Sensorless Position Estimation of Switched Reluctance Motors Based on Gradient of Phase Current

This paper describes a low cost sensorless switched reluctance motor (SRM) driver system based on gradient of phase current. The sensorless control method uses the change of the gradient of the phase current to detect the rotor position where the rotor pole and stator begin to overlap. At this position, phase inductance begins to increase. Voltage control is used in the zone near the position, and the PWM duty ratio is constant during one electrical cycle. In other zones, traditional hysteresis current control is used. The sensorless control method is simple with only a minimum of extra components, and can operate in a wide speed range. A laboratory prototypes system has been built and tested. Experiment results are also given.