On 8 Mar 2007 13:37:06 -0800, "
put finger to keyboard and composed:

I disassembled the motor cleaned it and lubricated it with ATF. It
appears to be in very good condition. There is no end play in the
bushings and very little apparent wear. It starts better now and comes
right up to full speed, however the speed is 1720RPM either loaded or
running free. Same as before the cleaning. There seems to be four
poles which would suggest 1800RPM as you mentioned. Is it
theoretically possible for a four pole motor to operate at 1720RPM?
Varying the line voltage around 120V has very little effect on speed
so it appears that it is running synchronously. There is no capacitor
externally or internally. I just can't imagine what could have
possibly failed (if something did), to cause this. Lenny

Induction motors need "slip" to operate properly. A figure of 5% or
less is typical.

http://www.electricmotors.machinedes...bdeee11_7.aspx

"Synchronous speed is the absolute upper limit of motor speed. At
synchronous speed, there is no difference between rotor speed and
rotating field speed, so no voltage is induced in the rotor bars,
hence no torque is developed. Therefore, when running, the rotor must
rotate slower than the magnetic field. The rotor speed is just slow
enough to cause the proper amount of rotor current to flow, so that
the resulting torque is sufficient to overcome windage and friction
losses, and drive the load. This speed difference between the rotor
and magnetic field, called slip, is normally referred to as a
percentage of synchronous speed."

- Franc Zabkar
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