New approach for the low speed operation of the PMSM drives with rotational position sensors

A new approach to the position sensor elimination of permanent magnet synchronous motor (PMSM) drives for low speed operation is presented in this paper. Using the position sensing characteristics of the PMSM itself, the actual rotor position as well as the machine speed can be obtained even in the transient state. Since the essential back-EMF information is obtained from the direct measurement during a special test cycle named `MCDI´, the operating speed range of the sensorless drives can be extended to 10 RPM. Moreover, the chronic starting problem of the PMSM drives can be simply settled by the proposed algorithm. In order to verify the feasibility of the proposed scheme, experimental results on the low speed range about 10-100 RPM are also presented