Initial Rotor Position Detection for Surface Mounted PMSM

This paper presents a methodology for determining the initial rotor position of a surface-mounted permanent magnet synchronous motor (SM-PMSM). Due to the lack of magnetic saliency in surface-mounted SM-PMSM, detection of the initial rotor position is challenging. In this paper, a series of positive and negative voltage pulses are applied to the stator windings of a three-phase SM-PMSM. The resulting positive and negative current values and the recorded differences between the peaks are assessed. By using the relation of differences in peak current values and the location of permanent magnets of the SM-PMSM motor, a methodology for the detection of the initial rotor position is developed. Precise estimation of the rotor position at the standstill condition, without using any additional hardware, is the prominent advantage of the proposed methodology. A numerical model for the experimental four-pole SM-PMSM is developed (using Maxwell 2-D) and it is used to verify the magnetic changes during the proposed detection method. It is observed that due to variation of flux linkage, the difference between the absolute value of the peak value changes. Finally, the validity of the presented method is experimentally verified.