Research On Fault-Tolerant Permanent Magnet Synchronous Machine For Electric Vehicles

To electric vehicles and other facilities who desire high reliability for the electric drive system, traditional three-phase machine could not meet the requirement. While multi-phase motor has the advantage of high power density and low torque ripple, also multi-phase motor could cover the rigorous requirement of electric vehicles for high reliability. This thesis is about multi-phase fault-tolerant motor , the motor can not only work as high performance electric drive system solutions for next generation of electric vehicles, but also can be popularized to ship propulsion, aerospace and other fields.First, characteristic of fault-tolerant motor was analyzed, and basic principle of fault-tolerant motor design was confirmed. Phase number was determined based on the balance of many factors, then basic electric and magnetic relations of the motor was deduced, considering all above conclusions the design method based magnetic circuit was proposed, then finite element method was used to verify correctness of the proposed method.Second, inductance parameter calculation method based on finite element analysis results was studied, the effect on inductance parameters due to cross magnetization was considered, and appreciate technical process about the inductance parameters calculation was proposed. Effect of inductance parameters due to cross magnetization was analyzed.Next, multi-phase motor has specific requirement of high power density and low torque ripple, so appropriate winding arrangement was chosen, after that, effect to the motor electric performance about the change of pole arc factor, magnetization direction and slit width was studied, optimal design of the motor was determined, and electric performance of the motor in full speed range was analyzed based on the optimal design model. Then, The electric torque performance was analyzed with the fault about one-phase open, two-phase open, and one-phase short-circuit, respectively. The origin of torque ripple in fault conditions was discussed using phasor method.At last, harmonic distribution of magnetomotive force (MMF) in air gap was analyzed, eddy-current loss in permanent magnets (PMs) due to subharmonic was studied, and effective method to decrease the eddy current loss in PMs was proposed.