Research On A Five-phase Fault-tolerant Permanent Magnet Synchronous Machine Used For Electric Vehicle

Compared to three-phase machine system, the multi-phase machine systemhas better fault tolerance performance, which greatly improves the security andreliability of the electric vehicle motive power system. Therefore, multi-phasemachine system provides a new solution for electric vehicle power actuator, andpromotes the development of the electric vehicle market. In this paper, machinedesign, performance analysis, optimum torque control under fault conditions,three-dimensional temperature field and other aspects for a five-phasefault-tolerant permanent magnet synchronous machine used for electric vehicleare analyzed and studied.Firstly, combined with the design requirements for multi-phase fault-tolerantmachine, the winding arrangement form, selection of pole and slot combination,armature magnetomotive force harmonic analysis, and coil inductance is studied.A42-slot/42-pole machine and a20-slot/18-pole one are confirmed, and the twodesign schemes are compared.Secondly, aming at the requirements of machine fault-tolerant performance,electromotive force (EMF) should be sinusoidal. Two common methods ofeccentric permanent magnet structure and halbach magnet array are adopted tooptimize EMF. Direct axis and quadrature axis inductances are obtained by EMFmethod considering the influence of magnetic circuit saturation Additionally, theimpacts of stator slot size on short-circuit current is analyzed.Thirdly, the permanent magnet eddy current loss is big due to theconcentrated winding form. Therefore, the reasons and influencing factors ofeddy current losses are analyzed, and then reduce eddy current losses bypermanent magnet segmentation. In addition, the efficiency characteristics of themachine is calculated, meanwhile, efficiency MAP is drawn so as to determinethe efficiency characteristics at different operating point in the operating region.Fourthly, considering that the torque ripple is large under fault conditions,an optimal torque control strategy for reducing torque ripple is proposed. Thetorque output performance when working with fault-tolerant control strategy isverified by Flux-Simulink joint simulation, and compared to the torque outputperformance without fault-tolerant control strategy.Finally, heat source of the machine is analyzed, and stator water coolingsystem is designed. At the same time, temperature distribution of variouscomponents of the proposed machine is calculated through the simulation of three-dimensional temperature field.