FEM based analysis of the impact of temperature on the stability range of anisotropy based encoderless control schemes

Anisotropy based encoderless control methods are using the magnetic saliency of an electrical machine in order to determine the actual rotor position and rotor speed. The saliency can either be caused by the geometry of the rotor or by local saturation appearances due to the rotors or stators permanent magnets. Stability is a known issue in the field of anisotropy based encoderless control, the authors in [1] therefore developed three criteria which have to be fulfilled by the machine. The fulfillment of the criteria guarantee, that the anisotropy based control algorithm operates stable and the machine is observable. This publication will investigate the impact of temperature on an adapted stability factor compared to the one defined in [1]. The investigation for the Interior-Permanent-Magnet-Synchronous-Machine (IPMSM) with distributed windings was done by means of finite element simulation (FEM). It will be shown that the area of stable operation is changing with temperature due to the changing properties of the motors materials.