# controlling the speed of a shaded pole motor

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#### Atlas

I am doing a project on controlling the speed of a single phase shaded pole -permanent magnet- ac motor. I want to know how speed is related to the voltage applied to the motor. I dont have any algorithms and idea for this. Can anyone please help? Any site? PCB? Sample of circuit. Step by step please.

If i wont do this project, i failed this season.

Warm regards,

M

#### M Griffin

So far as I know, that is a synchronous motor and the speed depends on the frequency, not on the voltage. If you look in a standard motor textbook on how shaded pole motors work, you will see why.

You would need a circuit that outputs a variable AC frequency. That would probably involve a circuit that rectifies the AC to DC, and then produces an AC power output at a different (variable) frequency.

C

#### curt wuollet

You can actually achieve a degree of speed control with wound field shaded pole motors with voltage. It's very soft, (poor speed regulation) and useful mostly for fans and small blowers. I don't recall ever seeing an AC PM shaded pole motor.

In the wound motors the field poles have the shading ring. I would suppose the rotor would be PM unless they've got slip rings. And I would expect it to behave in much the same way except voltage dependence would be less as the rotor flux is constant. I would intuitively guess that you would have a knee where above a point you are in sync with the line and below that point you have some control.

My corn stove is full of voltage controlled shaded pole motors, I think they are cycle counting, but they work so I haven't thrown a scope on to see what they are doing. Might be phase controlled, but that would be a lot for a PIC.

Regards
cww

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