Torque Ripple Analysis of Line-Start Permanent Magnet Synchronous Motors

On account of the introduction of the rotor cage, the inherent torque ripple is a challenging problem in the design of line-start permanent magnet motors (LSPMSMs). In order to reveal the influence of the rotor cage on the torque ripple, we studied the torque ripple of the LSPMSM using a torque separation method based on Maxwell's stress tensor. A 280 kW, four-pole LSPMSM is used as the research object. The contribution of rotor slotting and bar currents to the torque ripple is evaluated. The relationship between the torque ripple and the harmonic magnetic field induced by rotor slotting and bar currents is obtained. Furthermore, the effect of rotor slotting and bar currents on the torque ripple of LSPMSMs is determined.