A sensorless switched reluctance drive

There is one drawback in the switched reluctance motor system: the need for rotor position feedback to allow correct phase commutation. This normally involves the use of a position encoder on the rotor, and a number of different types are used ranging from simple single optodetector systems, detecting edges on a vaned disc, to high accuracy resolvers. Whichever encoder is selected, however, will add to the cost of an otherwise relatively cheap motor, will require additional electrical connections, and is a potential source of unreliability, especially if the motor is to be used in a harsh environment. It is therefore highly desirable, and indeed there is commercial pressure, to find some way of detecting a rotor position remotely from the motor and without the need for a rotor position transducer (RPT). This paper introduces one such system, successfully combining two previously reported methods (the low speed diagnostic pulse method by N. Mvungi (1990) and the high speed method by W.F. Ray (1994)) to give robust and reliable operation over a very wide speed range in all four quadrants