Self-trained commutation algorithm for an SR motor drive system without position sensing

For a variety of reasons, eliminating the rotor position sensor typically used to operate a switched reluctance (SR) motor is desirable. In this paper, the authors describe a method for the commutation of an SR motor requiring no rotor position sensor and no detailed prior knowledge of the motor's magnetic characteristics. The method employs a calibration routine to learn the magnetization characteristics of each motor phase at its aligned position, From this information, the flux-current characteristics at some appropriate switching angle can be approximated. Commutation is accomplished by estimating the flux-linked in an active phase and comparing the estimate to the flux approximated for the switching angle. This method is particularly well suited for relatively heavy duty loading, such as a fan. Experimental results are presented which compare the position sensorless technique to a conventional control which uses position feedback.