Load banks carry ratings for voltage, power, frequency, and other parameters. Using load banks where parameters differ from rated values makes them useful in a wider range of circumstances, but requires users to understand how circuit characteristics impact their maximum capacity. This article provides guidance for de-rating load banks accordingly.

De-Rating Maximum Capacity for Actual Circuit Voltage

Load banks should never be operated above their maximum rated voltage, but can be used for testing at lower voltages. Doing so, however, will affect the maximum amount of load a unit can apply according to the following formula:

[(Applied Voltage)2/(Rated Voltage)2] x Rated Capacity

The maximum load that a 400-kilowatt 240-volt load bank could apply to a 208-volt circuit would thus be calculated as follows:

[(208 V)2/(240 V)2] x 400 kW = 300 kW