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Homework Help: 3 phase 2hp motor current

  1. Nov 22, 2008 #1
    hi there,
    Looking for some info, on how i would find the current draw of a 2 Hp motor running at 208v 3 phase with a unity power factor and efficenty of 100%. I cant seem to put it together today and cannot get ahold of a TA, basically i need to size wires/fuses in a schematic for this current draw and completly forgot how to do this. I keep getting 862 A which i know is way too high. I know 2 hp = 1492 watts. Can someone please help me with the mathematic breakdown? Would be appreciated.

    i think im losing it been a real bad week for me.
    I think can use this:

    P(watts) = I(Amps) * v(volts)

    1492 = I * 208
    I = 7.17 A per phase?

    Is this correct?

  2. jcsd
  3. Nov 22, 2008 #2
  4. Nov 23, 2008 #3


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    This is not my field of expertise, but I am wondering if the 1492 W is the total power, and should be divided up among the 3 phases before doing the "P=IV" calculation?
  5. Nov 23, 2008 #4


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    Your calculation is correct for a single phase motor. For three phase you need to divied by 1.73 (square root of 3).
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