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shaded pole sync report



Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <FutureT-at-aol-dot-com>

All,

I modified a 3200 rpm shaded pole induction motor
for 3600 rpm sync operation.  The procedure worked, but
the motor locks at 93 volts with no load, it was barely able 
to lock with a 3.25" rotor.  It's rated at 2.4 amps.  Shaded
pole motors are cheap and simple.  A 3200 rpm shaded pole
motor has only two windings.  It has no run or start cap, and
no centrifugal start switch, nor any external relay start switch.

The mod was interesting because there is an 1/8" gap between
pole pieces, and there was a depressed area next to the gap,
about 7/16" wide.  The armature is 1.5" in diameter.  I first made
the two armature flats 3/8" wide, but the motor did not sync-lock.
Next I widened them to 1/2" wide, but it was still NG.  Even 140 
volts input did not lock the motor.  Finally I figured the flat must need
to be equal to the total width of the depressed area plus the gap.  
This is equal to 9/16" total, so I made the flats that wide and the
motor locked as described. 

For small motors of a given physical size and current rating, 
a cap run motor is a lot stronger and better for sync modification,
than a shaded pole motor.

Cheers,
John