Improvement of Electromagnetic-Thermal Characteristics in a Modular In-Wheel Motor Under Open-Circuit Faults and Asymmetric Working Winding Operations Based on Fault-Tolerant Strategy

Multi-unit modular in-wheel motors have a high utilization rate of remaining healthy windings and a high-power density during fault-tolerant (FT) operations. However, when the open-circuit faulty motor operates with FT control, the working windings are asymmetric in the circumferential space, which will cause some problems, such as decreased electromagnetic characteristics and local windings with a higher temperature. This paper aims to mitigate the disadvantages caused by asymmetrical working winding operations, and to explore the FT strategies to comprehensively improve the electromagnetic-thermal characteristics under FT operations. First, the main types of opencircuit faults for the modular motor are introduced, and the impact mechanisms of asymmetric winding operations on MMF, torque performance are analyzed respectively. Thereafter, the FT strategies based on MMF compensation and torque performance improvement are obtained respectively. Secondly, the influence of FT strategies on the efficiency, the loss and temperature distributions of the motor under asymmetric winding operation is investigated. And the above FT strategy is upgraded, which not only enhance electromagnetic characteristics but also improve the thermal characteristics of the remaining healthy windings. Finally, the improvement effect of the FT strategies on the electromagnetic-thermal characteristics FT control and asymmetric working winding operations are verified by experiments.