Does anyone know what type of rheostat will slow a PSC motor with a run capacitor. It is a gear motor that final turn is 86rpm, but I don't know what the initial speed is. It is 110 volt and 2.1 amp. 60Hz When I hooked up a speed control I purchased on eBay, (and their ad stated that it would control a PSC motor) when I hooked it up the only thing it varied was the sound of the motor. No change in speed.

Any insight would be appreciated.

Will

See if your speed control has a trim pot. However I don't recommend using a solid state control on a gear reduction motor, it will probably stall out. You can try wiring a capacitor in series with the motor, or even a capacitor stepped control (like a 3 speed ceiling fan control from Lowes) but that too might stall out, or chew the gears.

Gear motors are really designed to go at the speed they're designed to go.

It did have a trimpot and only varied the sound again. This is a very burly motor, I doubt I could stall it, but what I am trying to turn has very little resistance. What is the difference between what I purchased and a Lowe's fan speed control? I would also like to hear more about the cap wired in series. Your input has helped the most, and I really appreciate it.

Will

Solid state control is infinitely variable. Capacitor control has 3 or 4 distinct speeds i.e. high medium and low.

If you don't know, don't bother replying

Three Ways to Control a Single-Phase Induction Motor - 2004-12-13 00:00:00 - Design News

This article http://powerelectronics.com/mag/506PET23.pdf sums it up fairly well:

Low torque applications: Phase control works

High torque applications (Yours): Need to move to VFD or Variable Frequency Drive

It's a single phase motor, pay attention. Those articles are quite amusing.

Sorry, you are correct.

Quote:

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Originally Posted by carrara68

If you dont know, don't bother replying

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What are you talking about? I answered your question.

There are basically two ways to change the speed of an AC motor. Alter the frequency or alter the number of poles. Here is the standard formula for AC motor speed.

N=120f/P

N=speed in RPM
f=frequency
P=number of poles

120 is a constant and does not equal voltage, in fact, voltage does not enter into the equation. In other words, a rheostat will not alter the speed of an AC motor.