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Broken ceiling fan

Discussion in 'Electronic Design' started by martin.shoebridge, Aug 7, 2006.

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  1. It's a synchronous 240v ac fan . There's a 1.5uF 450V cap inside, a
    fwd/reverse switch and a 3 speed switch. When I turn it on, it hums
    slightly. It won't go even if I spin the rotor. Is the most likely fault the
    cap? The fan lasted 2 days before failing. I can't get inside the motor to
    see if there's anything else that could be faulty.
    Any clues?
  2. "The fan lasted 2 days before failing"

    take it back then, get another one

  3. Yes, the cap is a prime suspect. Take the fan back under guarantee.
  4. Rich Grise

    Rich Grise Guest

    I concur with the others - it's broken, take it back.

    But, if it didn't even spin after you "helped" it, then it's not the
    capacitor. We did this experiment in High School Physics last century,
    and if the windings of an induction motor are intact, it _will_ spin
    without the cap - it's just that it has to be hand-started, and the
    rotor has to catch up with the reversals of the magnetic field.

  5. That worked for your motor but it doesn't necessarily work for all
    modern motors. No, I don't know why.
  6. It might not work for a high RPM motor. The start circuit has to cut out
    at something like 25% of operating speed. But I'd expect a ceiling fan
    to be rather easy to hand start.

    I burned out the start cap. in my pressure washer. I could still start
    it by giving the entire unit a sharp twist about half the time.
  7. Quickly. Before the three day warrantee expires.
  8. t.hoehler

    t.hoehler Guest

    These motors are not synchronous, just permanent split capacitor
    motors. And yes, the phase shifting caps open, rendering the motor a hummer
    only. Usually cheap ass Chinese capacitors - price point items. No amount of
    spinning will get this puppy going. Only cure is a trip to the store for an
    exchange. I see why you want to fix it though - it's a bear to take the damn
    thing down and rebox it!
  9. jasen

    jasen Guest

    bullshit. (most unlikely to be synchronous)
    sounds like it.
    the capacitor should be fairly cheap to replace, but get one that meats the
    relevant safety rules.

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