An accurate position estimation method for switched reluctance motor drive

In this paper a low-cost sensorless control strategy of SR motor is proposed. The static flux-linkage characteristics of the motor are used for estimating the position. A number of discrepancies between the static and the dynamic characteristics of the motor are explained. In this paper the issues regarding eddy effects and mutual inductances in both static and dynamic conditions, and their influence on position estimation, are discussed. Finally, the means of accurate estimation are proposed. Choosing the central region of flux linkage characteristics, adopting single-pulse operation throughout the speed range by means of voltage control, selecting appropriate phase for estimation, and introducing a correction factor ´K_c´ (a function of voltage, speed and load) on static flux linkage, the sensorless operation is achieved. To implement the algorithm a TMS320c50 DSP platform is used. The controller was tested on a 5 hp 8/6 OULTON motor. Results of tests, and accuracy of position estimate are presented. The accuracy of estimated position is found to be within ±1°. The proposed method uses only one phase voltage and one phase current for estimating the position.