240/ 480 trans sizing - Page 2 - Electrician Talk - Professional Electrical Contractors Forum

brian john · 05-10-2009, 01:17 PM

Quote:

Originally Posted by drsparky

I would get with the husk supplier. They probably have done this many times before. No sense in reinventing the wheel.

STEP ONE...for sure.

wildleg · 05-10-2009, 01:47 PM

actually, I think step one would be to put the horse before the cart. that is to say, what are the loads you want to supply ? you keep saying you want to supply some loads but you haven't described them. do a load calculation for the loads you want to serve, then start figuring out what you can and can't do to serve the loads.

brian john · 05-10-2009, 01:59 PM

Quote:

Originally Posted by wildleg

actually, I think step one would be to put the horse before the cart. that is to say, what are the loads you want to supply ? you keep saying you want to supply some loads but you haven't described them. do a load calculation for the loads you want to serve, then start figuring out what you can and can't do to serve the loads.

Actually to do this you need to know the voltage rating of the equipment which IF at all possible should match the supply voltage. And to do that you should contact the manufacture.

njspark83 · 05-10-2009, 09:44 PM

i agree with wild leg, figure out your calculated load

randomkiller · 05-10-2009, 11:17 PM

Quote:

Originally Posted by brian john

STEP ONE...for sure.

Seconded, it normally helps to start at the beginning.

zgozvrm · 10-23-2009, 03:13 PM

Quote:

Originally Posted by MDShunk

100 kva is 100 kva no matter voltage you step up or down to, and no matter if you give yourself a manufactured phase. 100 kva is still your functional limit.

On the other hand, KVA is calculated differently for single phase and 3 phase. With single phase, you multiply the required current by the voltage you'll be using. For example 240V x 400A = 96,000VA. So 100KVA is used.

Whereas with 3 phase, suppose you needed 240V 3 phase at 400A: The formula now is Volts X Amps X 1.73 (the square root of 3). This results in 240V x 400A x 1.73 = 166,277VA (167KVA is a standard single phase transformer size, but 225KVA is the next larger standard 3 phase size).