Estimation of Motor Winding Inductances based on a Sensorless Technique for the Observation of the Rotor Position

Abstract

This paper analyses the characterization of the electrical symmetry of ironless motor windings by using a technique that has been typically used for sensorless control of motors. In particular, such technique allows the observation of the rotor position of Permanent Magnet Synchronous Machines (PMSMs). This method has been extended to a test-bench application for measuring the rotor dependent inductance ratios in the individual strands of the machine. After an introductory explanation of the measurement principle, the developed electrical circuit as well as the mechanical construction of the test-bench are presented. Moreover, with regard to a suitable design of the magnetic circuit, measurement results on selected ironless windings are discussed. A first evaluation of the results shows that significant information is obtained concerning the winding symmetry especially considering the high repeatability of the chosen measurement technique. Furthermore, the latter allows short circuits within the motor winding to be detected.