Permanent Magnet Design for Torque Ripple Reduction in PM-Assisted Synchronous Reluctance Motors

To ensure the smooth and reliable operation of high performance drives it is essential to diminish the parasitic effects such as pulsating torques produced by the traction motor. Inherent large torque ripple is accordingly the well-known challenge of Synchronous Reluctance Motors (SyRMs) for such a high-performance application. This paper aims to investigate the opportunity of SyRM torque profile smoothening via inserting the Permanent Magnet (PM) materials into the rotor structure. For this purpose, the Conventional PM assisted SyRM (CPMaSyRM) rotor and a recently introduced axially segmented rotor configuration, i.e. the axial integration of a PM rotor and a SyRM rotor, will be studied. It will be shown that although the torque ripple alleviation in the CPMaSyRM design via PMs parameters optimization is too restricted, the axially segmented design is significantly capable of pulsating torque compensation. The PM material utilization, power factor, and efficiency will also be evaluated for two motors. Furthermore, a computationally efficient algorithm will be proposed for the axially segmented rotor torque profile optimization, and the effect of axial field coupling will be discussed.