Improvement of the accuracy and speed range in sensorless control of switched reluctance motors

In this paper, modulation based sensorless control of switched reluctance motors is presented. The basic idea is to inject sensing signals into one of the nonconducting phases and obtain the rotor position indirectly through signal measurements. A computer model has been developed to analyze and design the hardware for the sensorless scheme. The frequency of the sensing signal is chosen based on the required resolution of rotor position at rated speed. The high frequency effects of the sensing signals on the self-inductances of the phases have been considered while designing the scheme. Based on the simulation results, the sensorless circuit is calibrated so that different control angles, viz. turn-on and turn-off angles can be realized. Since the control angles can be varied, real time optimization, self-tuning control etc. can all be carried out. Detailed design procedure of the sensorless scheme along with the practical considerations are presented in the paper. The proposed sensorless control has been implemented on a 6/4, 500 W drive system and the simulation results are verified. The experimental results obtained for a wide speed range with different loads and control angles are also presented