Low Harmonics Design for Modular Permanent Magnet Synchronous Machine Using Partitioned Winding

Modular permanent magnet synchronous machines have received widespread attention due to their high copper filling factor, simple manufacturing, and low cost. However, the armature reaction magnetic field of MPMS machines usually has enormous sub- and high-order space harmonics due to its nonoverlapping concentrated winding structure, thus leading to high losses in both PMs and iron core, local core saturation, and high torque ripple. In this article, a low harmonics design method using partitioned winding structure is proposed based on the airgap field modulation theory. By adopting the proposed method, a 36-slot/42-pole low harmonics MPMS machine is proposed and analyzed by both equivalent magnetic circuit method and finite element analysis. The results show that the nonworking space harmonics are reduced and the effective working harmonics are slightly increased. So the torque ripple and the total loss can be reduced by 50% and 1.35%, respectively, and the efficiency is improved by 0.57%. A prototype machine is built and tested to verify the analysis and finite element analysis results.