Design of high performance traction motors using cheaper grade of materials

Rare earth permanent magnet motors are amongst the most popular choices for traction applications due to their high power density as well as efficiency. However, due to the expensive rare earth materials, designs with cheaper magnet grades including ferrites or NdFeB magnets with less rare earth content have, recently, gained popularity. Furthermore, despite the unanimous application of copper as winding materials for electric machinery, aluminium may serve as a substitute which may bring both cost and recyclability advantages. The challenges involved with the use of poorer grade magnets involve an approach to overcome the low power density and efficiency, as well as dealing with the higher risk of demagnetization for these designs. With regards to aluminium windings, care must be taken to avoid excessive temperature rise during the transient peak operation, as well as a thermo-mechanical failure of the aluminium to copper terminations due to the continuous and cyclic thermal variation. In this paper, a high performance spoke type motor consisted of ferrite magnets and aluminium windings is reviewed, and some analyses with regards to the thermal performance are provided. Furthermore, an alternative rotor design with a single piece topology is assessed for an electric boat traction application, where, for the first time, the use of HDDR recycled NdFeB magnets applied to an electric motor is examined.