Position estimation scheme of single-phase hybrid SRM using back-EMF

This paper presents a novel scheme to estimate the rotor position of a single-phase hybrid switched reluctance motor (HSRM). The proposed method uses the differential of back-EMF within a position region to estimate rotor position. By detecting the crossing-zero signal of back-EMF differential value, the minimum position of back-EMF corresponding to an absolute rotor position can be captured and used for position estimation four times in every mechanical rotation. In this way, a sensorless operation with adjustable turn on/off angle can be achieved without substantial computation. For the starting, two current comparators are adopted. One of them is used to limit the maximum current, the other is to detect the turn-off position at first electrical cycle. The experimental verification using a prototype drive system is provided to demonstrate the viability of the proposed sensorless scheme.