Reduction of Torque Ripple in Inset Permanent Magnet Synchronous Motor by Magnets Shifting

This paper proposes a method of reducing total torque ripple by magnets shifting. The key of this method is to consider the reluctance torque ripple, because the reluctance torque ripple is the main source of torque ripple in inset permanent magnet synchronous motor. This method is realized by appropriately choosing Repeating Unit, which indicates a group of poles producing torques with consistency in waveforms and phases. Meanwhile, the uniform analytical expressions of torques with magnets shifting are established, including cogging torque, reluctance torque, and total torque. Moreover, the total torque ripple can be reduced greatly, and the average total torque loss is acceptable when one pole-pair is chosen as one Repeating Unit and the shifting angles of Repeating Unit are 3.75 and 1.875 mechanical degrees. These theoretical analyses are verified by the finite-element method.