Cogging torque and torque ripple reduction of surface-mounted permanent-magnet synchronous motor considering rotor stress

Abstract

Permanent magnet synchronous motor is widely used in a high-performance control system, but its cogging torque and torque ripple will affect the precision of the control system. Stable motor operation necessitates the reduction of slot torque and torque ripple. The stress of part of the rotor will also change after reducing the reduce the slot torque and torque ripple. This paper reduces the slot torque and torque ripple considering the change of rotor surface stress, which has reference value for the design of magnetic pole moving rotor. Firstly, experiments verify the accuracy of the finite element model. Secondly, the slot torque and torque ripple under different polar arc coefficients are analyzed in ANSYS Workbench, and the appropriate polar arc coefficients are obtained. In addition, to further reduce the torque ripple, three pole changing methods are proposed, and the slot torque and instantaneous torque of each pole changing method under different shift angles are analyzed. The simulation results show that the torque pulsation can be significantly reduced by the two adjacent pole-changing methods, and the average torque changes little. To analyze the stability of the rotor after pole changing, the stress analysis of the magnetic pole moving model is carried out. The simulation results show that the filling block can effectively reduce the stress concentration of the sleeve, so it is necessary to assemble the filling block in the magnetic pole moving rotor. According to the results of torque and stress analysis, it is showed that the rotor model is optimized by the method of the adjacent-pole shifting Angle of 5 degrees, and the slot torque is reduced by 74.92%. Finally, to ensure the safe operation of the rotor, the rotor dynamics analysis is carried out to study the radial displacement of the sleeve under the rated speed. According to the simulation results, the magnetic pole movement has little effect on the critical speed, and it increases the radial displacement response of the rotor. This paper reduces the slot torque and torque ripple considering the change of rotor surface stress, which has reference value for the design of magnetic pole moving rotor.