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Rotation direction of an ac induction motor

  1. Nov 2, 2009 #1
    I want to know that is the direction of a single phase or three phase ac induction motor is fixed and it is clockwise? ...or it may be both anti-clockwise and clockwise..or it can be both directional for single phase and only clockwise directional for 3 phase?.....thanks
  2. jcsd
  3. Nov 2, 2009 #2
    Single phase motors can run either way,depending on how the starting circuit (capacitor start, split phase start, etc.) is wired.
    Three phase motors can run either way depending on how the 3 phases are connected to the motor. I have seen vacuun pumps on large vacuum systems run backwards, because someone forgot how to wire up the motor phases.

    Bob S
  4. Nov 2, 2009 #3
    Some motors are designed so that the user can change the direction with a switch.
  5. Nov 2, 2009 #4


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    Yes and just switch two phases and it will run in the opposite direction.
  6. Nov 3, 2009 #5
    thanks... I got my answer
  7. Nov 3, 2009 #6


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    We did that once (cryopump compressor). It made a hell of a racket for the few seconds it was up while we were trying to figure out if that was the normal sound or not (though to be fair, the documentation just told us to hook it up, and switch two leads if we didn't think it was running properly).
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