A 100 amp 3 phase power supply is good for how many total amps?

100 amps to a 3 phase load. Power = 100A x Voltage x 1.73 ((line to line voltage)(1.73=SQRT(3)).

173 amps to each of 3 single phase (line to line) loads. Power = 173A x Voltage (line to line voltage).

or... 100 amps to each of 3 single phase (line to neutral) load. Power = 300A x Voltage (line to neutral voltage).

Example:

- 3 phase, 480v, 100amp to a 3 phase heater. 100A x 480V x 1.73 = 83040 watts.

- 3 single phase 480v (L-L voltage) heaters, 100amp. 173A x 480V = 83040 watts.

- 3 single phase 277v (L-N voltage) heaters, 100amp. 300A x 277V = 83100 watts.