Study of low speed sensorless drives for SPMSM by controlling elliptical inductance

The rotor position sensor is required to control Permanent Magnet Synchronous Motor (PMSM). However, the rotor position sensor, for example, Resolvers or Pulse Generator (PG) have some disadvantages which are an increase of total volume of the motor, fault of power supply lines and signal lines of these sensors, and maintenance. To overcome these difficulties, sensorless control methods have been developed [1-10]. From standstill, Sensorless drive method for saliency PMSMs has been already proposed. However, applying these conventional techniques is not adequate to Surface Permanent Magnet Synchronous Motor (SPMSM) because of a few saliency of SPMSM. This paper proposes a low speed sensorless drive method for SPMSM which has small salient magnets. The low speed range is zero to 2-3% of rated speed. The study proposes the principle of anisotropy of the inductance of SPMSM generated by the d-axis current and magnetic saturation by the magnet flux.