Sensorless control of a SRM at low speeds and standstill based on signal power evaluation

The switched reluctance motor (SRM) has gained considerable attention mainly because of its low production costs, which result from its simple structure. To increase its simplicity further, research has been done to replace the regular control, which needs a position sensor, with sensorless control. To date most papers on the sensorless control of a SRM have dealt with the running machine and little attention has been paid to very low speeds or standstill. This paper presents a method which is designed to estimate the rotor position at low speeds and at standstill. The method uses a sinusoidal high frequency (600 Hz) current signal which can be injected into the motor by the converter. The voltage signal which depends on the rotor position is measured and its signal power is evaluated. Thus the rotor position can be estimated. Practical results are presented demonstrating the feasibility and accuracy of this method.