Parameters Analysis and Optimization Design for a Concentric Magnetic Gear Based on Sinusoidal Magnetizations

Concentric magnetic gears hold a promising future in the field of low speed and high torque. To obtain a sinusoidal distribution of air gap magnetic field, in this paper, exact 2-D analytical method is proposed to calculate the magnetic field distribution in a concentric magnetic gear with Halbach permanent-magnet arrays, and analyzes the relationship between the parameters and maximum static torque, the parameters include width of modulating ring core, height of modulating ring and thickness of outer rotor yoke. Compared air-gap magnetic field distributions computed by the analytical method with those obtained from the 2-D finite-element method (FEM), the analytical and the FEM results are in good accordance, which proves the proposed method is correct and effective. According to the results of parameters analysis, the concentric magnetic gear prototype is produced, which the numbers of pole pairs on the inner and outer rotors are 4 and 17, respectively. The test results show reasonable structural parameters can improve the torque density of magnetic gears, and the design of magnetic gear provides a useful reference.