Analysis and Optimal Design of Hybrid Magnetic Circuit Reluctance Direct Drive Motor

Abstract

Reluctance direct-drive motors have become a hot research topic in recent years due to their high torque density, therefore, this paper proposes a novel hybrid magnetic circuit reluctance direct drive motor (HMRM) to meet the requirements of high torque density in low-speed and high-torque application. The stator and rotor of the motor are all convex pole structure. The stator teeth are grooved, in which permanent magnets with tangential magnetization are placed. The rotor is a simple reluctance structure. With this cleverly designed stator and rotor structure, the air gap magnetic field is modulated to improve the torque density of the motor. Firstly, the structure and working principle of the motor are introduced, and the expression between air gap density and torque is derived based on the magnetomotive force permeance model, which is utilized to analyze its working harmonics to enhance the torque density. Secondly, a multi-objective optimization model is proposed to the proposed HMRM, where the design objective of maximum torque and minimized torque fluctuation selected and optimized with multi-objective genetic algorithm method. Finally, a finite element model of the HMRM is developed and its performance is compared with that of the conventional permanent magnet motor. The results show that the proposed HMRM has greater torque density, higher permanent magnets utilization, and lower motor cost. The research theory and design methodology in this paper are significant in promoting the application of hybrid magnetic circuit reluctance motors in direct drive systems.