Topologies and performance study of a variety of coaxial magnetic gears

This study aims to provide a comprehensive study of various magnetic gears (MGs) with simple coaxial radial flux structure. A total of 15 topologies are first introduced, by either using various rotor structures or adding extra permanent magnets (PMs) on the magnetic modulation ring. Then, all topologies with ferrite magnets are parametrically optimised, aiming to compare and evaluate the performance of these MGs. The results show that the proposed MGs with dual consequent-pole PM rotors exhibit a higher torque density than the conventional coaxial MG. Therefore, magnetic field distribution, torque-angle characteristic and on-load torque performance of these promising MGs are analysed in detail, revealing their inherent superiorities. In addition, influence of magnet material on the MG performance are investigated with emphasis on the torque density and cost effectiveness. Finally, two MG prototypes are fabricated and tested to validate the analysis.