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1600 RPM sync. modifictions
All
With all the talk about 1600 R.P.M. sync. gaps & how many flats to
grind on the armature, I decided to experiment with one today at work.
Some time back, I took a small shaded pole motor, like are found in small
cooling fans in microwave, fridges, bathroom vents, etc, and ground 2
flats on the armature. This was a 3000 R.P.M. rated motor, but they
actually run closer to 3550 R.P.M. unloaded, and this one was around 1/60
H.P. The results were poor, no sync. operation even with a totaly
unloadedshaft. I attributed this to the weak phase shift created by the
shading coil.
Then today, I took a 1550 R.P.M. 1/30 H.P. Dayton brand shaded pole to
work for modifications. This was a 3.3" dia. size. There are 4 poles 90
deg. apart and each of those poles had a small area driven out of phase
realitive to the larger area by way of a shaded turn, or a shorted turn,
thus a shaded pole design. I thought maybe this motor might be a little
more suitable for sync. conversion even though it was a shaded pole
design. Incidently I bring up shaded pole motors since they are
realitivly cheap.
I have heard grinding 2 flats on a 1550 R.P.M. armature works, so I
ground 2 flats, assembled & tested. Low and behold, the little shaded
pole motor ran sync. and self started easily. I loaded the motor with a
6" x 1/4" fibreglass disk & found it locked in sync. at 110 volts,
marginal for 120 volt operation. Then tried a 6" x 1/8" disk. This was
much better, locking in around 80 volts. Note that there were no
electrodes on the disks. This would further add air resistance & load
the motor more.
With my experience in sync. conversions to split phase, perminent split
capacitor, and capacitor start motors, the addition of the shaded pole
motor makes about all a/c induction motors good canidates for sync.
modifications. With as little as a high speed die grinder with a
carbide disk, and a good flat file along with a bench vise, sycn.
conversions are realitivly easy & fast to perform. A mill machine is
nice though if handy.
Comments welcome
Kevin E.
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