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how to "repair" a motor magnet?

Discussion in 'Electronic Repair' started by Herbert Widlok, Sep 4, 2003.

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  1. Hi
    Is it possible to remagnetize permanent magnets on stepper motor
    rotor, that was partially demagnetized, when I have pulled it out of
    stator? I knew that this could happen, but I never believed that this
    will happen to me. And how they are mounting such motors in industry?

    Thanks,
    Michael
     
  2. Sad to say but you may need to replace the complete motor as an assembly.
    Unless you can get the manufacturere to send you a replacment magnet set.
     
  3. In theory, it is possible. But as a practical matter, probably not.

    They have to use a "keeper" when removing the rotor to maintain the
    field.

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  4. You could try replacing the magnet with a neodymium/rare earth magnet.
    Those are much stronger than the ferrite stuff used in most motors, so a
    much smaller magnet than the original one would do. Check out
    http://www.wondermagnets.com/cgi-bi...ets_and_Magnetism;Permanent_Magnets;Neodymium

    Neodymium magnets can also be found in hard drives, crack one open if
    you have an older one lying around and take out the magnets to get a
    feel for those beasts.

    HTH,

    Andi
     
  5. FreeSkier

    FreeSkier Guest

    It's not that easy. A magnet is not just a magnet. Typically, the
    magnetic material is installed on the rotor and placed in a magnetizing
    fixture. The magnetizing coils are energized and this places the
    desired pattern on the magnets. You can't necessarily tell what the
    magnetizing pattern is by looking at the magnets (N-S are not always at
    the ends). To further complicate things, the rotor was probably skewed,
    meaning the magnetic "charge" on the rotor was not parallel.

    In your case, you will definitely have to install magnetized magnets -
    unless you build a magnetizing fixture. Either reverse engineer what's
    remnant on the rotor or get a new motor.
     
  6. Thanks You all for replays. It seems that I will have to get new motor or
    use old one that now have 50% of normal torque. I hope that this will
    suffice for me.

    Michael Widlok
     
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