Detection of the rotor position of a permanent-magnet synchronous motor at standstill

This paper introduces a method to detect the rotor position of a three-phase permanent-magnet synchronous motor (PMSM) at standstill. It applies a test voltage pulse between two terminals of the PMSM and measures the voltage response between the free and one of the two connected terminals, from which the initial rotor position is obtained. Being based on the measured voltage response, other than using a current response, this method is less affected by temperature and saturation. In addition, this method does not require the absolute values of L-d and L-q, but only the saliency factor, which can be determined by the maximum and minimum values of the voltage response in a period of 2 pi of the electrical rotor angle. Some experimental results are presented to verify the applicability of the method.