Can we design odd number of poles (3,5,7...) in a three phase induction motor?

11 November 2013 1 10K Report

I know poles are in even numbered, but can we?

The Russians did some work in this in the 1940's. Remember that at the time material was scarce so they were trying to be creative under very limiting conditions. The idea was to be able to achieve odd pole speeds with even number of poles. The idea was to have short circuit windings in the stator in order to extinguish the rotor field as it passes through the shorted stator windings. This gave us the odd pole speeds. It didn't work very well, we tried it, had wound a stator to do exactly that but the time constant was too fast so the rotor field never extinguished completely.

If you are curious, check out E. R. Laithwaite's work on Arch or Arc motors.

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