AC permanent magnet motor

Discussion in 'General Electronics Chat' started by drufft, Feb 21, 2013.

  1. drufft

    Thread Starter New Member

    Feb 21, 2013
    4
    0
    Hello,
    I'm a power systems engineer at a coal preparation plant. I work on AC and DC systems all the time. Naturally my sister stumped me with a Christmas display. Basically, it drags a little train around in a circle via magnetics. This year the motor ran backwards and the train is not set up to do that, it slides off the display. The motor is a tiny,universal 12vac with CCW written on it. The case came apart okay yielding a bunch of gearing a coil wound on a plastic hoop and a driven magnet glued to the rotor shaft. First, how does that work. Shouldn't the pulsing AC waveform simply vibrate the magnet. Second, can I reverse direction. It looks like it's going in the nameplate direction but my OLDER sister say NO WAY.

    Thanx

    Dave
     
  2. BillB3857

    Senior Member

    Feb 28, 2009
    2,400
    348
    A picture would help.
     
  3. DerStrom8

    Well-Known Member

    Feb 20, 2011
    2,428
    1,328
    Hi there Dave. Welcome to AllAboutCircuits!

    As Bill suggested, a photo would be very helpful. I don't really understand how this is set up. :p
    Thanks,
    Matt
     
  4. drufft

    Thread Starter New Member

    Feb 21, 2013
    4
    0
    Whoops, got it. Sketch of overall setup. Can follow with motor drawing?
     
    Last edited: Feb 21, 2013
  5. bertus

    Administrator

    Apr 5, 2008
    15,638
    2,343
    Hello,

    In this part of the FAQ is written how to attach files and pictures:
    Attachments and Images

    Bertus
     
  6. drufft

    Thread Starter New Member

    Feb 21, 2013
    4
    0
    I have attached a drawing of the motor, now that I now how.
     
  7. DerStrom8

    Well-Known Member

    Feb 20, 2011
    2,428
    1,328
    Ah, I understand now.

    AC motors are designed so that the AC actually causes the motor to turn in one direction, rather than vibrate. You can look up how an AC motor works to understand why.

    I assume the reason the train slides off is because the magnet on the train (attracted to the arm) is seated at the front, so when it moves in that direction, the rest of the train follows the front part. I am not sure if you want the train to move backwards, or just go forwards in the opposite direction. Either way it's possible, though if you want the train to move backwards, you'd need to put the magnet at the back of the train instead of the front.

    A photo would still be helpful, since the diagram doesn't show exactly how it's set up.

    Also, the reason a motor might turn backwards is if the power leads are on backwards or the polarity was changed by some other means. I see no reason why it would just switch direction randomly, unless the gearing is messed up.

    Regards,
    Matt
     
  8. drufft

    Thread Starter New Member

    Feb 21, 2013
    4
    0
    Usually with larger ac motors, you have a start coil and run coil. Switching polarity of either, but not both, will reverse. I tried swapping the two power leads. No luck. The train itself has wheels with axles cut left so that it rolls correctly in only one direction. I'm more interested in how that little motor runs. I will research that some more. Thanks, I'll get back when I learn some more. I appreciate the help. I've been a lurker on forums for a while and will be retiring soon. May spend some time trying to be helpful myself.

    Dave
    Dave
     
Loading...