Performance evaluation of five-phase outer-rotor Permanent magnet vernier machines

Abstract

With ever-increasing concerns on clean environment and global warming, there is special interest in electric vehicles (EVs) to be used instead of conventional vehicles with internal combustion engines (ICEs). Among competing machine types, permanent magnet (PM) brushless motor is the most commonly employed motor type for this technology due to their important advantages of high power density, high efficiency. Furthermore, higher fault tolerant capability at low speed which can be achieved by combining a coaxial magnetic gear (MG) with an outer rotor PM brushless machine resulting in a Permanent magnet vernier (PMV) machine. The performance of a fault-tolerant PMV machine depends on the proper selection of slots/poles combination which offers low speed/high torque operation and eliminates the effect of low order harmonics in the stator magneto motive force and hence reduces the vibration and stray loss. In this paper, three outer rotor five-phase PMV machines with the same dimensions and different slots/poles combinations are designed. The number of flux modulating poles (FMPs) is optimized to obtain better torque curves and efficiency. A simulation study is carried out using 2D-Finite element method (2D-FEM) to compare the performance of the three machines at rated condition.