Impact of Dwell Angle on the Electromagnetic Torque Ripplesof the Switched Reluctance Motor

Abstract

Switched reluctance motors (SRM) are emerging as promising competitors to the vector-controlled induction motor (VCIM) drives and permanent magnet (PM) motor drives in the variable-speed drive market owing to their robust nature coupled with low cost, simplicity, and capabilityto operate in harsh environments. They are also suitable for nuclear and aerospace applicationsdue to their low inertia and capability to be fed from a dc supply through a simple power converter.The principle of torque production in SRM makes rotor position information mandatory foreffective control of the drive. The torque produced by any particular phase of the SRM isdependent upon the exciting current and the period during which the current is carried by thatphase winding. The conduction period of any particular phase is termed as dwell angle whenit is specified in terms of rotor angular position. In the present work, the SRM operation has beenanalysed in sensor mode and in sensor-less mode, paying special attention to the relationshipbetween dwell angle and output torque ripple. The performance has been studied for differentvalues of dwell angle and the resultant torque profile has been analysed. From the analysis, amethodology has been devised to deduce an appropriate value of dwell angle for minimising thetorque pulsations, given the values of speed and load torque, thus improving the performanceof the SRM drive.