Fractional-Slot PMSMs With One Coil Parallel Branches Made Phases—Part I: Investigation Study

Abstract

This work proposes an approach to design fractional-slot permanent magnet synchronous machines (FSPMSMs) equipped with phases made up of one coil parallel branches. These machines exhibit attractive potentialities, especially their enhanced open-circuit fault tolerance capability. Beyond their intrinsic fault tolerance, an open-circuit affecting the targeted topologies leads to a torque step-down limited to the one developed by the concerned coil rather than the torque produced by the total phase in FSPMSMs equipped with phases made up of series-connected coils. Furthermore, these topologies are suitably-adapted to low-voltage power supply that makes them viable candidates in automotive applications. This potentiality is by far vital in battery electric vehicles with the risk of electrocution in case of accident totally-eradicated thanks to the reduction of the DC bus voltage. Part 1 of the developed work is aimed at a star of slots-based identification and topological characterization of the FSPMSMs enabling the arrangement of the armature phases according to one coil parallel branches. The study distinguishes the topologies with odd and even number of phases, arranged in single-and double-layer slots. A case study is treated using a 2D finite element analysis and validated by experiments.INDEX TERMS Fractional-slot permanent magnet synchronous machines, phases arranged in one coil parallel branches, start of slots approach, odd and even number of phases, single-and double-layer slots.

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

“…From a fundamental point of view, by connecting in parallel magnetically-coupled circuits, the first issue, that comes in mind, is the possible circulation of harmonic currents in the loops resulting from the parallel connections of these circuits. Such a problem concerns the FSPMSM candidates identified in [11]. Indeed, these have been selected on the basis that all harmonic back-EMFs of rank p (fundamental) induced in the coils assigned to each phase are identical in magnitude and have similar or opposite phases.…”

“…In what follows, the FSPMSM topologies, enabling the one coil parallel branches made phases, identified in [11], are systematically re-investigated with emphasis on their back-EMF harmonic content.…”

“…The star of slots of the back-EMF harmonic of rank (2n + 1) with n = 0 of the FSPMSMs identified in paragraph II-A1 (case 1) of Part 1 [11], are shown in Fig. 1.…”

“…A comprehensive survey dedicated to a systematic identification and topological characterisation of all FSPMSMs equipped with phases made up of single coil parallel branches, has been proposed in [11]. The targeted topologies exhibit the highest open-circuit fault-tolerance potential on one hand and require the lowest DC-bus voltage on the other hand.…”

“…The present paper takes back the candidates identified in [11], in order to investigate the possible circulating harmonic currents in the loops created by the parallel branches. These would be harmful for the features of the targeted topologies.…”