Torque Production in Triply-Excited Magnetic Gears

Magnetic gears (MG) are an important development to improve on the disadvantages of their mechanical counterparts. MGs have multiple topologies with each finding their suitable application. The triply excited magnetic gear (TEMG) is one such topology with interesting possibilities. This topology has an extra set of permanent magnets (PMs) in between the ferromagnetic modulators in addition to the PMs located in the inner and outer rotor. The TEMG topology has multiple variations with respect to PM placements; the torque production in three such variations is studied and compared with the conventional coaxial MG (CCMG). Different geometric parameters are varied and the various topologies are optimized for maximum volumetric torque density (VTD) and permanent magnet specific torque (PM ST). The torque generated by these optimized models is compared, using the finite-element method (FEM), to verify the advantages and disadvantages of the TEMG topologies. The torque production due to the PMs located in between the modulators is minimal compared to the torque produced due to the PMs present in the other two rotors. Thus, the CCMG generally outperforms the TEMG topologies.