The load bank develops an electrical load, applies the load to an electrical power source, and converts or dissipates the resultant power output of the source. The load bank should mimic the operational or “real” load which 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. A load bank can be further defined as a self-contained, unitized, systematic device which includes both load elements with control and accessory devices required for operation.
Where 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 with Engine Generators, Battery Systems, UPS Systems, Inverters, Ground Power Units, Auxiliary Power Units, Aircraft Power Generators, Wind Generators, and Hydro Generators. Load Banks can be used for several purposes:
Manufacturing Testing
- Generator Test Cells: Manufacturers of standby power generators commonly use load banks to test and tune newly assembled units. When the generator has been set up in a test cell within the factory, a test engineer uses the load bank to apply a discrete, selectable electrical load to the generator and measure the response stability and endurance. During this process, the test engineer calibrates and adjusts the generator performance to ensure it meets the intended product specifications and tolerances.
- Engine Test Cells: Manufacturers of small gas engines also use load banks to test newly manufactured engines under various mechanical loads. This is accomplished by connecting the engine to the load bank via a device called a dynamometer. Again, engine performance is monitored and, if necessary, adjustments are made to ensure the product performs within intended specifications.
Field Testing & Exercise
Generators installed in the field must be periodically tested and exercised to ensure that it will operate as intended when a power outage actually occurs. Service groups use load banks to apply a load that mimics the load of the facility the generator is protecting. Any problems with the generator can then be identified and rectified in a non-critical environment.
Elimination of ‘Wet Stacking’
Load banks may be installed in a diesel powered generator set to apply the additional load required to ensure the engine fully consumes the fuel in the combustion process. If a diesel engine is not operated under adequate load, unconsumed fuel will collect in the engine’s exhaust stack, causing “wet stacking” problems.
Demonstration
Load banks are often used as a tool for demonstrating to buyers and users of a new generator set that the unit meets the performance specifications outlined in the purchase contract.
And More – Load banks are also used for:
- UPS system testing
- Battery system testing
- Ground power testing
- Load optimization in prime power applications
- Factory testing of turbines
There are three types of load banks — resistive, reactive, and resistive/reactive:
Resistive
A Resistive load bank, the most common type, proves equivalent loading of both generator and prime mover. For each kilowatt (or horsepower) of load applied to the generator by the load bank, an equal amount of load applies 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 because of resistive load bank operation: waste heat from coolant, exhaust and generator losses and energy consumed by accessory devices. A resistive load bank impacts all aspects of a generating system.
The “load” of a resistive load bank is created by the conversion of electrical energy to heat by power resistors. This heat must be dissipated from the load bank, either by air or by water, by forced means or convection.
In a testing system, a resistive load simulates real-life resistive loads, such as lighting and heating loads and the resistive or unity power factor component of magnetic (motors, transformers) loads.
Resistive load banks can be further divided into these categories:
- DC Portable: A resistive load bank easily carried or pushed on wheels for testing and maintaining DC power equipment such as battery chargers, battery systems, UPS systems, and DC generators.
- AC Small Portable: A resistive load bank easily carried or pushed on wheels for testing and maintaining AC power equipment such as UPS systems and generators up to 150 kW.
- AC Large Portable: A resistive load bank on wheels for testing and maintaining larger AC power equipment such as UPS systems and generators up to 1000 kW.
- AC Trailer Mounted: A resistive load bank loaded on a trailer for testing and maintaining AC power equipment such as UPS systems and generators at different sites up to 3000 kW.
- AC Stationary: A resistive load bank for testing and maintaining AC power equipment such as UPS systems and generators at one location up to 4600 kW. Many models can modular building blocks for applications requiring a capacity of tens or hundreds of megawatts.
- AC Medium/High Voltage: A resistive load bank for testing and maintaining larger generators and other AC power equipment up to 7000 kW and up to 15,000 volts.
- AC Radiator Cooled: A resistive load bank for testing and maintaining AC power equipment utilizing the radiator air outflow of a generator engine to cool the resistive load elements. These load banks can be adapted to fit varying site conditions and duct dimensions. Available up to 1200 kW.
- AC Water-Cooled: A resistive load bank for testing and maintaining AC power equipment utilizing water instead of air for cooling the resistive load elements. Perfect for environments requiring super-quiet operation. Available up to 2500 kW.
Reactive
A “reactive” load includes inductive (lagging power factor) and/or capacitive (leading power factor) loads.
Inductive
Inductive loads, the more common type, comprise iron-core reactive elements which, when used 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. For each 100KW of resistive load, 75KVAR of inductive load is provided. These reactive load banks are available up to 1875 kVAR.
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 given the impact of reactive currents on generator/voltage regulator performance, as well as effects on conductors and switchgear.
Capacitive
A capacitive load bank is like a reactive load bank in rating and purpose, except that leading power factor loads are created. These loads simulate certain electronic or non-linear loads typical of telecommunications, computer or UPS industries. These capacitive load banks are available up to 2000 kVAR.
Resistive/Reactive Load Banks
Resistive/reactive load banks combine both resistive and reactive elements in one load bank package up to 6250 kVA.
If you have further questions, or would like help to select a load bank for your specific application, please call us at 1-888-331-5344.
For a price quote on load banks, please call, fax or e-mail us:
Call: 1-888-331-5344
Fax: 1-616-452-1337
E-mail: customerservice@steadypower.com
In order to give you an accurate price quote, we will need the following information:
- Name, Title, Company, Phone, Fax, E-mail
- Shipping Address with Zip Code (for shipping cost)
- Manufacturer and Model (if known)
- Form: Portable, Trailer-Mounted, Stationary, Radiator
- Enclosure: Indoor (Type 1) or outdoor (Type 3R)
- Type: Resistive only, Reactive only, Resistive/Reactive
- Total Capacity: kW rating
- Voltage, AC or DC, Phase, Frequency, Power Factor
- Load step resolution (minimum load step size required)
- Local or remote control panel
- Automatic load regulating or manual control
- Any additional information or options desired
- Is there a specification you are working from? If so, can you send?
- Component panel side (Radiator-cooled only)
- Mounting requirements–feet, flange, etc. (Radiator-cooled only)
