A
load bank is a device which develops an
electrical loadIf an electric circuit has a well-defined output terminal, the circuit connected to this terminal is the load....
, applies the load to an electrical power source and converts or dissipates the resultant power output of the source.
The purpose of a load bank is to accurately mimic the operational or “real” load that a power source will see in actual application. However, unlike the “real” load, which is likely to be dispersed, unpredictable and random in value, a load bank provides a contained, organized and fully controllable load.
Consequently, a load bank can be further defined as a self-contained, unitized, systematic device that includes load elements with control and accessory devices required for operation.
Whereas the “real” load is served by the power source and uses the energy output of the source for some productive purpose, the load bank serves the power source, using its energy output to test, support or protect the power source.
Load banks are used in a variety of applications, including:
- Factory testing of turbine
A turbine is a rotary engine that extracts energy from a fluid or air flow and converts it into useful work.The simplest turbines have one moving part, a rotor assembly, which is a shaft or drum, with blades attached. Moving fluid acts on the blades, or the blades react to the flow, so that they...
s and engine diesel generatorA diesel generator is the combination of a diesel engine with an electrical generator to generate electric energy. Diesel generating sets are used in places without connection to the power grid or as emergency power-supply if the grid fails...
sets
- Reduction of wet stacking
Wet stacking is a condition in diesel engines in which all the fuel is not burned and passes on into the exhaust side of the turbocharger and on into the exhaust system....
problems
- Periodic exercising of stand-by engine generator sets
- Battery
An electrical battery is a combination of one or more electrochemical cells, used to convert stored chemical energy into electrical energy. Since the invention of the first Voltaic pile in 1800 by Alessandro Volta, the battery has become a common power source for many household and industrial...
and UPS systemAn Uninterruptible power supply , also known as a battery backup, provides emergency power and, depending on the topology, line regulation as well to connected equipment by supplying power from a separate source when utility power is not available...
testing
- Ground power testing
- Load optimization in prime power applications
- Removal of carbon build-up on piston
A piston is a component of reciprocating engines, pumps and gas compressors. It is located in a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from expanding gas in the cylinder to the crankshaft via a piston rod and/or connecting rod...
heads
The three most common types of load banks are resistive load banks, reactive load banks, and capacitive load banks.
A resistive load bank, the most common type, provides equivalent loading for both
generatorIn electricity generation, an electrical generator is a device that converts mechanical energy to electrical energy. The reverse conversion of electrical energy into mechanical energy is done by a motor; motors and generators have many similarities...
s and prime movers.
A
load bank is a device which develops an
electrical loadIf an electric circuit has a well-defined output terminal, the circuit connected to this terminal is the load....
, applies the load to an electrical power source and converts or dissipates the resultant power output of the source.
The purpose of a load bank is to accurately mimic the operational or “real” load that a power source will see in actual application. However, unlike the “real” load, which is likely to be dispersed, unpredictable and random in value, a load bank provides a contained, organized and fully controllable load.
Consequently, a load bank can be further defined as a self-contained, unitized, systematic device that includes load elements with control and accessory devices required for operation.
Whereas the “real” load is served by the power source and uses the energy output of the source for some productive purpose, the load bank serves the power source, using its energy output to test, support or protect the power source.
Applications
Load banks are used in a variety of applications, including:
- Factory testing of turbine
A turbine is a rotary engine that extracts energy from a fluid or air flow and converts it into useful work.The simplest turbines have one moving part, a rotor assembly, which is a shaft or drum, with blades attached. Moving fluid acts on the blades, or the blades react to the flow, so that they...
s and engine diesel generatorA diesel generator is the combination of a diesel engine with an electrical generator to generate electric energy. Diesel generating sets are used in places without connection to the power grid or as emergency power-supply if the grid fails...
sets
- Reduction of wet stacking
Wet stacking is a condition in diesel engines in which all the fuel is not burned and passes on into the exhaust side of the turbocharger and on into the exhaust system....
problems
- Periodic exercising of stand-by engine generator sets
- Battery
An electrical battery is a combination of one or more electrochemical cells, used to convert stored chemical energy into electrical energy. Since the invention of the first Voltaic pile in 1800 by Alessandro Volta, the battery has become a common power source for many household and industrial...
and UPS systemAn Uninterruptible power supply , also known as a battery backup, provides emergency power and, depending on the topology, line regulation as well to connected equipment by supplying power from a separate source when utility power is not available...
testing
- Ground power testing
- Load optimization in prime power applications
- Removal of carbon build-up on piston
A piston is a component of reciprocating engines, pumps and gas compressors. It is located in a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from expanding gas in the cylinder to the crankshaft via a piston rod and/or connecting rod...
heads
Types of load bank
The three most common types of load banks are resistive load banks, reactive load banks, and capacitive load banks.
Resistive load bank
A resistive load bank, the most common type, provides equivalent loading for both
generatorIn electricity generation, an electrical generator is a device that converts mechanical energy to electrical energy. The reverse conversion of electrical energy into mechanical energy is done by a motor; motors and generators have many similarities...
s and prime movers. That is, for each kilowatt (or
horsepowerHorsepower is the name of several non-SI units of power. It was originally defined to allow the output of steam engines to be measured and compared with the power output of draft horses. The horsepower was widely adopted to measure the output of piston engines, turbines, electric motors and other...
) of load applied to the generator by the load bank, an equal amount of load is applied to the prime mover by the generator. A resistive load bank, therefore, removes energy from the complete system: load bank from generator—generator from prime mover—prime mover from fuel. Additional energy is removed as a consequence of resistive load bank operation: waste heat from coolant, exhaust and generator losses and energy consumed by accessory devices. A resistive load bank impacts upon all aspects of a generating system.
The “load” of a resistive load bank is created by the conversion of electrical energy to heat via high-current resistors such as grid resistors. This heat must be dissipated from the load bank, either by air or by water, by forced means or
convectionConvection is the movement of molecules within fluids . Convection is one of the major modes of heat transfer and mass transfer...
.
In a testing system, a resistive load simulates real-life resistive loads, such as
incandescent lightingThe incandescent light bulb, incandescent lamp or incandescent light globe is a source of electric light that works by incandescence . An electric current passes through a thin filament, heating it until it produces light...
and heating loads as well as the resistive or unity
power factorThe power factor of an AC electric power system is defined as the ratio of the real power flowing to the load to the apparent power, and is a number between 0 and 1 . Real power is the capacity of the circuit for performing work in a particular time. Apparent power is the product of the current and...
component of magnetic (motors, transformers) loads.
The most common type utilises wire resistance, usually with fan cooling and these are often portable and moved from generator to generator for test purposes. Sometimes they are built into the building but this is unusual.
Sometimes, though rarely now, a
Salt water rheostatA salt water rheostat is a tank containing brine in which electrodes are submerged to create an electrical load. The electrodes may be raised or lowered into the liquid to respectively decrease or increase the resistive of the load. To stabilize the load, the mixture must not be allowed to boil...
is employed. These are sometimes still resorted to in remote locations since they can be readily improvised.
Reactive load bank
A “reactive” load includes inductive (lagging
power factorThe power factor of an AC electric power system is defined as the ratio of the real power flowing to the load to the apparent power, and is a number between 0 and 1 . Real power is the capacity of the circuit for performing work in a particular time. Apparent power is the product of the current and...
) and/or capacitive (leading power factor) loads.
Inductive loads, the more common type, consist of iron-core reactive elements which, when used in conjunction with a resistive load bank, create a lagging power factor load. Typically, the inductive load will be rated at a numeric value 75% that of the corresponding resistive load such that when applied together a resultant 0.8 power factor load is provided. That is to say, for each 100 kW of resistive load, 75 kvar of inductive load is provided. Other ratios are possible to obtain other power factor ratings. Inductive loads are used to simulate real-life mixed commercial loads consisting of lighting, heating, motors, transformers, etc. With a resistive/inductive load bank, full power system testing is possible, showing the impact of reactive currents on generator/voltage regulator performance as well as effects on conductors and switchgear.
Capacitive load bank
A capacitive load bank is similar to a reactive load bank in rating and purpose, except leading power factor loads are created. These loads simulate certain electronic or non-linear loads typical of telecommunications, computer or UPS industries.
Electronic load bank
An electronic load bank tends to be a fully programmable, air- or water-cooled design used to simulate a solid state load, and to provide constant power and current loading on circuits for precision testing.
Railways
Where a diesel-electric locomotive is equipped for
dynamic brakingDynamic braking is the use of the electric traction motors of a railroad vehicle as generators when slowing the vehicle. It is termed rheostatic if the generated electrical power is dissipated as heat in brake grid resistors and regenerative if the power is returned to the supply line...
, the braking resistor may be used as a load bank for testing the engine-generator set.
See also
- Dummy load
A dummy load is a device used to simulate an electrical load, usually for testing purposes.- Radio :In radio this device is also known as a dummy antenna or a radio frequency termination. It is a device used in place of an antenna to aid in testing a radio transmitter...
- Salt water rheostat
A salt water rheostat is a tank containing brine in which electrodes are submerged to create an electrical load. The electrodes may be raised or lowered into the liquid to respectively decrease or increase the resistive of the load. To stabilize the load, the mixture must not be allowed to boil...
- Relative cost of electricity generated by different sources
- Relative cost of electricity by generation source :Politicians, academics and commentators are often tempted to generalize about the relative costs of electricity from different sources. In practice, there is no such thing as a representative cost of production from a particular technology....
- Diesel-electric transmission
- Motor-generator
A motor-generator is a device for converting electrical power to another form. In some contexts, the other form is mechanical energy; in other contexts, it is a different form of electricity. The two senses refer to different types of equipment.The Motor-generator set is used to convert...
- Three-phase electric power
Three-phase electric power is a common method of alternating-current electric power transmission. It is a type of polyphase system, and is the most common method used by electric power distribution grids worldwide to distribute power. It is also used to power large motors and other large loads...
- Wet stacking
Wet stacking is a condition in diesel engines in which all the fuel is not burned and passes on into the exhaust side of the turbocharger and on into the exhaust system....
External links