Optimal Torque Ripple Reduction Technique for Outer Rotor Permanent Magnet Synchronous Reluctance Motors

Bonthu, S., Tarek, M., & Choi, S. (2018). Optimal Torque Ripple Reduction Technique for Outer Rotor Permanent Magnet Synchronous Reluctance Motors. IEEE Transaction on Energy Conversion. 33(3), 1184-1192.

Torque ripple reduction has been one of the main considerations in the optimal design of traction motors, such as permanent magnet assisted synchronous reluctance motors. Several design techniques including optimal slot/pole combination, stator slot and rotor magnet skewing, and shape optimization of rotor flux barriers have been studied intensively to reduce the torque pulsations in the internal rotor reluctance motors. However, internal rotor reluctance motors involve power train complexity and space constraints in the traction application. On the other hand, outer rotor motors can be designed optimally to eliminate these drawbacks and in addition, produce higher power density. In such outer rotor reluctance motor designs, torque ripple plays crucial role as the in-wheel motor is under duress of consistent rotational forces. Furthermore, optimization of outer rotor in-wheel motors needs to be thoroughly investigated to reduce the torque ripple and to generate higher torque density. In this paper, a rotor shape optimization based on design of notches and rotor flux barrier is presented. Detailed optimization process in adjunct to analytical and simulation results comparison is presented. Finally, optimal designs are fabricated and tests are conducted on the 3.7-kW prototypes to validate the proposed design-optimization theory.