Sizing OCP for Transformer

[welectrical]

I've always been confused on transformer sizing because it seems like both the primary and secondary are getting oversized.

If I have a 112.5kVA 480:208V 3P transformer, can (should) I size the OCPs as follows:

primary 200A, 480V, 3P
secondary 400A, 480V, 3P
i would match the wire sizes to the ampacity on each side

 

[ron]

First figure out the full load amps, then use the table for maximum breaker sizes 450.3(B).
200A for the primary is reasonable.
400A for the secondary is fine (considering Note 1 to the table)

 

[infinity]

200/400 is pretty standard.

 

[jap]

175/400 is even more common.

JAP>