Two Phase SRM With Flux Reversal Free Stator: Concept, Analysis, Design and Experimental Verification

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 viewpoints of performance. This paper presents a novel two phase switched reluctance machine (TPSRM) 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 to reduce core losses, utilization of two thirds of the stator core only for each phase operation, and resulting low noise are presented. The machine is analyzed with two dimensional 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, number of turns per pole, asymmetric pole placement and rotor pole shaping on torque and phase inductance are 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