Waveform detection technique for indirect rotor-position sensing of switched-reluctance motor drives. Part 2: Experimental results

Abstract

A digital controller based on the waveform detection technique which uses the current chop risetime in the active phase for monitoring rotor position is inplemented. The controller is applied to a 4 kW SR motor and its limits of operation examined. Experimental results show that it is possible to operate the SR motor with indirect rotor position sensing and achieve output torque and system efficiency similar to those achievable from commercially available SR drives using direct rotor-position sensors. Back EMF has significant effect on the phase current rise and fall times even at few hundred rev/min, and must therefore be taken into account when using the technique for position detection. At high speeds as no chopping takes place, the initial current rise-time is monitored for position detection. The effect of varying detect time on the operating speed at constant load torque, variation of load torque at constant detect time and variation of average phase current level were studied through experiment observations.