Stallcup's and transformer OCPD calcs?

[Poolside]

In "Stallcup's Generator, Transformer, Motor, and Compressor" book, (Chap. 11) there are examples given for determining the OCPD for the primary.

This is the example:

Given: 500kVA @ 4160V

FLA= kVA x 1000 / V x 1.73
FLA= 500 x 1000/ 4160 x 1.73
FLA= 69.4

The math doesn't work out. The FLA that is listed is 1/3 of the calculated result. Is there a step missing from his example here?

- Greg

 

[coulter]

...The math doesn't work out. The FLA that is listed is 1/3 of the calculated result. Is there a step missing from his example here? ...

Maybe, try this: FLA= 500 x 1000/ (4160 x 1.73)

carl

 

[Poolside]

Yeah. Got it. That was it. The order of operations needs to have parenthesis.

It's that attention to detail thing...


- Greg