Cycloidal Reluctance Magnetic Gears for High Gear Ratio Applications

Abstract

At high gear ratios, surface permanent magnet (SPM) cycloidal magnetic gears (CyMGs) can achieve higher torque densities than SPM coaxial magnetic gears (CoMGs). This article introduces the radial flux reluctance CyMG (Rel CyMG) topology and its operating principles. The Rel CyMG replaces the permanent magnets (PMs) on an SPM CyMG’s inner rotor with salient teeth. Additionally, the Rel CyMG only requires half of the SPM CyMG’s outer rotor PM count to achieve the same gear ratio, which simplifies assembly and allows the use of wider magnets. This may improve high gear ratio designs’ manufacturability. A genetic algorithm (GA) was used with 2-D finite element analysis (FEA) to optimize Rel CyMGs, SPM CyMGs, and SPM CoMGs and demonstrate that SPM CyMGs significantly outperform the other topologies at higher gear ratios in terms of specific torque (ST) and PM ST. However, Rel CyMGs outperform SPM CoMGs at higher gear ratios, with respect to ST and PM ST. Rel CyMGs also eliminate the need for a PM retention sleeve and potentially enable the use of smaller air gaps, which can allow them to achieve slightly higher PM STs than SPM CyMGs at ultrahigh gear ratios. Employing Halbach arrays significantly improves both CyMG topologies’ ST.