Field-Harmonic-Oriented Design of Vernier Permanent Magnet Machine Towards High Torque Density and Low Torque Ripple

Vernier permanent magnet machine (VPMM) has been a promising candidate for low-speed large-torque applications owing to high torque density based on multiple-magnetic field-harmonics working principle However, rich field harmonics also cause large torque ripple, meanwhile the regular reducing methods will also undermine torque density. In this paper, the field-harmonic-oriented design approach is proposed for the VPMM towards high torque density and low torque ripple. Based on the permeance unit model, the mapping relationship between torque output and field harmonics is built. Explicit design regulations are established for the airgap structure so as to modulate the optimal field harmonics composition. Via the proposed method, a surface-mounted VPMM is purposely designed and the electromagnetic performance is verified by FEA. Finally, a prototype of the proposed machine has been manufactured and tested. Both analytical and experimental results validate the feasibility of the proposed design method.