A METHOD TO REDUCE TORQUE RIPPLE OF PERMANENT MAGNET SYNCHRONOUS MOTOR

A method named as Magnet Shifting to reduce torque ripple of permanent magnet synchronous motor is disclosed. A way of reasonably choosing the repeating unit of magnetic pole, the shifting ways and the shifting angle calculation of the first and second magnet shifting is described, which are carried on the repeating unit of magnetic poles individually or repeatedly to improve the performance of the motor. The method can be applied to surface, surface-inset and inner-embedded permanent magnet motors, which can reduce torque ripple caused by different torque components, including cogging torque, reluctance torque or permanent magnet torque. It also can quickly calculate the shifting angle of the magnetic pole by choosing repeating unit reasonably. Magnet shifting can effectively enhance the sinusoidal degree of back electrodynamic force (back-EMF) waveform, where the repeating units can offset the torque ripple between the maximum and the minimum value to reduce the different torque harmonics. Also, the output torque can be maintained nearly to the original value while less vibration noise of the motor is inevitably introduced.