Reversible Synchronous Motors

Discussion in 'General Electronics Chat' started by jerseyguy1996, Dec 23, 2013.

  1. jerseyguy1996

    Thread Starter Active Member

    Feb 2, 2008
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  2. MaxHeadRoom

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    Jul 18, 2013
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    I would guess that is a AC stepper motor, as opposed to the identical DC bi-polar pulsed stepper.
    The AC version uses a capacitor to provide a 90° phase shift of the applied frequency for a very accurate synchronous amount of steps/rev. 72rpm on 60Hz.
    Practically instantaneous stop/start and can be stalled without damage to the windings.
    The capacitor is swapped between windings just as a 1ph split phase induction motor is reversed.
    Max.
    .
     
  3. jerseyguy1996

    Thread Starter Active Member

    Feb 2, 2008
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    I think I understand. I have a hard time wrapping my head around the whole capacitor causing a phase shift concept but this gives me a good starting point. Thanks!
     
  4. MaxHeadRoom

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    If you think of two windings fed from the AC but one is in series with a capacitor, in the direct connected winding the current will be in phase with the applied voltage, in the series connected winding, the current will be supplied through the capacitor, in a capacitor, the current leads the voltage, causing a phase difference between the two windings, swap the windings and the direction will change.
    Max.
     
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  5. jerseyguy1996

    Thread Starter Active Member

    Feb 2, 2008
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    That clears it up completely and also tells me why the motor behaved very oddly(but certainly did not turn off like it was supposed to) when I tried controlling it with a relay in between the capacitor and one of the windings. The other winding was still getting power. I need to place the relay at the node before the capacitor. Basically I just need to place the relay on the line from the mains, which is what I should have done from the beginning but I was trying to be fancy about it.
     
  6. MaxHeadRoom

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    If in doubt, follow the instructions! :)
    Max.
     
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