Unbalanced magnetic force analysis and harmonic optimization of flux switching machine based on stator axial partition

Flux switching permanent magnet (FSPM) machines with odd rotor teeth exhibits significant vibration caused by the unbalanced magnetic force (UMF). This paper proposes a stator axial partitioned FSPM (SAP-FSPM) machine, which can effectively eliminate the UMF, and introduces the UMF suppression principle for the first time. Moreover, the harmonic characteristics of the SAP-FSPM are utilized to achieve rapid optimization. Initially, the UMF suppression mechanism in SAP-FSPM is investigated using magnetic field modulation theory. Subsequently, by analyzing the harmonic components of air gap flux density, cogging torque, and back electromotive force (EMF) of both the SAP-FSPM machine and its two modular parts, we show that these harmonic components either cancel out or superimpose. Based on the above analysis, a method of harmonic optimization for one of the modular parts is proposed to optimize the SAP-FSPM, which transforms the 3D optimization problem into 2D, overcoming the time-consuming nature of traditional 3D optimization. The finite element (FE) simulation shows the effectiveness of the proposed optimization method. Finally, a prototype was fabricated for comparison and validation with the conventional FSPM machine.