Comparative study of five-phase in-wheel fault-tolerant modular PM machines with different number of rotor poles

The performance of fault-tolerant modular PM machines depends on the proper selection of the pole and slot numbers which results in negligible coupling between phases. The preferred slot and pole number combinations eliminate the effect of low order harmonics in the stator MMF and thereby the vibration and stray loss are reduced. In this paper, three machines, with an external rotor design and identical machine dimensions, are designed with different slots per phase per pole (SPP) ratios. A simulation study is carried out using FEA to compare the performance of the three designed machines in terms of machine torque density, ripple torque, core loss, and machine efficiency. The simulation study is extended to study the performance under fault conditions.