Technical Brief - Why is a permanently-installed generator load bank a good idea? The main reason is that, when applied to a diesel or gas-fueled engine-generator set, it can often extend the engine’s lifetime and reduce its maintenance costs. A load bank can also serve as a great on-site tool allowing regular and disruption-free exercising and testing of a standby or emergency power system. Many facilities today are designed with emergency power sources capable of handling future loads. As an example, a manufacturing facility may be designed today with an immediate load profile of 400kW, but with consideration to future expansion plans that could double it in size. The design engineer may choose to specify a 1000kW standby generator to allow for the planned expansion and addition of future loads. This could be the most cost- effective design if a future upgrade of the electrical system calculates to be more expensive or difficult to accomplish while the facility is occupied. However, the initial light load on the emergency generator can be detrimental to the engine, as it may cause abnormal wear, inefficient combustion and higher emissions in some cases. The installation of a load bank can remove these negative consequences by automatically applying an artificial load to the generator. For the most efficient design, the load bank control panel can be set to sense the building loads and automatically regulate the load applied to the generator by the load bank. This “active control” can be programmed so that the generator is always loaded to its optimal level, perhaps 80% of the generator's rated output. As the facility expands (and building loads increase), the load bank gradually decreases its load to the generator. Ultimately, the load bank is retained as a generator weekly exercising and/or test tool. As a secondary benefit, this on-site load bank can now be used to simulate loads unto the generator as needed (weekly, monthly, quarterly) without any power interruption to the building occupants. There are two main designs available for a permanently-installed load bank: a skid-mounted load bank, with all components (load elements, control section, fan/motor, etc.) housed within an outdoor-rated enclosure, or a radiator duct-mounted load bank, designed to be installed "in line" with the engine’s cooling airflow. This design provides substantial cost savings as the load bank uses the radiator's airflow for cooling of the load elements (no need for dedicated motors or fans). There are considerations that must be reviewed to arrive at the best solution for a particular installation, but a broad range of available designs generally satisfy most requirements. To learn more about load bank basic components, design and operation, please see the document following this technical brief or call Hurtado.cc. Hurtado.cc represents Simplex, Inc - a manufacturer of various types of load banks for a wide range of applications. P.O. Box 290608 Port Orange, FL 32129-0608 P. 386 690-6361 F. 516 490-1144 www.hurtado.cc What is a Load Bank? Portable Load Bank A Load Bank is a device which develops The “load” of a resistive load an electrical load, applies the load to an bank is created by the con- electrical power source and converts or dis- version of electrical energy to sipates, the resultant power output of the heat by power resistors. This source. A load bank is intended to accu- heat must be dissipated from rately mimic the operational or “real” load the load bank, either by air or which a power source will see in actual ap- by water, by forced means or plication. However, unlike the “real” load, convection. which is likely to be dispersed, unpredict- able and random in value, a load bank pro- In a testing system, a resis- vides a contained, organized and fully con- tive load simulates real-life re- sistive loads, such as lighting trollable load. Consequently, a load bank can be further defined as a self-contained, and heating loads as well as unitized, systematic device which includes the resistive or unity power fac- tor component of magnetic both load elements with control and acces- sory devices required for operation. Where (motors, transformers) loads. the “real” load is served by the power source A “reactive” load includes in- and uses the energy output of the source ductive (lagging power fac- for some productive purpose, the load bank tor) and/or capacitive (lead- serves the power source, using its energy ing power factor) loads. In- output to test, support or protect the power ductive loads, the more com- source. mon type, consist of iron-core A load bank may be permanently installed reactive elements which, when used in conjunction with a re- as an integral component of an electrical generating system or it may be portable, sistive load bank, create a lag- brought into use when needed or applied ging power factor load. Typi- cally, the inductive load will be to several separate systems. rated at a numeric value 75% A resistive load bank, the most common that of the corresponding resistive load such type, proves equivalent loading of both gen- tht when applied together, a resultant 0.8 erator and prime mover. That is, for each power factor load is provided. That is to say, kilowatt (or horsepower) of load applied to for each 100KW of resistive load, 75KVAR of the generator by the load bank, an equal inductive load is provided. Other ratios are amount of load is applied to the prime mover possible to obtain other power factor ratings. by the generator. A resistive load bank, Inductive loads are used to similate real-life therefore, removes energy from the com- mixed commercial loads consisting of light- plete system: load bank from generator— ing, heating, motors, transformers, etc. With generator from prime mover—prime mover a resistive/inductive load bank, full power from fuel. Additional energy is removed as system testing is possible given the impact a consequence of resistive load bank op- of reactive currents on generator/voltage eration: waste heat from coolant, exhaust regulator performance as well as effects on and generator losses and energy consumed conductors and switchgear. by accessory devices. A resistive load bank impacts upon all aspects of a gen- erating system. What is a Load Bank? A capacitive load bank is similar to a reactive load bank in rating and purpose, except lead- ing power factor loads are created. These loads simulate certain electronic or non-linear loads typical of telecommunications, computer or UPS industries. Simplex manufactures a broad line of load banks, including: • Stationary, resistive engine radiator airflow cooled (LBD Series) • Stationary, resistive, resistive/reactive, free- standing forced air cooled (LBS Series) • Stationary, resistive, freestanding, water- Variable power factor loading is possible with a resis- cooled (LBW Series) tive/reactive load bank by adjusting the ratio of resis- tive to inductive load. • Portable, resistive, resistive/reactive, forced air cooled. Automatic • Reverse power/regenerative power protec- Applications tion of generator by sensing power direction • Generator exercise, control from remote con- and magnitude and automatic addition of trol contacts load bank component to act as a power sink. • Automatic exercise/test via programmable microprocessor control Manual • Automatic load leveling/load regulation to • Generator exercise and testing via local or maintain preset load on generator by sens- ing of total load and automatic addition or remote manual control subtraction of load bank component. • Minimum loading of generators Features Malfunction Detection Cooling System Simplex Load Banks are equipped with a mal- Simplex Load Banks are equipped with an inte- function detection system which provides auto- gral forced air cooling system consisting of the matic load disconnect and alarm on sensing of following: an abnormal operating condition. The system • Motor drive propeller fan includes the following: • Fan blade, shrouded for high efficiency • Cooling air intake temperature switch, set at • Motor control contactor 120°F, to sense recirculation of load bank hot exhaust air or an ambient temperature above • Motor circuit breaker the rating of the load bank • Fan motors normally operate at load bank • Cooling air exhaust temperature switch, set line voltage 75°F above maximum rise at maximum am- • Motors for outdoor load banks are totally bient, to sense restricted cooling airflow, re- enclosed circulating air, loss of airflow. • Motors for indoor load banks are open-drip- • Air pressure switch to sense for positive cool- proof ing airflow • Overvoltage, dual/multi-voltage load banks • Automatic load disconnect/lockout circuit • Remote alarm contacts Simplex, Inc. • 1139 North MacArthur Boulevard • Springfield, Illinois 62702 • 217-525-6995 • 24 hr. 217-528-3130 • Fax 217-525-7984 http://www.thomasregister.com/simplexinc • 4A82845 © 1997 • All Rights Reserved • Design subject to change without notice • Printed in the USA What is a Load Bank? Specifications Powr-Web • Alloy: FeCrAl • Maximum continuous temperature Resistive rating: 1920°F Load • Maximum operating temperature as applied in Load Bank: 1080° F Element • Cool down time from operating to ambient temperature is 10 seconds. Description Construction The Simplex “Powr-Web” load resistor is an ad- • Precision calibrated to vanced design, air-cooled power resistor spe- specific ohmic value cifically designed for application to load bank • Welded lugs each end systems. The “Powr-Web” is conservatively op- • All load elements are erated at half the maximum temperature rating continuously supported by of the alloy and features a short-circuit-safe de- vibration resistant, ceramic sign based on continuous mechanical support clad, stainless steel of the resistor by high temperature, ceramic clad throughrods. stainless steel rods. The “Power Webs” are as- sembled into discrete trays which are assembled in a vertical “stack.” Each tray in the “stack” is Ratings independently serviceable without disturbing ad- • 3333W at 120V jacent trays.