Sensorless Capability of an Interior Permanent Magnet Synchronous Machine with a Short-Circuited Rotor Winding

Sensorless position estimation based on signal-injection methods always requires a resistance-or inductance-based anisotropy. One way to influence the differential inductances of an electrical machine is the use of a short-circuited electrical winding on the rotor surface. This method is applied to an interior permanent magnet (IPM) machine in this paper. In order to investigate the suitability of a short-circuited rotor winding to improve the sensorless capability of an IPM machine, an optimized rotor concept is derived and investigated by a non-linear machine model. To verify these findings, the presented machine was built and measured. The measurement results are in good agreement with the simulations and show clearly how a short-circuited rotor winding increases the magnetic saliency for the test signal and in consequence, leads to a significant reduction of the estimation error.