Cogging Torque Reduction of Halbach Array Permanent Magnet Motor Based on Magnetic Field Energy Equivalence

In this paper, the magnetic field energy equivalence concept is incorporated into rotor topology design to reduce the cogging torque for the permanent magnet (PM) motor. The effect of the magnetization direction and the width ratio of the Halbach array PM on cogging torque is investigated. Firstly, based on magnetic field energy equivalence principle, the magnetomotive force (MMF) and magnetic permeance characteristics of the Halbach array PM motor are analyzed, and then the analytical expression of cogging torque is derived. After qualitative analysis, the magnetization direction and PM width ratio are identified and optimized as key parameters for reducing the cogging torque. Through the rational design of key parameters, the PM MMF characteristics of the Halbach array PM motor are changed, significantly contributing to the cogging torque reduction. Then, electromagnetic performance comparative analysis of traditional radial and Halbach array PM motors are carried out by finite element analysis (FEA). Finally, the theoretical analysis and the FEA results verify the effectiveness of the magnetic field energy equivalence principle for cogging torque reduction of the proposed Halbach array PM Motor.