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Posted By: Alan McNeil Transformer inrush current - 01/05/01 10:51 PM
Can anyone tell me what the inrush current of a 480/208 75kva transformer would be if it was typically loaded on the secondary side at around 135 amps? I know it goes way high, but I need a ball park figure for argument sake. My boss wants to know why they keep popping the breaker when the transfer switch goes back to normal power. I need a ball park figure
Posted By: Bennie R. Palmer Re: Transformer inrush current - 01/07/01 03:09 AM
Alan: I calculated the maximum inrush current for a 75 KVA transformer as 990 amps.
I do not know the duration. The secondary load is irrelevant for inrush calculations.
A circuit breaker with a time trip curve that will permit 990 amps, with a duration necessary to establish core flux, would be required for starting the transformer.
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