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Reversing motor

Discussion in 'Electronic Basics' started by Mike G, Jan 17, 2004.

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  1. Mike G

    Mike G Guest

    Hello all. Hope you can help me.

    My dishwasher washing pump seized, so i managed to rob a water pump from and
    old washing machine i had laying around. The plastic pump end was similar
    size so i was able to swap it (hence all the hoses fitted). However, the
    volute casing requires the pump to run in a particular direction. The motor
    from the washing machine runs in the opposite direction.

    The motor is supplied by two wires, a live and neutral (mains). I have tried
    swapping them over, but it still runs in the wrong direction to want i want
    it to!

    Is there any way I can reverse the direction of the motor??
    (The motor does not have brushes, from what i can see.)

    Many thanks.

  2. Thinker

    Thinker Guest

    Some of these small motors are similar on both ends except for the shaft. If
    that is the case sometimes you can reverse the shaft and end assmblies so
    shaft projects from the opposite end of the windings. This will reverse the
    rotation. Some are built for one direction only and are very difficult to
  3. Don Bruder

    Don Bruder Guest

    MOST of the small ones are built unidirectional, and are not only
    difficult, but may very well be outright impossible to reverse. (Barring
    insane attempts like a complete disassembly/rewire/reassembly, and even
    that isn't guaranteed)

    You want a reversible motor, you're going to have to get one
    specifically set up for it if you don't want a major headache. Trying to
    reverse an existing fractional-horsepower motor that wasn't originally
    designed as bi-directional is more nightmare than it's likely to be
    worth. *IF* you're lucky enough to have one where it's even *POSSIBLE*.
  4. Eric R Snow

    Eric R Snow Guest

    It may be possible. Really depends on what kind of motor. Does it have
    a centrifigul start switch? This switch can be heard clicking
    sometimes when the motor starts and stops. When started it will click
    when the motor is almost up to speed. And when power is removed you
    can hear it click after the motor has slowed down a bit. This switch
    is located on the motor shaft itself. That kind of motor may be
    reversible. Some capacitor start motors are also reversible. So try to
    identify this motor.
  5. Mike G

    Mike G Guest

    I've managed to disassemble it a bit. Unfortunately, the shaft is longer on
    one end, so i can't just swap the impeller onto the other side.

    I've noticed that a small metal component (capacitor?) is wired in series
    from the live terminal, before the winding. The neutral winding ends
    straight at the connection. I wonder now, if I change that component so that
    its in series on the neutral side, if this would reverse the motor?

    Any help, greatly appreciated.

  6. Nick Hull

    Nick Hull Guest

    The volute casing is optomized for a particular rotation. Centrifugal
    pumps will work with either rotation, less efficient the 'wrong' way.
    Have you tried it to se if it works?
  7. Don Kelly

    Don Kelly Guest

    No. What you want to do is switch the part of the winding that is in series
    with the capacitor or the other part of the winding .
    You will likely have something like this
    -------------/ ----||-----winding-----
    | switch |
    main winding |
    __ |________________________|
    The switch is a centrifugal switch which opens when the motor is up to speed
    (may not be there)
    The top winding is the start winding and the || is the capacitor.
    To reverse, reverse either the top winding or the main winding, not both.
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