An Outer Rotor Surface PM Motor With Integrated Chokes for Fault-Tolerant Operation in the Presence of Short-Circuit Faults Between Adjacent Turns

This article presents a novel design for an outer rotor surface permanent magnet (SPM) machine intended to enhance fault tolerance in the presence of short-circuit faults between adjacent turns. The proposed motor configuration uses a dual three-phase winding arrangement, wherein two distinct sets of three-phase windings have separate neutral points and are galvanically isolated from each other. The turns within each slot are interleaved to ensure that adjacent turns do not belong to the same phase or to phases that share a common neutral point. This strategic arrangement effectively transforms inter-turn short-circuit faults into phase-to-phase faults, forcing fault currents to pass through the machine's terminals. To further mitigate fault currents, the design incorporates differential mode chokes (DMCs) within the stator. For a prototype motor, a DMC inductance of 255 mu H was achieved without compromising the motor's torque. With the integrated DMC, the fault current was reduced from 25.9 to 2.65 A, and the experimental results agree well with the simulation results.