuit, that touch to complete (make) the circuit, and separate to open (break) the circuit. The contact material is chosen for its resistance to corrosion, because most metals form insulating oxides that would prevent the switch from working. Contact materials are also chosen on the basis of electrical conductivity, hardness (resistance to abrasive wear), mechanical strength, low cost and low toxicity.
Sometimes the contacts are plated with noble metals, for their excellent conductivity and resistance to corrosion. They may be designed to wipe against each other to clean off any contamination. Nonmetallic conductors, such as conductive plastic, are sometime sused. To prevent the formation of insulating oxides, a minimum wetting current may be specified for a given switch design.
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11.2.2 Contact Terminology
In electronics, switches are classified according to the arrangement of their contacts. A pair of contacts is said to be "closed" when current can flow from one to the other. When the contacts are separated by an insulating air gap, they are said to be "open", and no current can flow between them at normal voltages. The terms "make" for closure of contacts and "break" for opening of contacts are also widely used.
The terms pole and throw are also used to describe switch contact variations. The number of "poles" is the number of electrically separate switches which are controlled by a single physical actuator. For example, a"2-pole" switch has two separate, parallel sets of contacts that open and close in unisonvia the same mechanism. The number of "throws" is the number of separate wiring path choices other than "open" that the switch can adopt for each pole. A single-throw switch has one pair of contacts that can either be closed or open. A double- throw switch has a contact that can be connected to either of two other contacts, a triple-throw has a contact which can be connected to one of three other contacts, etc.
In a switch where the contacts remain in one state unless actuated, such as a push- button switch, the contacts can either be normally open (abbreviated "n. o." or "no") until closed by operation of the switch, or normally closed ("n. c." or " nc") and opened by the switch action. A switch with both types of contact is called a changeover switch or double-throw switch. These may be "make- before-break" ("MBB" or shorting) which momentarily connects both circuits or maybe "break-before-make" ("BBM" or non-shorting) which interrupts one circuit before closing the other.
These term shave given rise to abbreviations for the types of switch which are used in the electronics industry such as "single-pole, single-throw" (SPST) (the simplest type, "on or off") or "single-pole, double-throw" (SPDT), connecting either of two terminals to the common terminal. In electrical power wiring (i.e., house and building wiring by electricians), names generally involve the suffix "- way"; however, these terms differ between British English and American English (i.e., the terms two way and three way are used with different meanings).
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11.2.3 Contact bounce
Contact bounce (also called chatter) is a common problem with mechanical switches and relays. Switch and relay contacts are usually made of springy metals. When the contacts strike together, their momentum and elasticity act together to cause them to bounce apart one or more times before making steady contact. The result is a rapidly pulsed electric current instead of a clean transition from zero to full current. The effect is usually unimportant in power circuits, but causes problems in some analogue and logic circuits that respond fast enough to misinterpret the on‑off pulses as a data stream.
The effects of contact bounce can be eliminated by use of mercury-wetted contacts, but these are no win frequently used because of the hazard of mercury release. Alternatively, contact circuit voltages can below-pass filtered to reduce or eliminate multiple pulses from appearing. In digital systems, multiple samples of the contact state can be taken to a low rate and examined for a steady sequence, so that contacts can settle before the contact level is considered reliable and acted upon. Bounce in SPDT switch contacts signals can be filtered out using a SR flip-flop (latch) or Schmit ttrigger. All of these methods are referred to as 'de bouncing'.
By analogy, the term "de bounce" has arisen in the software development industry to describe rate-limiting or throttling the frequency of a method's execution. Contact bouncing is used in the Hammond organ and together with the multiple non-synchrony closing contacts under a piano key known as the Hammond Click.
In the Hammond organ, multiple wires are pressed together under the piano keys of the manuals. Their bouncing and non-synchronous closing of the switches is known as Hammond Click and compositions exists that use and emphasize this feature. Some electronic organs have a switch able replica of this sound effect.
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11.2.4 Arcs and quenching
When the power being switched is sufficiently large, the electron flow across opening switch contacts is enough to ionize the air molecules across the tiny gap between the contacts as the switch is opened, forming a gas plasma, also known as an electric arc. The plasma is of low resistance and can sustain power flow, even with the separation distance between the switch contacts steadily increasing. The plasma is also very hot and can erode the metal surfaces of the switch contacts. Electric current arcing causes significant degradation of the contacts and significant electromagnetic interference (EMI), requiring the use of arc suppression methods. Where the voltage is sufficiently high, an arc can also form as the switch is closed and the contacts approach. If the voltage potential is enough to exceed the breakdown voltage of the air separating the contacts, an arc forms which is sustained until the switch closes completely and the switch surfaces make contact. In either case, the standard method for minimizing arc formation and preventing contact damage is to use a fast-moving switch mechanism, typically using a spring- operated tipping-point mechanism to assure quick motion f switch contacts, regardless of the speed at which the switch control is operated by the user. Movement of the switch control ever applies tension to a spring until a tipping point is reached, and the contacts suddenly snap open or closed as the spring tension is released. As the power being switched increases, other methods are used to minimize or prevent arc formation. A plasma is hot and will rise due to convection air currents. The arc can be quenched with a series of non-conductive blades spanning the distance between switch contacts, and as the arc rises, its length increases as it forms ridges rising into the spaces between the blades, until the arc is too long to stay sustained and is extinguished. A puffer may be used to blow a sudden high velocity burst of gas across the switch contacts, which rapidly extends the length of the arc to extinguish it quickly. Extremely large switches more than 100,000‑watt capacity often have switch contacts surrounded by something other than air to more rapidly extinguish the arc. For example, the switch contacts may operate in a vacuum, immersed in mineral oil, or in sulfur hexafluoride.
In AC power service, the current periodically passes through zero; this effect makes it harder to sustain an arc on opening. Manufacturers may rate switches with lower voltage or current rating when used in DC circuits.
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11.2.5 Power Switching
When a switch is designed to switch significant power, the transitional state of the switch as well as the ability to with stand continuous operating currents must be considered. When a switch is in the on state, its resistance is near zero and very little power is dropped in the contacts; when a switch is in the off state, its resistance is extremely high and even less power is dropped in the contacts. However, when the switch is flicked, the resistance must pass through a state where a quarter of the load's rated power [citation needed] (or worse if the load is not purely resistive) is briefly dropped in the switch.
For this reason, power switches intended to interrupt a load current have spring mechanisms to make sure the transition between on and off is as short as possible regardless of the speed at which the user moves the rocker.
Power switches usually come in two types. A momentary on‑off switch (such as on a laser pointer) usually takes the form of a button and only closes the circuit when the button is depressed. A regular on‑off switch (such as on a flash light) has a constant on-off feature. Dual-actions witches in corporate both features.
11.3 Inductive loads
When a strongly inductive load such as an electric motor is switched off, the current cannot drop instantaneously to zero; as park will jump across the opening contacts. Switches for inductive loads must be rated to handle these cases. The spark will cause electromagnetic interference if not suppressed; a snubber network of a resistor and capacitor in series will quell the spark.
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11.3.1 Incan descent loads
A "T-rated" wall switch (the T is for Tungsten filament) that is suited for in can descent loads. When turn e don, an in can descent lamp draws a large in rush current of a bout ten times the steady-state current; as the filament heats up, its resistance rise sand the current decreases to a steady-state value. A switch designed for an incandescent lamp load can with stand this in rush current.
11.3.2 Wetting current
Wetting current is the minimum current needing to flow through a mechanical switch while it is operated to break through any film of oxidation that may have been deposited on the switch contacts. The film of oxidation occurs often in areas with high humidity. Providing enough wetting current is a crucial step in designing Systems that use delicate switches with small contact pressure as sensor inputs. Failing to do this might result in switches remaining electrically "open" due to contact oxidation.
11.4 Actuator
The moving part that applies the operating force to the contacts is called the actuator, and may be a toggle or dolly, a rocker, a push-button or any type of mechanical linkage (see photo).
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11.4.1 Biased switches
A switch normally maintains its set position once operated. A biased switch contains a mechanism that springs it into another position when released by an operator. The momentary push-button switch is a type of biased switch. The most common type is a "push-to-make" (or normally-open or NO) switch, which makes contact when the button is pressed and breaks when the button is released. Each key of a computer key board, for example, is a normally-open "push-to- make" switch. A "push-to-break" (or normally-closed or NC) switch, on the other hand, breaks contact when the button is pressed and makes contact when it is released. An example of a push-to-break switch is a button used to release a door held closed by an electromagnet. The interior lamp of a house hold refrigerator is controlled by a switch that is held open when the door is closed.
11.4.2 Rotary switch
A three-deck stacked rotary switch. Any number of switching elements may be stacked in this manner, by using a longer shaft and additional spacing stand offs between each switching element. A rotary switch operates with at wisting motion of the operating handle with at least two positions. One or more positions of the switch may be momentary (biased with a spring), requiring the operator to hold the switch in the position. Other positions may have hold the position when released. A rotary switch may have multiple levels or "decks" to allow it to control multiple circuits.
One f or m of rotary switch consists of a spindle or "rotor" that has a contact armor "spoke" which projects from its surface like a cam. Ith a sanar ray of terminals, arranged in a circle around the rotor, each of which serves as a contact for the "spoke" through which any one of several different electrical circuits can be connected to the rotor. The switch is layered to allow the use of multiple poles, each layer is equivalent to one pole. Usually such a switch has a detent mechanism, so it "clicks" from one active position to another rather than stalls in an intermediate position. Thus, a rotary switch provides greater pole and throw capabilities than simpler switches do.
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Other types use a cam mechanism to operate multiple independent sets of contacts.
Rotary switches were used as channel selectors on television receivers until the early 1970s, as ranges electors on electrical mete ring equipment, as bands electors on multi-band radios and other similar purposes. In industry, rotary switches are used for control of measuring instruments, switch gear, or in control circuits. For example, a radio-controlled overhead crane may have a large multi-circuit rotary switch to transfer hard-wired control signals from the local manual controls in the cab to the output soft here mote control receiver.
11.4.3 Toggle switch
Large toggle switch, depicted in circuit "open" position, electrical contacts to left; background is1/4"square graph paper.
Bank of toggle switches on a Data General No vamini computer front panel. Toggle switches with the shared cover preventing certain for bidden combinations.
A toggle switch or tumbler switch is a class of electrical switches that are manually actuated by a mechanical lever, handle, or rocking mechanism.
Toggle switches are available in many different styles and sizes and are used in numerous applications. Many are designed to provide the simultaneous actuation of multiple sets of electrical contacts, or the control of large amounts of electric current or mains voltages.
The word "toggle" is a reference to a k in do f mechanism or joint consisting of two arms, which are almost in line with each other, connected with an elbow-like pivot.
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However, the phrase "toggle switch" is applied to a switch with a short handle and a positive snap-action, whether it contains a toggle mechanism or not. Similarly, a switch where a definitive click is heard, is called a" positive on-off switch. A very common use of this type of switch is to switch lights or other electrical equipment on or off. Multiple toggle switches may be mechanically inter locked to prevent for bidden combinations.
In some contexts, particularly computing, a toggle switch, or the action of toggling, is understood in the different sense of a mechanical or software switch that alternates between two states each time it is activated, regardless of mechanical construction. For example, the caps lock key on a computer causes all letters to be generated in capitals after it is pressed once; pressing it a gain reverts to lower- case letters.
Special types
Opened float switch of a dirty water pump Switches can be designed to respond to any type of mechanical stimulus: for example, vibration (the trembler switch), tilt, air pressure, fluid level (a float switch), the turning of a key (key switch), linear or rotary movement (a limit switch or micro switch), or presence of a magneticfield (the red switch). Many switches are operated automatically by changes in some environmental condition or by motion of machinery. A limit switch is used, for example, in machine tools to inter lock operation with the proper position of tools. In heating or cooling systems as ail switch ensures that air flow is adequate induct. Pressure switches respond to fluid pressure.
11.4.4 Mercury tilt switch
The mercury switch consists of a drop of mercury inside a glass bulb with two or more contacts. The two contacts pass through the glass and are connected by the mercury when the bulb is tilted to make the mercury roll on to them. This type of switch performs much better than the ball tilt switch, as the liquid metal connection is unaffected by dirt, debris and oxidation, it wets the contacts ensuring a very low resistance bounce-free connection, and movement and vibration do not produce a poor contact. These types can be used for precision works.
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It can also be used where arcing is dangerous (such as in the presence of explosive vapor) as the entire unit is sealed.
11.4.5 Knife switch
A high-voltage disconnect switch used in an electrical substation. Such switches are used mostly to isolate circuits, and usually cannot break load current. High- voltage switches are available for the highest transmission voltages, upto 1 million volts. This switch is gang-operated so that all three phases are interrupted at the same time. Knife switches consist of a flat metal blade, hinged at one end, with an insulating handle for operation, and a fixed contact. When the switch is closed, current flows through the hinged pivot and blade and through the fixed contact. Such switches are usually not enclosed. The knife and contacts are typically formed of copper, steel, or brass, depending on the application. Fixed contacts may be backed up with a spring. Several parallel blades can be operated at the same time by one handle. The parts may be mounted on an insulating base with terminals for wiring, or may be directly bolted to an insulated switch board in a large assembly. Since the electrical contacts are exposed, the switch is used only where people cannot accidentally come in contact with the switch or where the voltage is solo was to not present a hazard. Knife switches are made in many sizes from miniature switches to large devices used to carry thousands of amperes. In electrical transmission and distribution, gang-operated switches are used in circuits upto the highest voltages.
The disadvantages of the knife switch are the slow opening speed and the proximity of the operator to exposed live parts. Metal-enclosed safety disconnects witches are used for isolation of circuits in industrial power distribution. Sometimes spring- loaded auxiliary blades are fitted which momentarily carry the full current during opening, then quickly part to rapidly extinguish the arc.
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11.4.6 Foot switch
A foot switch is a rugged switch which is operated by foot pressure. An example of use is in the control of a machine tool, allowing the operator to have both hands free to manipulate the work piece. The foot control of an electric guitar is also a footswitch.
11.4.7 Reversing switch
ADPDT switch has six connections, but since polarity reversal is a very common usage of DPDT switches, some variations of the DPDT switch are internally wired specifically for polarity reversal. These cross over switches only have four terminals rather than six. Two of the terminals are inputs and two are outputs. When connected to a battery or other DC source, the 4-way switch selects from either normal or reversed polarity. Such switches can also be used as intermediate switches in a multiway switching system for control of lamps by more than two switches.
11.4.8 Light switches
In building wiring, light switches are installed at convenient locations to control lighting and occasionally other circuits. By use of multiple-pole switches, multiway switching control of a lamp can be obtained from two or more places, such as the ends of a corridor or stair well. A wireless light switch allows remote control of lamps for convenience; some lamps include a touch switch which electronically controls the lamp if touched anywhere. In public buildings several types of vandal resistant switches are used to prevent unauthorized use.
11.4.9 Slide switches
Slide switches are mechanical switches using a slider that moves (slides) from the open (off) position to the closed (on) position.
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11.4.10 Electronic switches
Three push button switches (Tactile Switches). Major scale is inches. See also: Electronic switch a relay is an electrically operated switch. Many relays use an electro magnet to operate a switching mechanism mechanically, but other operating principles are also used. Solid- state relays control power circuits with no moving parts, instead Using a semiconductor device toper form switching-often a silicon-controlled rectifier or tri ac.
The analogue switch uses two MOSFET transistors in a transmission gate arrangement as a switch that works much like a relay, with some advantages and several limitations compared to an electro mechanical relay.
The power transistor (s) in a switching voltage regulator, such as a power supply unit, are used like a switch to alternately let power flow and block power from flowing.
Many people use metonymy to call a variety of devices "switches" that conceptually connect or disconnect signals and communication paths between electrical devices, analogous to the way mechanical switches connect and disconnect paths for electrons to flow between two conductors. Early telephone systems used an automatically operated stronger switch to connect telephone callers; telephone exchanges contain one or more cross bar switches today.
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CHAPTER - 12
WORKING
1. 220 Volt AC Single Phase Supply Voltage 2. For 12V voltage level-Step down Transformer 3. For 2.5V voltage Scaling-Voltage divider-Zero Crossing Detector 4. Zero Crossing Detector–Connected to voltage p into Arduino controller analog pin 5. Current measured using ACS 712 current sensor- Connected between CT and Arduino 6. Reading both voltage and current of various load and Calculating the power factor Value through Arduino connected to 16x2 LCD Display
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CHAPTER - 13 PROGRAM
#include
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CHAPTER – 14 CONCLUSION
The PFC System with solid state switched capacitor is implemented completely. This system will provide for power factor improvement in low voltage system. Arduino UNO controller is very popular at this event, likewise easily to write the program by using the high level language. By the using of solid state switches, it can compare with the mechanical relays, so many reliable and efficient outcome appear. This is the very efficient system for various loads, by using the different sizes of capacitors and triggering the switches which were controlled by the program. Therefore, it is soundly recommended to come out the perfect benefits on the system which will be constructed as mentioned above.
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CHAPTER–15
REFERENCE
[1]. A. Bhatia, 2012, “Power Factor in Electrical Energy Management”, 5272 Meadow Estates Drive, Fair fax, VA 22030-6658, Phone & Fax: 703-988-0088, www.PDHonline.org , www.PDHcenter.com .
[2]. NOKIAN CAPACITORS, September, 2015, “Power Factor Correction”,
[3]. Aashish.G, neharika Kapil and Sheila, M.2014, “Implementation of Thyristor Switched Capacitors for Power Factor Improvement”, ISSN 2231- 1297, Volume4, November3, 2014.
[4]. Shamal padmawar1, and Prof. Anil wamar. 2014, “Power Factor Correction based on PWM waves using PIC”, ISSN: 2348 – 7968, IJISET, Volume.1, Issuse6, August 2014.
[5]. Pranjali Sonje, and Anagha Soman, 2013, “Power Factor Correction Using PIC Micro controller”, ISSN:2277–2008, ISO9001: 2008 Certified Journal, IJEIT, Volume. 3, Issue4, October2013.
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