A Fault Tolerant Electric Propulsion Unit Based on Bifilar Coils

This paper presents a novel fault tolerant electric propulsion unit concept based on a permanent magnet motor with concentrated tooth-coil winding. A stator winding of an electrical machine is wound using bifilar coils, and each bifilar coil is supplied by separate inverter modules while ensuring the same current direction in the slots and, thus, an additive current linkage. The proposed design aims to prevent the possibility of inter-turn short circuit faults within the same coil. Such faults can cause the most severe local fault currents in a stator winding in case of a single-turn short circuit. The paper investigates the effect of turn-to-turn short circuits between bifilar coils and possible detection mechanisms using finite element analysis. The evaluation of differential current and zero sequence current is utilized to detect turn-to-turn faults at an early stage and are shown to provide sensitive detection capabilities.