Cancellation of torque ripple accompanying space harmonics in SPMSM

In permanent magnet machines, the primary cause of pulsation torque, which is the sum of the cogging torque and the pulsating components of magnet torque, is space harmonics contained in the magnetomotive force due to the armature current and in the air gap flux density due to the rotor permanent magnets. The pulsation torque causes vibration and acoustic noise and reduces the performance of the machine in terms of speed and position control. We herein propose a method for canceling the magnet torque pulsation and cogging torque. The present paper describes the torque equation of surface-mounted permanent magnet synchronous machines, the method for canceling the pulsation torque, and the results of a computer simulation, which demonstrate the validity of the proposed method.