Cogging Torque Reduction in Hybrid-Excited Axial Field Flux-Switching Fault-Tolerant Machines

Hybrid-excited axial field flux-switching fault-tolerant machine (HEAFFSFTM) is a novel permanent magnet machine. It offers several performance advantages which make it an interesting candidate for electric vehicles (EV), including a high torque density, high degree of fault-tolerance capability and wide operating speed range. However, this machine has a higher cogging torque than many other topologies of permanent magnet machines due to its doubly nature. In order to ameliorate this drawback, the influences of geometry and design feature on cogging torque are investigated. Methods for reducing cogging torque are studied with three-dimensional finite element analysis, special 3-D JMAG package and supported by experimental measurements on an optimized prototype. The analysis demonstrated that for this topology of machine, the cogging torque reduction achieved by rotor tooth slotting, optimizing rotor tooth shape and angular offsetting of stator are more pronounced than those achieved through the selection of rotor pole numbers, rotor skewing and angular offsetting of rotor.