| Due to magnetic field modulation effect,permanent magnet vernier machine can obtain high torque density.Its characteristics of low speed and high torque make it have great potential to be used in various electric propulsion systems.Meanwhile,in the electric vehicle,ship propulsion,aerospace and other occasions where high reliability is required,in addition to the torque performance is highly demand,but also the high fault-tolerant performance is required.Therefore,the permanent magnet fault-tolerant vernier(FT-PMV)machine that meets both of these performance requirements has gradually attracted attention.However,the previous research on this kind of machine is limited to the new structure.The systematic theoretical analysis of the machine performance is lacked.As a result,the research on the performance improvement of this kind of machine is lack of theoretical guidance.In this thesis,the analytical expressions of air-gap flux density,no-load back-EMF,output torque,self-inductance,mutual inductance,short-circuit current and power factor of this kind of FT-PMV machine are derived by establishing the analytical models of air-gap permeance,permanent magnet magnetomotive force(PM MMF)and equivalent magnetic circuit(EMC).Based on the derived analytical expression,the influence mechanism of design parameters of FT-PMV machine on torque performance,fault-tolerant performance and power factor is studied,and the design scheme of FT-PMV machine with improved torque performance,fault-tolerant performance and power factor is proposed respectively.Specific research will be carried out from the following aspects: 1.Through the theoretical analysis of the torque performance of the FT-PMV machine,the influence mechanism of the design parameters on the torque performance is studied,so as to guide the design of the machine with high torque density.Firstly,the influence mechanism of the design parameters on the torque performance was studied by establishing the mathematical analytical models of the air-gap permeance and PM MMF of the machine.Secondly,FT-PMV machines with appropriate ratio of pole slots are selected for modeling and simulation to verify the correctness of the theoretical analysis of output torque. Finally,the design criterion of high torque density of FT-PMV machine is presented.2.Through the theoretical analysis of fault-tolerant performance and power factor of the machine,the influence mechanism of the design parameters on the power factor and fault-tolerant performance is studied,so as to guide the design of the machine with high fault-tolerant performance and high power factor.Firstly,the EMC model of the machine is established,and the influence mechanism of design parameters on self-inductance,mutual inductance,short-circuit current and power factor is studied.Secondly,the finite element simulation models are established to verify the correctness of the theoretical analysis.Finally,the design criterion of high fault-tolerant performance and high power factor of FT-PMV machine is presented.3.Through the comprehensive theoretical analysis of the output torque,fault-tolerant performance and power factor,the design criteria of FT-PMV machine that comprehensively improves the output torque and fault tolerance performance and comprehensively improves the output torque and power factor are studied in this thesis.First of all,the influence mechanism of design parameters on the output torque,mutual inductance,short circuit current and power factor is analyzed.The design criteria of FT-PMV with improved output torque and fault-tolerant performance as well as improved output torque and power factor are put forward under the condition of integrating these influence mechanisms and making necessary trade-offs.Secondly,the above analysis results are verified by finite element simulation on the models.4.Experiments are carried out on prototype to verify the correctness of theoretical analysis and simulation analysis of FT-PMV machine.Firstly,the prototype is tested without load to verify the correctness of the theoretical analysis of the no-load back-EMF and the coupling between phases.Secondly,the load test of the machine is carried out to verify the correctness of the analysis of the output torque,short circuit fault-tolerant performance and short circuit current. |
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