Comparison of synchronous machine designs with displaced reluctance axis considering losses and iron saturation

Synchronous machines with displaced reluctance axis promise improved performance due to the optimized utilization of reluctance and synchronous torque. Their torque characteristics make these machines interesting for applications which mostly require just one operation mode, i.e. motoring or generating, such as traction drives for electric vehicles. First of all, this paper shows that arbitrarily displaced reluctance axes are difficult to realize with pure permanent magnet and pure electrically excited synchronous machines and yield disadvantageous machine properties. In the second part, a hybrid synchronous machine topology which incorporates a displaced reluctance axis is introduced and its conceptual advantages compared to conventional machine designs are shown.