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Thread: Ceiling fan speed problem
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Old 09-14-2022, 02:22 PM
drstevens drstevens is offline
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Default Fan Speed
FYI: The only variables that control speed of a single-phase AC motor are the frequency and the number of poles in the motor. The frequency is fixed at 60 cycles from the power company. Your pull chain switches in and out the correct number of poles for the speed.

The formula is: S= 120F/N, where N is the number of poles and F is the frequency.
As an example: At 200 RPM the fan has 36 poles. So, you can see why ceiling fans are so large and heavy.

The capacitor has nothing to do with speed. It increases starting and/or running torque while reducing starting current. Pretty amazing, huh!

If the fan will start by hand-spinning the blades, then you have a bad capacitor. If not, then it is the switch (or really bad bearings!) Poles and windings hardly ever go bad.
Good luck! (P.S. I taught motors & controls at Ohio University for 37 years)