Permeance Reconfiguration in Flux Modulation Permanent Magnet Machines With Transcription Waveform Method

Flux-Modulation Permanent Magnet (FMPM) machines exhibit high torque density due to the multi-harmonics utilization. The nonuniform permeance helps to enhance torque density, but there is a lack of theoretical guidance for establishing optimal permeance. In this paper, a permeance transcription waveform (PTW) is proposed to clarify the influence of inhomogeneous permeance on magnetic field harmonics. Firstly, the straight-tooth structure and split-tooth structure are analyzed to elucidate the impact of permeance distribution on torque performance. Then, a method for calculating harmonic contributions based on energy analysis is proposed to determine the quantity and phase of permeance harmonics. Integrated with permeance unit design, harmonic amplitude allocation is optimized to derive the optimal permeance structure. Finally, experimental results and simulation performance comparison verify that the proposed FMPM machine with nonuniform permeance achieves higher average torque than the conventional FMPM machine.