Operation of a Self-Controlled Synchronous Motor Without a Shaft Position Sensor

The starting operation of a self-controlled synchronous motor without a shaft position sensor is studied. A method which permits the determination of the rotor position at a standstill by voltage sensing is explained. Various forced commutation techniques and starting, strategies are considered. Torque characteristics for natural commutation operation are studied, providing simple formulas with good precision. Experimental results obtained with a prototype drive system are given.