fault current for MCB on secondary of 75 KVA transformer

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Can I use Mike's fault current program to calculate the AIC for a 200A main breaker on the 208v secondary side of a 75 KVA 480v-208v transformer?

I know the fault current of the 75kva transformer, as well as the length and type of feeders from the transformer to the main breaker? The 100A breaker on the primary side is rated @ 30KAIC.

I used the program for the secondary, and it came out less than 10KAIC, which makes sense to me.

Want to check with the experts first.

Thanks in advance
 

kwired

Electron manager
Location
NE Nebraska
The 30k primary side breaker may need to be that high because of the available current from the primary source.

The transformer impedance will limit how much current can flow in the secondary circuit, as Ron said even a low impedance unit for that size would not allow for more then 10k to flow which makes the 30k primary kind of meaningless to your secondary available fault current.
 
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