Sensorless operation of the SR motor with constant dwell

Sensorless control of the SR (switched-reluctance) motor is proposed in which the rotor positron is estimated from the freewheeling (tail) current. The analytical design and experimental verification of the proposed control structure are given. It is concluded that stabilization of the SR motor running without position sensor can be done by affecting the pulse frequency by the freewheeling (tail) current or the initial current slope in a cheap and effective way. Analysis of the experimental current waveform shows that freewheeling current feedback gives better results for high torques, while slope feedback performs better for low and negative torques. The control scheme employs freewheeling current feedback and varies the advance angle according to the load changes. The scheme was tested through measurements on an experimental drive and showed stable operation in the whole monitoring regime.