Amperage change from 480v to 120v and from three phase to single

You are very confused. Are you sure you are qualified to be doing this?

conboy 24000 watts divided by 120 volts equals 200 amps single phase, you would want a 480 volt 3 phase to 120/208 volt step down transformer to get your 120 volt single phase, lets see if you can figure out the rest of the story? good luck. pac

This is so vital to get right (and expensive and possibly dangerous if you get it wrong!!), what the hell are you doing?

Its totally outside of your knowledge and training by the sound of it!!

And to start asking on the Internet is really very, very stupid. Your one and only Brain Cell must get very lonely some days.....

Get a professional that KNOWS!!!

Brian, we are not sure what your set-up really looks like. But, true, when you step voltage down through a transformer it steps current up. Excluding losses in the transformer, power in = power out. An electrical supply house in your area can give you the specs on your transformer and explain what you have. I'm sure a contractor is designing the system and you are wanting to stay knowlegable. E-mail me if you want to keep a lower profile. The woods are full of snipers.

James

With tranformers it's all about ratio. The ratio of 480V to 120V is 4:1. As voltage goes down current goes up proportionally, so if you have a 4:1 voltage ratio, your current ratio is opposite at 1:4. If you have 90A on the secondary, the primary current would 22.5A, or 1/4th.

Your formula is whacked.

What I see here is a 90A. @ 3 Ph. 480 into a 3 Ph.UPS,
(~75 KVA Input Cap.), with 66.8A. (~55.5 KVA Output Cap.), Eff.= 75%.
This suggests that your UPS will produce an additional 20K BTUs for
you to deal with just for the 24KW of 120V. power.
(If there are other loads at 480V, you have to consider the additional
losses for them in your 'UPS" heat gain figure.
If not, why so large a unit if you only require 24KW. of power?)
I'd suggest a 3 Ph. 120/208V. transformer and distribution panel
for your power supplies, 30KVA T/F, 100A. Pnl. & Wiring.

The amperes out of the UPS are only indirectly related to the input amps.

The output will be limited by nominal step down transformer and rectifier losses, battery efficiency issues, inverter losses, and discharge limitations. The battery discharge rate will be limited to some many amp-hours per hour to a load and the ups can not usually exceed a depth of discharge greater than 50% of the bank's capacity.

You got 8000 Watt-hours of bank. Your bank at 24,000 Watts would last about 20 minutes. The fast discharge rate would lower this time frame even further.