Cost reduction of a permanent magnet in-wheel electric vehicle traction motor

This paper describes a motor for use within the wheel of an electric vehicle. It demonstrates the influence of various rotor parameters on an outer rotor permanent magnet motor (ORPM) with Surface-mounted magnets (SM). The aim of this paper is to reduce the magnet volume, while maintaining the torque performance through the complete operating range. Six different magnet topologies are investigated firstly. Then, Semi Surface-mounted Permanent Magnet (SSPM), I shape tangential PM (IPM) and V shape interior PM (VPM) designs are compared in terms of torque capability at certain magnet volume. The VPM gives highest torque performance. The iron shielding concept in VPM can protect the magnets from the opposing armature flux, thus providing increased resistance to demagnetisation, and hence permitting thinner magnets. Furthermore, a new slot/pole combination with higher torque capability has been studied. However, due to the increased inductance, motor with V shape design needs to work at a poorer power factor and consequently a reduced speed range for a given inverter. Lastly, Cost effective and simple manufacture method of the VPM rotor is also addressed with consideration of mechanical feasibility.