Transformer Calculations

[Gary11734]

The customer has purchased a 112.5kva transformer. We have 200 amps 3phase 240v available on the primary and we want to feed a 100 amp 480v 3 phase secondary panel. It seems to me the 112.5kva is a little large for the 200 amp circuit breaker. I am rusty on calculations. Will this set up work? :?

Here's a question?

If the owner could only buy a 225 KVA transformer for this application, could you use the ampacity size you have in the question and still meet code?

 

[dmsv10]

Okay this thread might be getting a little old or redundant but when you say you have three phase 240 volt on your primary and you want to feed a 3-phase 480 volt load how do you obtain that or am I missing some information

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[kwired]

Okay this thread might be getting a little old or redundant but when you say you have three phase 240 volt on your primary and you want to feed a 3-phase 480 volt load how do you obtain that or am I missing some information

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Um, with the transformer that the discussion is mostly about?

 

[laketime]

What's the load is the question...

The load in question is small. (2) 5 amp cranes and (1) welder used intermittely.

 

[laketime]

So customer just sent me a link saying they bought a transformer, without talking to me, that has a primary of 480v 3 phase and secondary of 208v 3 phase. Can I feel that secondary side with 240v 3 phase and still get 480v on the primary side, keep in mind feeding this backwards. Doesnt seem to me it would work but I am not good in this area.

 

[gar]

181228-1449 EST

Quite obviously not.

240 V on a 208 winding will severely saturate the core. And that most likely is not the only problem.

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