Design Of Ladder Type Secondary And Research On Performance Improvement Of Linear Induction Traction Motor

The linear induction motor can directly generate linear motion without the need of a transmission mechanism,which makes the mechanical structure simple,low noise,and is not affected by the adhesion coefficient.In the field of rail transit,it has many outstanding advantages such as small turning radius,strong traction ability and strong climbing ability,so linear induction motor has been successfully used in urban rail transit.However,linear motors also have problems such as low efficiency and power factor.Therefore,this thesis is mainly to improve the efficiency of linear induction motor and improve the performance of the motor.Due to the ladder-type secondary structure can regulate the path of the secondary induced eddy current and weaken the transverse end effect,the body design and electromagnetic characteristics analysis of linear induction motor with the ladder-type secondary are studied in detail in thesis.Firstly,the principle and structure of ladder type linear motor are introduced.The electromagnetic force and eddy current distribution of ladder type linear motor are analyzed.The advantages and disadvantages of ladder type secondary are summarized.Secondly,by referring to the theory of rotating electric machine,two sets of typical slot conbinations between primary and secondary are selected The finite element calculation of the ladder type linear induction motor with two slots conbinations is carried out,and the influence of different slot conbinations between primary and secondary on the ladder type linear induction motor is analyzed.The electromagnetic characteristics of the linear motor with different slot conbinations are obtained,such as:electromagnetic thrust,normal force and distribution of eddy current,and distribution of transverse magnetic fields,considering the engineering application,the net thrust is also calculated and the sensitivity of the two types of ladder-type secondary to different slot combination is summarized.Next is the electromagnetic design of the ladder type secondary linear motor.Firstly,the equivalent circuit of the ladder type linear induction motor and the calculation formula of the equivalent circuit parameters and related electromagnetic characteristics are introduced.Then determine the main size of the ladder type linear motor and the choice of electromagnetic load,mainly analyze the method of determining the secondary thickness and electromagnetic air gap.According to the equivalent circuit and design steps of linear motor with ladder type secondary,the script file was compiled by MATLAB to determine the air gap of the motor and the thickness of the secondary conductive plate.Finally,the influence of the variation of the width of the bar and the length of the secondary end on the electromagnetic properties of the ladder type linear motor,such as electromagnetic thrust,vertical force and net thrust,is further analyzed by the finite element method.The range of secondary bar width and end connection length are obtained.The ladder type linear motor that has been designed is modeled,and the finite element calculation is carried out in the three-dimensional field.The electromagnetic characteristics of the ladder type linear motor are analyzed and compared with the solid flat-type secondary.At the same time,the variation of thrust,normal force,secondary eddy current loss,efficiency and power factor with slip rate is calculated.It is concluded that:The ladder type secondary can improve the performance of the linear motor and improve the efficiency and power factor of the linear induction motor.