Auxiliary Notching Rotor Design to Minimize Torque Ripple for Interior Permanent Magnet Machines

This article proposes an auxiliary notch design method for the interior permanent magnet (IPM) machines for suppressing torque ripple. The key principle of this design method is to identify the main source of torque ripple, then guides the modification of reluctance variation along the rotor surface. First, the theoretical analysis of the torque ripple in IPM machines are investigated to guide the auxiliary notches design. Based on this, a spoke-type IPM machine with permanent magnet torque as the main component and a U-type IPM machine dominated by reluctance torque are analyzed, respectively. Additionally, the relationship between the shifted angle of the auxiliary notch and the order of torque ripple is revealed. Furthermore, the electromagnetic performances are investigated by the finite-element method. After using auxiliary notch design, the torque ripple is significantly reduced and the torque amplitude is almost not sacrificed. Finally, a spoke-type IPM machine prototype is manufactured for experiments to evaluate the effectiveness of the theoretical analysis.