A Quantitative Comparison Analysis of Radial-Flux, Transverse-Flux, and Axial-Flux Magnetic Gears

The performances of three types of magnetic gears (MGs), which are radial-flux MGs, transverse-flux MGs, and axial-flux MGs, are quantitatively analyzed and compared using 3-D finite-element method of magnetic field and mechanical motion coupled computation. To fairly compare the torque capability of different topologies of MGs, all the MGs under study have the same gear ratio, the same outer diameter, and the same axial stack length. To maximize the torque density, several important structure parameters are optimized. Scenarios using different iron core materials and different magnetization directions of permanent magnets are also studied. Based on the comparative analysis, appropriate topologies of MGs that can achieve a torque density as high as 198 kNm/m3 are suggested. The results in this paper give a good review of the torque density levels of different MGs, and hence they can be used as application guidelines.