Fractional-Slot PMSMs With One Coil Parallel Branches Made Phases—Part 2: Circulating Harmonic Current Rejection Potential

Abstract

The paper is aimed at a class of fractional-slot permanent magnet-synchronous machines (FSPMSMs) equipped with phases made up of one coil parallel branches, with emphasis on their potential to reject the circulating harmonic currents. Following the identification and topological characterization of this class of machines treated in Part 1, the star of slots approach is extended to the investigation of their back-EMF harmonic content, and the possible resulting circulating harmonic currents. It is found that all identified candidates exhibit the potential to reject the circulating harmonic currents. A case study dedicated to a candidate equipped with three phases made up of six parallel branches of one coil each, is treated. Following an analysis of its back-EMF harmonic content, the torque-speed characteristic is analyticallypredicted and validated by 2D finite element analysis and by experiments. The study is achieved by a special attention paid to the iron loss and thermal analysis.INDEX TERMS Fractional-slot PM synchronous machines, one coil parallel branches made phases, start of slots approach, back-EMF harmonic content, circulating harmonic currents, torque production, power flow and thermal analysis.