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    ghart's Avatar
    ghart Posts: 1, Reputation: 1
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    #1

    Aug 2, 2010, 01:52 PM
    What Size Wire Do I Need to Carry 100 Amps
    If I have 100 amps at 480 what will I have if I transfom it down to 208 three phase?
    lobstertrap's Avatar
    lobstertrap Posts: 20, Reputation: 0
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    #2

    Aug 8, 2010, 10:31 AM

    You needs size 1/0 wire to haul 100 amps.
    lobstertrap's Avatar
    lobstertrap Posts: 20, Reputation: 0
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    #3

    Aug 8, 2010, 10:37 AM

    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)
    tkrussell's Avatar
    tkrussell Posts: 9,659, Reputation: 725
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    #4

    Aug 9, 2010, 05:58 AM
    The following calculations are incorrect.

    Quote Originally Posted by lobstertrap View Post
    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)
    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.
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