The Modified Model of Third-Harmonic Shaping for a Surface-Mounted Permanent-Magnet Synchronous Motor Under Parallel Magnetization

This article establishes an optimized third-harmonic shaping model in order to reach the goals of high power density and low torque ripple of the surface-mounted permanent magnet motor. The establishment of the model takes the nonideal factors into consideration, including PM relative permeability, stator slotting, pole leakage, pole edge effect, and magnetic circuit saturation. The formula of third-harmonic shaping and the optimal third-harmonic injection factor a
_m(m)
are derived from the model. Then, a finite-element model was established to compare the electromagnetic performance of different magnetic poles. It is found that the average torque of the modified third-harmonic motor is 3.5% higher than that of the simplified third-harmonic motor, and the torque ripple is 47% lower than that of the simplified third-harmonic motor. This proves the superiority of the modified model. And experiments demonstrate that the modified model is feasible and effective.