The Status of Indirect Rotor Position Sensing in SR Drives

The performance of Switched Reluctance (SR) motor drive systems using rotor position transducers has been satisfactory, but the potential of SR drives for providing economical, robust, compact and reliable drive systems which can operate in harsh environments, has made the development of sensorless system desirable. A system which can detect rotor position without a conventional position sensor should avoid the above limitations. Furthermore, the detection system can reside with the control electronics board away from the hostile environment in which the motor may have to be installed. There are various methods of sensorless rotor position measurement developed over several years of research and each of the methods has its own limitations and drawbacks. Much recent and current research is directed at determining rotor position from winding magnetisation data. These magnetisation data either normally available during actual phase energisation or they are specially injected for the purpose of sensorless position estimation. It is the aim of this paper to discuss these sensorless rotor position measurement methods and their limitations.