If I have 100 amps at 480 what will I have if I transfom it down to 208 three phase?

You needs size 1/0 wire to haul 100 amps.

you will have 230 amps because 480 volts X 100 amps = 48000 Watts, and divide that by the 208 = 230 amps. (amps X volts = Watts)

The following calculations are incorrect.

Quote:

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Originally Posted by lobstertrap

you will have 230 amps because 480 volts X 100 amps = 48000 Watts, and divide that by the 208 = 230 amps. (amps X volts = Watts)

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When the system is three phase, you must use the constant of the square root of three, 1.73.

Therefore, total power of 100 Amps at 480 Volts 3 phase is:

480 volts x 1.73 x 100 amps = 83,040 Volt Amps.

A 100 Amp load at 480 volts 3 phase would need to be increased by 25%.

So the transformer will need to be at least a 103 KVA unit.

The next size transformer avaialbe is 112.5 Kva.

It can have an output of 312 amps at 120/208 Volts 3 phase.