Study On The Characteristics Of Linear Induction Motor And The Improved Equivalent Circuit Considering The Overhang Length Of Secondary

Linear induction traction motor(LITM)has a good application prospect in the field of urban rail transit,among which the most used are maglev train and metro vehicle,because of it is not affected by the adhesion coefficient.However,due to its special structure,high coupling and high degree of non-linearity,LITM will produce unique effects different from the rotating motor,which makes the research on its force characteristics,electromagnetic characteristics and secondary plate width optimization more complex.In this paper,LITM used in Guangzhou Metro Line 4 is studied,including the modeling of force and electromagnetic characteristics,the improvement of equivalent circuit to achieve fast and accurate optimization of secondary width.In order to solve the problems in the analytical method of force characteristics of single side composite secondary linear induction motor used in subway,such as difficult model construction,complicated analysis,large amount of calculation and poor engineering practicability,a simplified two-dimensional four area electromagnetic model of single side composite secondary linear induction motor with simple modeling process and small amount of calculation is proposed.The equivalent circuit is composed of five parts.Considering the end effect,saturation effect and secondary skin effect,the analytical calculation formula of the relationship between secondary width and thrust and efficiency is derived according to the energy conversion relationship.Then the finite element simulation of different secondary width is carried out and compared with the results of the analysis.Finally,the experimental platform is built to verify and fully prove the equivalent circuit can realize the fast and accurate calculation of the secondary width optimization.In addition,according to the main design dimensions of the motor,the finite element simulation model of linear induction motor is built by using Maxwell 2D and 3D,and its electromagnetic transient characteristics are studied.In order to solve the problem that the thrust and efficiency cannot reach the rated design value due to the fact that the overhang length of secondary is not considered in the design process of single-side linear induction motor for metro,an improved equivalent circuit considering the overhang length of secondary is proposed.The equivalent circuit is composed of five parts.Considering the end effect,saturation effect and secondary skin effect,the analytical calculation formula of secondary width related to thrust and efficiency is derived according to the energy conversion relationship.Then the finite element simulation of different secondary width is carried out and compared with the analytical results.Finally,the experimental platform is built to verify the correctness of the analytical expression.The equivalent circuit can realize the fast and accurate calculation of thrust and efficiency.The experimental platform is built and the thrust and normal force are measured.The experimental values are compared with the theoretical values of the two-dimensional four area method and the secondary width optimization equivalent circuit,which further verifies the correctness of the two-dimensional four area electromagnetic model and the improved equivalent circuit considering the overhang length of secondary.In addition,the type test of LITM is also carried out.