Contemporary finite element analysis techniques for permanent magnet brushless DC machines, with application to axial flux traction systems for electric vehicles

This paper begins with a summary of current issues regarding EVs and their traction systems, and develops a case for the permanent magnet brushless DC machine. This is followed by a tutorial on contemporary finite element analysis techniques as applied to such machines. Validation studies are presented comparing several techniques of analysis and laboratory measurement on important parameters such as cogging torque and back EMF waveforms, which are additional to the more traditional flux density computations. A different approach to the measurement of back EMF waveforms via force calculations is introduced. Results are discussed for a specific axial flux machine which is being developed for traction applications. In particular, the static and dynamic axial forces are computed, which are important for the mechanical design of this machine which features real time mechanical gap variation, to provide flux weakening.