This is really a simple question for those up on ac theory. However I,m have difficulty getting my head around this problem.
We have a 60KVA 200V 400Hz aircraft GPU. We also used to have a resistive/inductive load bank. We use the 3,4,5 triangle theory for applying the correct load @ 0.8PF ie 36KVAR (3 reactive load) + 48KW (4 resistive) = (5)60KVA. Interms of amps per phase it equates to (60000/115)/3 = 174Amps. We never had a problem with this method.
However our resistive/inductive load bank has been withdrawn from service. We now have a purely resistive load bank with the load selector dials marked in KW.
OK what our people are doing now is selecting 48KW on the load bank of which they believe is full load. I know the full load current for a60KVA (48KW) machine is 174A, but selecting 48KW is about 140A per phase. This in my opinion is NOT full load.
Here is the strange thing, if i input 60KW on the load bank the line currents are 174A. bank on!
So am i correct in saying that at unity power factor KW=KVA? Should the manufacturers of the load bank have marked up the input dial in KVA instead of KW?
Can anyone put the math in simple terms or correct my theory?