A PMSM with Enhanced Anisotropic Rotor Configuration for Sensorless Operations

Sensorless control technologies based on rotor saliency may not operate well due to the effect of magnetic saturation. In this work, a rotor backend (RB) is attached to an existing rotor structure of a permanent magnet synchronous motor (PMSM) to enhance anisotropic features. The geometry of the RB is further optimized to achieve greater current amplitude induced by the RB saliency modulation. The phase sequence direction of the modulation is not electrically synchronized with the rotor reference frame. A fractional slot/pole combination is selected and analyzed to strengthen the saliency modulation signal. Hence, the sensorless techniques will be immune to saturation effect in highly exploited machines. Both low and high-speed performance of the proposed method is verified through the experimental tests. It is demonstrated that the position estimation using saliency modulation of the RB is unaffected by machine saturation due to its electrical asynchronous property.