Saliency performance investigation of synchronous machines for position sensorless controlled EV drives

In this paper a per unit scale saliency- and saliency shift equation are used to predict the saliency based position sensorless control performance of synchronous machines for EV drives by means of a finite element package. These equations are used in a comparative study of various types of synchronous machines. The machine drives investigated and compared are a reluctance synchronous machine (RSM) hybrid EV drive and two variable gear RSM EV drives. Also included in the investigation are two field intensified permanent magnet (FI-PM) EV drives with asymmetric rotors, one FI-PM machine with a symmetric rotor and one field weakening interior permanent magnet drive. The saliency shift of the different FI-PM machine rotor topologies are also investigated. Closed loop saliency based position sensorless control shows startup torque capabilities of up to 304 Nm of a 32 kW 6-pole RSM. The RSM EV machine is used to investigate possible design modifications to improve on the saliency ratio and shift of synchronous machines.