Optimization of the Magnetic Pole Shape of a Permanent-Magnet Synchronous Motor

A kind of six-slot/four-pole permanent-magnet (PM) synchronous motor is very popular nowadays for the advantages of saving coppers and because it is easy to manufacture. The magnetomotive force (MMF) produced by the six-slot stator windings are not symmetrical under the four poles, and more harmonics exist in the air gap, which will increase the torque ripple and noise. In this paper the rotor structure is optimized from the aspects of magnetic-pole embrace, magnetic bridge, and magnetic-pole eccentricity to obtain better air-gap magnetic field distribution and torque curves