OT? Delta Repulsion induction motor won't start on its own
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  1. #1
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    Default OT? Delta Repulsion induction motor won't start on its own

    It's on a Delta drill press, started on its own last week, but doesn't now, just sits and hums. If I give the drive belt a fast enough yank, it'll come up to run speed and operate normally.

    It came from my Dad's estate, no idea how long it's been since it were apart, possibly not since being built. It has a mechanical switch in the junction box linked to the front of the dp with a long rod so I don't really want to replace it with something else. Doable, and prob quieter, but don't want to rig up another switch arrangement.

    Were this a cap start induction motor, I'd know exactly what to do, but this is a different animal.

    Any good ideas on what's wrong with it? (And how to fix it?)

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    neilho, with this type of motor you can change its rotation by changing the position (angle) of the repulsion ring. It is possible that yours has gotten shifted into an intermediate position where it doesn't start because it is trying to start it both directions at once.

    On my Rockwell wood shaper, the R-I motor has a lever to move the ring to get CW and CCW rotation; on my lathe, I have an R-I motor that did not come with such a lever, but I was able to rig one up - there was a "window" that accommodated a lever. On a drill press ... maybe they did not include a provision for adjusting the ring, so you may have to open it up.

    On edit: for clarity, on both of my R-I motors, it takes a relatively small angular movement to change from CW to CCW or vice versa - maybe 10-15°. So it doesn't have to be very far out of position to start humming instead of turning.

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    Hmmm.

    It will run readily in the wrong direction if I yank the belt that way, which points towards your possibility. Guess I'll have to open it up.

    Puzzled as to what could have happened to shift the repulsion ring. Maybe stuck because it has to move during operation and hasn't been lubed/cleaned in years ? I'm speculating...

    Thanks.

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    RI motors operated by having the brush ring contact the commutator and then lifting when the motor is at speed. So, it sounds like the brushes are not making contact as in mechanical hangup or stuck in the holders. The brushes lift when the motor is at speed. A good cleaning would probably take care of the problem.

    Tom

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    That's interesting - I've never observed the lifting of the brushes, but then again, I haven't specifically looked for it. I'll have to take a closer peek at one of my R-I motors as I start it up!

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    Repulsion-start induction-run
    These were used where high starting torque was required. They started as repulsion motors, but once they were running at a sizable fraction of full speed, the brushes were lifted mechanically and all commutator bars were short-circuited together to create the equivalent of a squirrel-cage induction motor.

    Repulsion motor - Wikipedia

    Tom

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    Thanks, Tom. Now all I need's a rainy day to take it apart and clean it....

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    Try sprayering the inside of motor with map/maf sensor cleaner. An automotive spray. But make sure it's unplugged and wait a couple of hours before trying. Mine did the same thing after I took it apart. Like the other members said try loosening the two screws a bit on top off the motor, open the plate that allows you to look inside of motor. I think I used a dowel to gently rotate the ring a bit on the inside. I read this fix by googling r-I motor not running. Somebody from India has video also on YouTube about these motors . Good luck


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