Influence of stator saturation on the differential inductances of PM-synchronous machines with concentrated winding

For sensorless position detection of permanent magnet synchronous machines at very low speed and standstill, signal injection methods are commonly used. As a prerequisite these so called saliency-tracking methods require a differential magnetic anisotropy of the machine, which is both position and load dependent and thus varying during operation. So the performance of sensorless operation strongly depends on the machine design. To investigate the influence of the stator saturation a machine model based on a magnetic equivalent circuit is presented in this document. This model is then used to analyze the differential inductances of a machine with concentrated windings. The results show that for some angles of the current vector the inductances do not vanish even for high currents. This phenomenon is explained by analyzing the flux paths.