Analysis and Benchmarking of Radial Flux Cycloidal Magnetic Gears with Reduced Permanent Magnet Piece Count Using Consequent Poles

Magnetic gears employ magnetic fields, rather than teeth, to perform the gearing action. At large gear ratios, cycloidal magnetic gears (CyMGs) can achieve higher torque densities than the more common coaxial magnetic gears. This paper compares CyMG topologies with consequent pole (CP) rotors against CyMGs with more conventional surface permanent magnet (SPM) rotors. CyMGs with CP rotors require less PM pieces than CyMGs with SPM rotors, which may simplify manufacturing. Each topology is optimized using a genetic algorithm with 2D finite element analysis (FEA). The simulation results demonstrate that CyMGs with CP rotors achieve lower VTD values than CyMGs with SPM rotors. However, if using a CP inner rotor eliminates the need for a PM retention sleeve and enables the use of a smaller effective air gap, CyMGs with CP rotors can achieve higher PM STs at high gear ratios than CyMGs with SPM rotors. CyMGs with CP rotors generally experience similar perpendicular magnetic forces and slightly higher eccentric magnetic forces, relative to CyMGs with SPM rotors. The optimal 2D designs are further investigated using 3D FEA, and, within this design set, the CyMGs with CP rotors experience more significant end effects than the CyMGs with SPM rotors.