Initial Rotor Position Estimation of Single-phase Permanent Magnet Synchronous Motor with Asymmetric Air-gap

This paper presents an initial rotor position estimation algorithm of asymmetric air-gap single-phase permanent magnet synchronous motors without using a hall sensor. Generally, the common problem associated with the sensorless drive is the starting operation. Most sensorless control methods are based on back-EMF. However, when motor is at standstill or low speed, the back-EMF is too small to detect rotor position. Therefore, high frequency injection methods are widely used in the standstill or low speed region. In case of the SP-PMSM, when high frequency signal is injected to asymmetric air-gap single-phase PMSM motors, flux saturation is not occurred at air gap unlike 3-phase PMSM. Due to alternating magnetic field at the air-gap, initial rotor position of the SP-PMSM is hard to be estimated. As a result, in this paper, DC offset voltage is added to the high frequency injection signal to generate flux saturation at the air-gap of the SP-PMSM. The several experimental results show that the proposed algorithm is effectiveness and usefulness for SP-PMSM with non-uniform air-gap.