Design and performance analysis of inner-rotor IPM PMSMs for cogging torque and ripple reduction in EV applications

The permanent magnet synchronous machine (PMSM) is a rare earth magnet-based motor, characterized by elevated power density, high torque density, and additional reluctance torque in the total torque operating points. This paper presents the design and validation of a 48 V, 20 Nm inner-rotor interior permanent magnet (IRIPM) PMSM aimed at minimizing cogging torque and torque ripple through the selection of an optimal slot-pole combination, an innovative winding configuration, and optimized magnet geometries.Three magnet configurations—V-shaped, bread-loaf, and straight (horizontal) are investigated to reduce cogging torque to less than 10% of rated torque and torque ripple below 5%. Interior permanent magnet PMSMs are particularly suitable for mid-range EV applications due to their ability to deliver high torque at medium operating speeds ranging from 1000 to 10 000 rpm. However, conventional slot-pole combinations often exhibit elevated cogging torque and torque ripple. To address this challenge, rotor saliency is optimized through geometric modifications. Finite element analysis (FEA) is carried out using Altair Flux™ 2D in this work to compare the electromagnetic performance of a PMSM motor with three different geometries. Neodymium-Iron-Boron (NdFeB) composite permanent magnets and M230-35A silicon steel laminations are employed. The effects of air-gap variation and temperature on cogging torque and torque ripple are also evaluated. The results demonstrate that the proposed horizontal magnet configuration achieves superior electromagnetic performance with minimal torque ripple, making it suitable for two-wheeler EV applications.