Load Bank Basics
This article covers load bank basics such as what it is, how it works and what it does.
Load banks are used to commission, maintain, and verify electrical power sources such as diesel generators and uninterruptible power supplies (UPS). The load bank applies an electrical load to the power source and dissipates the resulting electrical energy through resistive elements as heat. The resistive elements are cooled with motorised fans within the load bank construction. Load banks can either be permanently installed at a facility and permanently connected to a power source or portable versions can be used for testing when required.
Load banks are the best way to replicate, prove and verify the real-life demands on critical power systems.
Resistive Load Banks
A resistive load bank can be used to fully test the generator set at 100% nameplate kW rating. It will also fully load the generator cooling, fuel, and exhaust systems. Only 80% of the generator set nameplate kVA rating can be achieved when utilizing a resistive unit. The resistive load bank will provide a unity or 1 power factor (PF) load to the system under test. Resistive units are predominantly used for AC voltages, however specifically designed DC load banks are also available.
Inductive Load Banks
An inductive load bank is normally used in conjunction with a resistive unit to provide a lagging power factor load test. This provides the capability to test the generator set fully at 100% nameplate kVA rating. Inductive load banks add inductance to the load and therefore reduce the PF to less than unity (typically 0.8pf on diesel gen-set). Inductive load banks are rated in kilovolt-amperes reactive (kVAr).
Capacitive Load Banks
A capacitive load bank is normally used in conjunction with a resistive unit to provide a leading power factor load test. Capacitive load banks incorporate industrial capacitors and increase the PF to above unity (leading). Capacitive load banks are rated in kilovolt-amperes reactive (kVAr).
Resistive Reactive (Combined) Load Banks
A resistive reactive load bank usually consists of both resistive elements and inductors that can be used to provide load testing at non-unity PF (lagging) including the capability to test the generator set fully at 100% nameplate kVA rating. Combined load banks incorporate resistors and inductors all in a single construction which can be independently switched to allow resistive only, inductive only, or varying lagging power factor testing. Combined load banks are rated in kilovolt-amperes (kVA). It’s worth noting that combined load banks can consist of resistive, inductive, and capacitive (RLC) also.
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