Can we apply 208V to a 480V/240V the Loadbank and make it functional using the internal power for the controls and blowers? What is the resulting kW rating?

Applying 208V to a 480V/240V-rated portable/trailer-mounted load bank is generally considered allowable. The reason for this is that the blower motors installed on these loadbanks are typically rated for 208-230/460V.

A. Affected units:
Portable Loadbanks with 480V/240V selection ONLY
Trailer-mounted Loadbanks with 480V/240V selection ONLY

B. Points to consider
The voltage selector needs to be set to 240V
The 208V source frequency needs to match the rated frequency of the loadbank for proper blower motor speed and hence, the proper airflow rate for cooling.

C. Calculation of de-rating with an example:
If the loadbank is rated 500kW at 208V/480V, the derated capacity at 208V is 375kW per the following formula.