On selection of rotor support material for a ferrite magnet spoke type traction motor

Interior permanent magnet motors with ferrite magnets and distributed windings can be a cost effective alternative to rare-earth magnet based motors for demanding applications such as automotive traction. Among different rotor topologies, the spoke type may be preferred, due to its advantages for high flux concentration and resistance to demagnetization, when carefully designed. When high speed operation is required, to increase the power density of the motor, the spoke type rotor must be comprised of two sections: a) the ferromagnetic rotor pole to provide the path for the magnetic flux, and b) the non-magnetic rotor support to provide the structural integrity. In this paper, the multiphysics and cost implications of the rotor support material, as part of a high performance ferrite magnet traction motor, are reviewed, and an optimal selection with respect to those criteria is proposed.