Research On Multiphase Fault-tolerant Permanent Magnet Synchronous Motor Used In Electric Vehicle

With the development of science and technology,the problems of energy and environment become more and more serious.The problem of automobile exhaust pollution is focused by more people,therefore the problem can be alleviated by the emergency of electric vehicles.The electric vehicles feature low pollution,low noise,saving energy and many other advantages,thus the electric vehicles are highly concerned in recent years.Its drive motor,as the core of electric vehicles,is required with high torque,low torque ripple and high reliability.However,compared to the traditional three-phase permanent magnet synchronous motor(PMSM),multi-phase PMSM performs better on the above characteristics.Therefore,six-phase fault-tolerant PMSM for electric vehicle is designed and analyzed in this thesis.Firstly,the classification,structure and design principle of multi-phase PMSM are introduced in this thesis.According to the winding structure of multi-phase motor,the definition of the phase number in multi-phase motor is illustrated,and the relationship between the stator winding and phase spread of multi-phase motor is summarized subsequently.Meanwhile,different types of winding and their characteristics are presented in this thesis.Moreover,the structure and advantages of six-phase double Y shift 30° winding are introduced.According to the theory of winding magnetomotive force,the magnetomotive force of six-phase double Y shift 30° winding is analyzed and the relationship between magnetomotive force and electromagnetic torque is analyzed correspondingly.Secondly,according to the design method of traditional three-phase PMSM,the electromagnetic design of the six-phase double Y shift 30° winding PMSM is proposed based on the theory and characteristics of multi-phase winding.Then,the electromagnetic load,the slot-pole combination,the structure of rotor,and the material and size of permanent magnet are analyzed.By employing the software Ansoft,a six-phase PMSM with double Y shift 30° winding simulation model is constructed.As a result of that,the air gap flux density,back electromotive force and cogging torque of the proposed PMSM under no-load is simulated and analyzed respectively,and the air gap flux density,output torque and core loss on load are simulated simultaneously.All the simulation results are compared with the traditional three-phase PMSM.In order to increase torque performance further,the third harmonic current is injected into the six-phase double Y shift 30° winding PMSM.Finally,the performance of open-phase fault is studied as follows.On one hand,by software Ansoft,torque performance of six-phase PMSM with double Y shift 30° winding under three situations are calculated,which is one phase open,two phases open and three phases open.On the other hand,by analyzing the negative sequence component of magnetomotive force,focus on torque ripple of six-phase double Y shift 30° winding PMSM with one phase open,one method which can minimize torque ripple by adjusting the phase angle of the other phases is studied and analyzed.The software Ansoft is employed to prove the feasibility and validity of the proposed method.