Electromagnetic Transient Analysis Of Linear Induction Motors Excited By PWM Voltage With Secondary Discontinuity

The urban rail train driven by linear induction motor has the advantages of small vehicle structure,light weight,flexible marshalling,good traction performance,small turning radius and strong climbing ability.It meets the needs of urban development and has been widely used at home and abroad.However,the secondary plates of the linear induction traction motor can't be laid continuously in the road bends,turnouts and the sections where vehicles enter and leave the stations.When vehicles pass through the missing areas,the electromagnetic force will decrease and the current will increase,resulting in thrust impact and frequent over-current,which will affect the safety of train operation.In this thesis,the performance of motor with secondary missing is studied.First,this thesis reviews the development of linear induction traction motor,introduces the traffic lines of linear induction traction motor at home and abroad,and summarizes the advantages and disadvantages of linear induction motor in practical application.Combining with the research direction,this thesis introduces the research status of secondary discontinuity and the necessity of using PWM voltage supply mode,and clarifies the significance and purpose of this study.Then,this thesis analyses the structure,force characteristics and the edge effect of linear induction motor,and combines these characteristics of linear induction motor,analyses the possible electromagnetic performance changes of linear induction motor and reasons under PWM voltage supply.Second,this thesis introduces the parameter requirements and design process of the linear induction motor model,establishes the model of the linear induction motor with complete secondary and the model under five kinds of secondary missing degree,including one pole missing,two pole missing,200 mm missing,300 mm missing and complete missing.Then,in view of the above five secondary missing degrees,this thesis first uses standard sinusoidal voltage power supply to simulate the linear induction motor,and then analyses the changing rules of thrust,normal force,self-inductance and mutual inductance,and makes clear the changing trend of each parameter of linear induction motor under different missing degrees.Third,in order to be closer to the actual operating conditions,this thesis uses the PWM voltage as the excitation source,then builds the PWM inverter circuit in the Simplorer software,and performs harmonic analysis on the output voltage to establish the optimal control parameters.Then,the PWM inverter circuit module in Simplorer and the motor module in Maxwell software are used to perform field-circuit coupling finite element simulation to analyze the performance of linear induction motor under non-standard sinusoidal voltage supply,including electromagnetic force,current and various losses.Finally,the simulation results are compared to clarify the similarities and differences of the electromagnetic performance changes of linear induction motor under the above two different power supply modes,and the additional influence of PWM voltage supply on the special condition of secondary discontinuity.