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

For the sensorless drives of the permanent magnet synchronous motor (PMSM), the common problem is in the low speed operation. This paper gives a solution for this problem by using the salient-pole PMSM. At low speeds including zero speed, the rotor position and speed can be estimated by the current response for the pulsewise voltage 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 given. The experiments using a 6-pole, 1500 r/min, 1.5 kW test motor have proved the stable sensorless drive characteristics below 50 r/min including zero speed under 0-100% loaded conditions