Synchronous reluctance motor with concentrated windings for IE4 efficiency

This paper investigates the applicability of fractional-slot concentrated windings to Synchronous Reluctance Motors for industry applications. Tooth-wound winding arrangements are attractive for the industry due to their lower cost of manufacturing, but when associated to a synchronous reluctance rotor they tend to lower the output torque and power factor of the machine significantly, and to excite high values of torque ripple. The proposed analysis shows that after design optimization one synchronous reluctance machine with concentrated windings can reach the IE4 (super-premium) efficiency class within the same frame of a distributed-winding synchronous reluctance machine of the same size. Moreover, the paper demonstrates that the synchronous reluctance rotor must be purposely redesigned for the new stator, when passing from distributed to concentrated windings, for the sake of torque ripple mitigation. A step by step design procedure is provided, supported by finite-element analysis and experimental results.