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Help with basic elec. motor stuff

Discussion in 'Electronic Repair' started by Puddin' Man, Apr 9, 2012.

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  1. Puddin' Man

    Puddin' Man Guest

    So my little 2-speed fan just stops running.

    I workbench it and try to figure what the problem might be. It's
    getting power. Nothing appears to be burnt.

    Can anyone identify the type of elec. motor in the pics?

    The pics are the 2 sides of the same motor.

    Any info and or hints about the principles of operation of this type
    motor would be much appreciated.


    "Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule."
  2. gregz

    gregz Guest

    Shaded pole rings a bell. I have had motors like this that lock up on power
    up. It would be hard to turn. It should turn freely with no power. If
    nothing happens I would suspect open winding.

  3. Winston

    Winston Guest

    Search on "shaded pole motor".

    More info please?
    How long does it run before it stops?
    About what speed does it run? About 3400 RPM?
    Does it stop abruptly or does it slow down and then stop?
    Does it stop when you move the various wiring bits?

  4. Puddin' Man

    Puddin' Man Guest

    Thanks for ID. Interesting, but over my head. :-(
    Purchased ~ 4 years ago.
    Used extensively mostly in summer of 2011 (maybe 10 hours/day).
    Made strange sympathetic vibration sound, ~C#.
    Worked OK about 3 weeks ago.
    Stopped functioning altogether.

    The shaft turns freely. No evidence of a heat problem.
    Gets 120v thru feed wires.
    No contacts on coil (cannot test voltage there).
    Just sits there and looks dumb when powered.

    Can't find -any- specs on it (Model MH-20UL)

    Chinee wonder mystery, probably not worth further consideration?


    "Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule."
  5. Jamie

    Jamie Guest

    You have a shaded pole motor..

    check the spindle slop or stiffness.

    You don't want either.

    also, did you recently spray this down with parts clearer of
    something? Does the core seem to get hot to you?

    If yes to either, trash it.

  6. Winston

    Winston Guest

    'Sounds like a failed bearing.

    As Michael mentioned, presenting 120 V to the coil does
    not necessarily mean there is current through the coil.


    'Probably true. Please use your multimeter to measure the resistance
    of the switch when on, wires, connectors etc.

    As Michael implies, your first - order test would be a resistance
    measurement from prong to prong on the unplugged A.C. connector.

    If it is 'open' and the switch and power cable tested OK, you're
    probably not going to be able to repair the motor economically.
    It is your call whether you want to unwrap the winding to discover
    an open fuse as a matter of edification and entertainment,
    before you throw it away.

    If you are really economical (as I can be), you can salvage a low-
    mileage shaded-pole motor out of a scrapped microwave oven and
    use that in your fan. I see four in my scrap box from where
    I'm sitting! :)

    Shaft adapters are left as an exercise.

    --Winston<-- Salvage Safely! Some components can maintain sufficient
    charge to knock you on your keester.
  7. Puddin' Man

    Puddin' Man Guest

    I doubt it. It made that sound all summer. No evidence of a burnt
    bearing. No play in the fan shaft.
    Such is the case.
    All of that is well beyond me.

    I don't even know how to properly test because I
    don't understand the wiring. :-(

    Spare a minute? I comprehend that I can wrap wires around a conductor, apply
    current, and have an electromagnet. If I can time the switching of polarity,
    and place the em in the field of a fixed magnet, I'll have basic components
    of an elec. motor. No?

    Alternatively, I could have + and - fields formed with the em, and have a
    fixed magnet as an armature (??) thus constituting a "motor".

    But I'm still miles from understanding how this shaded pole motor works.
    It looks like it has a big fixed magnet (but with copper tubes running
    around it), a large winding presumably between the N and S poles, and
    a separate armature (with fan shaft) in the middle of the fixed magnet.
    This describes what I see in the pics.

    If you can explain how these components relate to my miniscule understanding
    of the basic components of a "motor" (above), I would award you with a
    (virtual) "Cigar And A Beer". :) I'm obviously missing a bunch. Hope I
    haven't mangled the terminology too badly.


    "Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule."
  8. Winston

    Winston Guest

    Series circuit. AC hot to switch, from switch to motor,
    from motor to AC neutral, pretty much.
    That is what you see, yes?
    See below. :)
    Please review the results of your Internet
    searches WRT motors in general and shaded pole motors
    in particular. I expect some have very illuminating
    illustrations and perhaps a cartoon or two.

    My understanding of these things is marginal
    at best, so I hereby bump your question to
    those more knowledgeable and articulate.


  9. Puddin' Man

    Puddin' Man Guest

    No. All I'm really familiar with is common house wiring. 3
    wires, black (and maybe red), white, and bare (or green).
    Connect black and white to device, close circuit, device
    runs (if functional). 120v potential between black and
    white. 240v between black and red (?).

    Per the pics, shaded pole is wired red, black, and
    blue. Where is Common?


    "Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule."
  10. Puddin' Man

    Puddin' Man Guest

    I ran a search on "tapped coil": wasn't much help. Howzit woik?
    Unplugged. Black to red: 0. Black to blue: 0. Blue to red: 1.

    Found more info:

    Thermo-fuse Rot CW
    |--------- Black --------------------------
    | |
    |--------- Blue (Lo) ---------- Line
    | |
    |----------Red (Hi) -----------------------
    Not observed.
    It just stopped running. Shaft turned freely.

    I'm not really concerned about this motor. I just *hoped* to understand
    something of it's electromagnetic workings and how that related to the
    wire colors, etc.


    "Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule."
  11. Puddin' Man

    Puddin' Man Guest

    Thank you.
    Thank you, again.
    This is the sort of explanation I sought.

    Many thanks,

    "Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule."
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