Inverter topologies and current sensing methods for short pitched and fully pitched winding SR motors

Abstract

By far the most common inverter topology used with switched reluctance machines is the asymmetric half bridge (AHB). While many other topologies have been proposed, only this inverter allows full independent control of the unipolar currents desired in each phase. This paper explores the use of inverters based on the three phase bridge topology and demonstrates their suitability for both the short pitched winding and fully pitched winding switched reluctance machine. Both machine and power electronic efficiencies are compared so that the benefits in terms of pure technical performance and cost can be assessed. Current sensing arrangements are also examined and results from a prototype drive demonstrate the effect that the number and position of sensors have on the ability to control the current to the desired value. The impact on the cost of the power electronics is assessed and a comparison is made with the induction motor drive in terms of peak VA, RMS and mean device current.