Power Factor Vs. Motor Poles
Power Factor Vs. Motor Poles
(OP)
Working on a project requiring very high motor efficiency. In reviewing motor selections, I notice with changes in the number of poles in asynchronous motors, PF changes. Can anyone explain why?





RE: Power Factor Vs. Motor Poles
Magnetizing a longer circumference to the same flux density will require more magnetizing amperes.
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RE: Power Factor Vs. Motor Poles
RE: Power Factor Vs. Motor Poles
The rotor diameter will increase with the factor depending on p^ (2/3) that means for p=2 [4 poles] will be 2^ (2/3) =
1.587 times the diameter of 2 poles motor [roughly]. But the magnetic flux density will increase 2 time [as the air gap length per poles will be 1/2].So, ultimately, the flux density will increase 2/1.578= 1.267 times [roughly, of course!].
That means the saturation of the magnetic core [mainly in the teeth region]will be more pronounced in return, so the magnetizing amperes will increase[ as electricpete said].But in the same time also the notch leakage reactance will increase[ as edison123 said].The influence of the magnetizing current on the pf is evidently more important than the leakage reactance.
Best Regards
RE: Power Factor Vs. Motor Poles
RE: Power Factor Vs. Motor Poles