Circuit Breaker size

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stevewill

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I need to Install a large power supply.
Input = 480Vac, 200A, 3p.
Output = 0-125Vdc, 0-300 A, 37.5KW.
How do I determine the size of breaker and wire to feed this power supply from a panel?
Thanks for any help!!
 
Re: Circuit Breaker size

If it is possible for the supply to run full out for 3 hours or more, then

200A *1.25
for the size of the breaker and ampacity of the wire.

[ February 05, 2004, 02:29 PM: Message edited by: ron ]
 
Re: Circuit Breaker size

The voltage under consideration is DC therfore a breaker of 300Ampere is adequate for the load current mentioned by you. As for the feeder size,it will depend on many factor like length, temperature, type of lay etc.
 
Re: Circuit Breaker size

Originally posted by pasha:
The voltage under consideration is DC therfore a breaker of 300Ampere is adequate for the load current mentioned by you. As for the feeder size,it will depend on many factor like length, temperature, type of lay etc.
Click to expand...
Pasha can you elaborate on your post, I do not understand what you mean by "lay".

Also while he was talking about a DC supply he was asking about the feeder breaker with a input current of 200 amps.

This says to me a 200 amp breaker if non-continuous or 250 amps if continuous.

A 300 amp breaker would be the maximum size breaker allowed is it not? 422.11(E)
 
Re: Circuit Breaker size

Mr.Iwire, You are right, its me who missunderstood the question. Thanks for the advice.
 
Re: Circuit Breaker size

Input: 200A at 3ph, 480 = 166 KVA. Output: 125VDC x 300A = 37.5 KVA. This just does not sound right, or it makes a lot of heat!
 
Re: Circuit Breaker size

Nvcape
There is always a high loss across a AC to DC power supply and the fact that it has varible voltage and current output adds to the loss even more. yes there will be alot of heat LOL :p

I'll bet you thought this was a transformer. LOL :p

[ February 23, 2004, 09:47 PM: Message edited by: hurk27 ]
 
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