Current model-based sensorless drives of salient-pole PMSM at low speed and standstill

For all the sensorless drives of the permanent magnet synchronous motor (PMSM), the major problem exists in their low-speed operation. This paper gives a solution to this problem by using a salient-pole PMSM. At low speeds, including zero speed, the rotor position and speed can be estimated by the current response of the voltage pulse, which is intermittently applied to the current minor loop. The current response is position dependent, because the winding inductance is a function of the rotor position. By using the relation between the current response and the rotor position, the basic algorithm of the sensorless drive can be developed. Experimental results from a six-pole 1500 RPM 1.5 kW test motor have proved the stable sensorless drive characteristics below 50 RPM, including zero speed, under 0%-100% loaded conditions.