Armature Design of Low-Voltage FSPMSMs: An Attempt to Enhance the Open-Circuit Fault Tolerance Capabilities

Abstract

This paper deals with the torque production capabilities of fractional-slot permanent-magnet synchronous machines (FSPMSMs) under open-circuit faulty conditions. The developed approach considers a class of FSPMSMs where an armature is inserted in double-layer slots and is arranged by connecting in parallel the coils or suitable combinations of coils of each phase. In light of this, the machine operates at a low-voltage level. Accordingly, its integration within 42-V-technology-based automotive systems becomes much more realistic. Moreover, the adopted approach leads to a significant improvement in the fault tolerance capability under an open-circuit faulty operation. Indeed, a failure affecting a coil would discard one branch among the parallel branches of the corresponding phase, rather than affecting the total phase in FSPMSMs with series-connected coils in the armature. The approach is initiated by an identification allied to a characterization of the slot/pole combinations enabling the parallel connection of the FSPMSM phase coils or group of coils. Then, this paper considers the selected three-phase and five-phase FSPMSMs. Following an assessment of their healthy operation, the torque values developed by both machines are predicted using a 2-D finite-element analysis under different open-circuit faulty scenarios. Then, a simple control strategy based on the readjustment of the reference sinusoidal current initial phases is proposed to recover the torque production capability of both machines under a branch open-circuit fault.