"Wild Bill" wrote in message
...
You've shown a lot of curiosity in the past, so this would be a good
opportunity to examine this motor closely to determine what type it is.
My practice is to open any used electrical devices.

;-) Tried last night but the nuts are too tight on the screws...

I'm certain that there is no internal capacitor, and no centrifugal
switch.

Unforunately, I removed the injection-molded glass-filled-plastic cover that
contains one 6uF 370VAC oil filled style capacitor.

You should double-check the winding resistance.. they usually read like
center-tapped transformer winding (20, 20, 40 ohms for example).

Did. Only one winding shows up, everything else climbs to infinity on
account of being capacitive. I've listed the values measured. Likely
inductance is partially canceling the capacitance.

These are
sometimes described in motor books as 2 phase motors (derived from the
capacitor terminal that's not connected to the AC source/line), but
otherwise known as PSC, permanent split capacitor as Ned mentioned.

If this were true, it would start and run in the respective direction
depending on what leads I applied power to. It doesn't. It doesn't move at
all with power on just the start winding, FWIW.

The electricmotorwarehouse spec sheets state that it's a PSC ball bearing
motor with CCW rotation. The image shows a large oval-shaped capacitor
attached to the motor in the picture, indicating that it's a run
capacitor (maybe it was removed from your motor). The list notes
indicate that it would be a 4uF 370VAC cap for the ball bearing motor.

6uF is mentioned on the sheet for D827, actually. It looks exactly as
pictured and appears to be whole.

That means no start/run windings, because it's not a split phase
capacitor start motor.

Which unfortunately isn't born out by the fact that one winding needs power
to get it to start turning.

Motors in the speed range of this one are typically designed/rated for
fan duty, but that doesn't neccessarily mean that it can't be used for
other purposes.

Guy I got it from said it came from a school ventilation system, not
suprising.

You'll most likely never see a 700 rpm motor that's a split phase
motor with start/run windings.. they're generally always 1725 or
3450 rpm.

So what is this? It doesn't measure nor respond as a PSC does.

The plug you described may have been specific to the appliance that the
motor was intended for, and the capacitor may have been mounted somewhere
off the motor.
A capacitor value of 2 to 10uF would probably work as long as it's an
AC cap rated at 370VAC. A cap with a diferent value than specified may
affect the operating temperature and produce a small change in speed.

Ok, too bad I only have 20 and 30uF caps!

Tim

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