Saliency investigation of switched-flux PM brushless AC machine for saliency-tracking-based sensorless control

This paper investigates the saliency in switched-flux permanent-magnet (SFPM) brushless AC (BLAC) motors. In order to use the method of high-frequency pulsating vector voltage carrier signal injection-based sensorless control techniques, the machine saliency is essential. However, the machine saliency behavior is complicated in real SFPM machines since it is dependent on the load condition. Furthermore, there may exhibit multiple saliencies due to the non-sinusoidal spatial distribution of machine reluctance. Saliency ratio and feasible region are usually used to describe the machine saliency level. It varies with fundamental excitation due to the magnetic saturation. Two simplified experimental procedures are employed for practical testing of saliency investigation in this paper, which could easily measure and obtain the machine saliency information without any knowledge of machine parameters. The experimental results show that the prototype machine has both primary and secondary (multiple saliencies) saliencies. The performance of rotor position estimation is implemented based on sensorless control at low and zero motor speed.