Magnetic Gear: Radial Force, Cogging Torque, Skewing, and Optimization

Magnetic gears are able to transmit torque between an input and an output shaft without mechanical contact. As for electrical drives, torque density, acoustic noise, and torque ripple are of primary concern. This paper describes the influence of the pole numbers on the radial forces and the cogging torques. We show how continuous and discrete skewing can suppress torque harmonics effectively. Further, we investigated different simulation modes for magnetic gears using finite-element software. A multiobjective optimization was conducted to find a Pareto-optimal magnetic gear, whose cogging torque was minimized by skewing one rotor. Finally, we present a prototype with a gear ratio of 1:21, and compare finite-element results with the measurements of unskewed and skewed magnetic gears.