question about starter cap and oiling a synchronous motor

Discussion in 'General Electronics Chat' started by tpny, Apr 18, 2013.

  1. tpny

    Thread Starter Member

    May 6, 2012
    216
    0
    I think it's a synchronous motor, it plugs straight to 110VAC and drives a fan blade.. Motor hums but doesn't turn when powered.

    It has a cap rated 2uF, I replaced it still doesn't move. I replaced it again with a 4uF and can get it to move when I spin start it with my fingers. Q: Is it ok to double the cap to 4uF like that?

    Also, can I oil the gap in between the rotor and the stator? I did that and seems fine as it's spinning now. But should that gap not be oiled?
     
  2. #12

    Expert

    Nov 30, 2010
    16,298
    6,809
    That gap should be a gap. It never needs oil because nothing touches. Apparently, it does touch. Fix the gap.

    And put the capacitor back to the size it's supposed to be.

    Trying to fix a mechanical problem with electrical experiments will only result in a quick failure.
     
  3. tpny

    Thread Starter Member

    May 6, 2012
    216
    0
    OK noted! But what might be somethings to watch out for in this case with the motor where I doubled the cap from 2uF to 4uF? Thanks!
     
  4. #12

    Expert

    Nov 30, 2010
    16,298
    6,809
    Inappropriate current amount.
     
  5. tinkerman

    Member

    Jul 22, 2012
    136
    34
    Post a picture if you can. If this is the style I'm thinking. The rotors should never touch on any motor. Did you check the bearings? Many use a bronze bushing. They dry out and wear, then the rotor rubs and won't start. If oiling made a difference then it's likely worn out. Check the laminations. There should signs of rubbing if I'm right. It's possible to replace the bushings if you can find a new one or salvage a good used one. Usually it's better to replace the motor.
     
  6. Metalmann

    Active Member

    Dec 8, 2012
    700
    223
    Press in new bearings, or Oilite bushings.
     
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