Research On Orbital Eddy Current Brake With The Ring Winding Structure And AC Excitation

Eddy Current Brake(hereinafter referred to as "ECB")is an electromagnetic brake device based on Faraday’s electromagnetic induction law and eddy current principle.It is commonly used in eddy current braking systems of high-speed trains.Compared with traditional mechanical braking methods,the braking force is not limited by the friction coefficient between the wheel and rail,and the reliability is high and the maintenance is convenient.In this paper,an orbital eddy current brake with the ring winding structure and AC excitation is proposed.The mathematical model is derived by analytical method.Based on the mathematical model,the design method of ECB with AC excitation is proposed.The structural parameters are optimized and the braking characteristics are analyzed.Firstly,the basic structure of orbital ECB system with the ring winding structure and AC excitation is proposed,and its working principle is elaborated.Subsequently,a layered model of orbital ECB with AC excitation is established.The current-carrying primary winding is equivalent to the traveling wave current layer,and the influence of the primary slot is compensated by the air gap coefficient.At the same time,starting from Maxwell’s equations,the vector magnetic potential equations in each region are derived.Combined with the boundary conditions,the expressions of ECB eddy current loss,braking force and normal force are obtained,that is,a complete two-dimensional mathematical model of orbital ECB with the ring winding structure and AC excitation is established.Next,a two-dimensional finite element model of ECB is established to verify the accuracy of the two-dimensional mathematical model.Secondly,in order to improve the accuracy of the two-dimensional mathematical model,one-dimensional field theory,Schwarz-Christoffel transform and other methods are used to adress the four end effects of ECB,and a complete three-dimensional mathematical model of orbital ECB with the ring winding structure and AC excitation is established.Next,a three-dimensional finite element model of ECB is established to verify the accuracy of the three-dimensional mathematical model.Thirdly,according to the technical requirements of ECB and the actual installation environment,the design flow and design method of orbital ECB with AC excitation are proposed.Combined with the derived mathematical model and finite element analysis results,the design parameters of ECB are optimized.Combined with the derived mathematical model and finite element analysis results,the structural parameters of ECB are optimized,and the main dimensions,pole-log and pole pitch,cogging size,primary core yoke height and primary winding parameters are gradually determined.In addition,the braking characteristics of ECB with different winding forms are compared to verify the advantages of the ring winding structure.Finally,the finite element model is used to obtain the braking characteristics under different excitation conditions,secondary conductivity,air gap length and the coupling area of primary and secondary,revealing the variation law of the braking force,normal force and rail cooling rate with primary current density,primary current frequency and slip rate.According to the constant flux regulation method of traditional induction motor,the constant flux braking method suitable for AC excitation orbital ECB with the ring winding structure is proposed,and all the characteristics of ECB are completed.