Analysis and Suppression of Electromagnetic Ripple Torque of Surface-Mounted Permanent Magnet Synchronous Motor with Similar Number of Poles and Slots

In order to improve the positioning accuracy and stability of the servo system, the torque ripple of permanent magnet synchronous motor (PMSM) is analyzed. As the cogging torque and the reluctance torque of surface-mounted PMSM with similar number of poles and slots are small, the electromagnetic (EM) ripple torque caused by the interaction effect between back electromagnetic force (EMF) harmonics and armature current harmonics is the main component of the torque fluctuation. Firstly, the generation cause and the characteristics of EM ripple torque are analyzed and the 6th, 12th, 18th harmonics are the main components of the EM ripple torque. Then the rotor step skewing method and harmonic current compensation method are investigated and analyzed to reduce the EM ripple torque. Finally, the effectiveness of the two optimization methods are validated by finite element method (FEM) and prototype experiments.