Design of Optimal Winding Configurations for Symmetrical Multiphase Concentrated-Wound Surface-Mount PMSMs to Achieve Maximum Torque Density Under Current Harmonic Injection

Torque density of multiphase PMSMs can be enhanced by using current harmonic injection (CHI) techniques that utilize potential torque-producing nonfundamental spatial harmonics of the stator winding function (SWF) to produce an additional average torque. This possibility is ignored in the existing multiphase winding design methods that only aim at maximizing the fundamental spatial SWF harmonic, thus neglecting the remaining torque-producing spatial harmonics. These methods are also restricted by the number of machine phases. Motivated by these drawbacks in the existing methods, this paper proposes a novel heuristic algorithm for designing symmetrical multiphase concentrated windings with maximized average torque by considering all the nonfundamental torque-producing spatial SWF harmonics. The proposed approach is valid for any number of phases. Accordingly, an index is proposed to evaluate the multiphase winding performance in terms of its torque density under the CHI technique. The proposed method is formulated by using analytical treatment of the SWF, based on which, a systematic approach for calculating harmonic winding factors and evaluating the average torque is synthesized. The proposed approach is validated through case studies and experimental tests.