Two-phase SRM with flux-reversal-free stator: Concept, analysis, design, and experimental verification

The demand for high-efficiency electric motor drives at low cost is increasing, particularly, in high-volume applications, such as household appliances. Single- and two-phase machines are viable under such constraints. Between them, two-phase switched reluctance motor drives are preferred from the viewpoint of performance. This paper presents a novel two-phase switched reluctance machine (TPSRM) that is conceived for high-efficiency operation and full-load starting performance for any initial rotor position. The principle of operation of the proposed TPSRM and its unique features such as the flux-reversal-free stator for reducing core losses, the utilization of only two thirds of the stator core for each phase operation, and the resulting low noise are presented. The machine is analyzed with the 2-D finite-element analysis method. Self-starting in the proposed machine is developed with rotor pole shaping, and a unique technique to provide the desired torque characteristics is described. The effect of varying pole arcs, the number of turns per pole, asymmetric pole placement, and rotor pole shaping on torque and phase inductance is evaluated to find the best machine dimensions for a required performance as well as to understand qualitatively the influence of each variable on the machine performance. Experimental results from a 2.2-hp laboratory prototype correlate the performance predictions and validate the claims for this novel TPSRM.