Wavelet Analysis of Permanent Magnet Synchronous Machine Flux Density Harmonic Content With Different Pole Number Designs

This paper utilizes the wavelet packet transform to study the effects of decreasing the number of slots per pole per phase on the harmonic behavior of the working flux density in the air gap. A surface mounted PM motor is used as an example. The original design contains 6 PM poles and 36 stator slots with three phase winding embedded. The rotor is redesigned to have 4, 8, and 12 poles mounted on the same rotor iron surface and the winding is rearranged to form 4, 8, and 12 stator poles respectively with the original 36 slots stator. The air gap flux density waveform along a round path close to teeth surface is obtained from the FE solutions. The harmonic behavior of air gap flux is studied with a wavelet packet transform. It is found that an increase the number of poles causes an increase in the harmonic content of the air-gap flux density and the accompanying effects on the proper operation other components connected to external circuits.