Analysis and Design Optimization of a Coaxial Surface-Mounted Permanent-Magnet Magnetic Gear

Xiaoxu Zhang,Zhe Chen,Xiao Liu,Chao Wang

doi:10.3390/en7128535

Abstract

This paper presents the analysis and design optimization of a coaxial surface-mounted permanent-magnet magnetic gear. The magnetic field distribution in the coaxial magnetic gear is calculated analytically in the polar coordinate system and then validated by the finite element method (FEM). The analytical field solution allows the prediction of the magnetic torque, which is formulated as a function of design parameters. The impacts of key design parameters on the torque capability are then studied and some significant observations are summarized. Furthermore, the particle swarm optimization (PSO) algorithm is employed to optimize the studied magnetic gear. Given that the torque capability and material cost conflict with each other, both of them are set as the optimization objectives in this paper. Different weight factors may be chosen for the two objectives so that more attention can be placed on one or another. The results shows that the highest torque density of 157 kNm/m3 is achieved with the consideration focusing on the torque capability only, then the highest torque per permanent magnet (PM) consumption could be improved to 145 Nm/kg by taking the material cost into account. By synthesizing the torque capability and material cost, a 124 kNm/m3 of torque density and a 128 Nm/kg of torque per PM consumption could be achieved simultaneously by the optimal design.

Highlights

Mechanical gearboxes are widely used as the transmission devices connecting electrical machines and loads in low-speed high-torque applications
Reference [16] carried out a comparative study between the non-rare-earth and rare-earth permanent magnet (PM) coaxial magnetic gears, and the results indicate that with emphasis on the cost effectiveness, non-rare-earth PMs are preferred for coaxial magnetic gears, but the torque capability is compromised
This paper has developed an analytical model for the coaxial surface-mounted PM magnetic gear, which presents a good agreement with the corresponding finite element method (FEM) model

Summary

Introduction

Mechanical gearboxes are widely used as the transmission devices connecting electrical machines and loads in low-speed high-torque applications. Cooling and regular maintenance are required, which may further increase the running cost of the mechanical gearboxes. The direct-drive concept, which may directly drive the load by the electrical machine, could avoid the above problems, the accompanying increased volume of the direct-drive electrical machine as well as the increased cost in processing, transportation and installation may limit its applications [3,4]. With the increasing of the power capacity and the decreasing of the rated rotating speed, such as wind power conversion systems, the disadvantages of the above two drive trains may be even amplified [5]

Methods

Results

Conclusion