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Phase to Phase fault?

  1. Mar 16, 2009 #1
    In a 480v Three Phase Induction Motor.....what kind of educated guess or assumption can be made as a cause, when two of the three fuses blow? Is there any type of significance in two fuses blowing instead of just one in a three phase motor circuit?

    If only one fuse blew it basically would mean there was a phase to earth fault,
    what about two?.....phase to phase, im thinking?
  2. jcsd
  3. Mar 16, 2009 #2
    If a 3 phase motor is overloaded, something will have to give first. So, suppose fuse #1 blows. Ok, no problem, but now we are feeding an already overloaded 3 phase motor with only 2 phases. So, much current is drawn, and another fuse blows. Now there is only one phase left and no longer a return path since any 3 phase motor I've ever seen does not use a 4th conductor to actually carry any current. So there is your answer. Probably doesn't help you much.
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