Fault-Tolerant High-Power Two-Phase Coreless AFPM Motor-Drive System Concept

This paper proposes a fault-tolerant, high-power two-phase coreless axial flux permanent magnet (AFPM) motordrive system concept. Initially, the performance of a two-phase variant of the coreless AFPM machine is compared with that of its three-phase counterpart using both 3D finite element analysis (FEA) and experiments. Thanks to the intrinsic unique features of coreless AFPM machines, the analysis of the results demonstrates that the two-phase configuration has comparable power density (kW/kg) and efficiency. In terms of fault tolerance, the two-phase configuration exhibits superior performance, as the mutual inductance between phases is zero, resulting in an electric machine with magnetically decoupled phases. Hence, the adverse effects of stator winding faults in one phase do not propagate to another. The proposed two-phase motor-drive system concept was demonstrated with a coreless AFPM machine featuring a modular printed circuit board (PCB) stator. The normal and post-fault operation of this machine was experimentally evaluated with a two-phase SiC-based control system with a high switching frequency to reduce current ripple due to the ultra-low phase inductance in coreless machines. Results demonstrated that, thanks to the magnetically and electrically isolated phases of the proposed motor-drive system, the machine can still operate after isolating the faulty phase using the controller.