Analysis Of Three-dimensional Magnetic Force Characteristics Between Metallic Vacuum Tube And Superconducting Electrodynamic Suspension System

With the development of high-speed railways,passengers’travel has become more convenient,and their travel time has been greatly shortened.However,affected by the adhesion limit and the aerodynamic resistance,the maximum operating speed of traditional wheel-rail trains is limited to about 350 km/h.In 2015,the Japanese low temperature superconducting electrodynamic suspension(EDS)train achieved a speed of 603 km/h for manned operation,which proved the feasibility of the superconducting EDS system for high-speed operation.In addition,the combination of low vacuum tube and superconducting EDS system can further reduce the restriction of aerodynamic drag,and is expected to achieve high-speed and ultra-high-speed operation goals.Therefore,this article focuses on the superconducting EDS system and the vacuum tube as the main object and studies the levitation and guidance performance of the superconducting EDS and the magnetic force characteristics after adding the metallic vacuum tube.It is expected to provide some reference to the metallic-vacuum-tube(MVT)-superconducting-EDS applications.First,this paper establishes a three-dimensional finite element analysis model of a superconducting EDS system,and theoretically derives the calculation expressions of the dynamic circuit analytical method.Under the same operating conditions,the finite element method(FEM),the analytical method and the experimental data results by Japan were compared,and then the FEM model was revised.Based on the FEM and the analytical method,the variation trends of levitation force,guidance force and drag force in the speed range of 0～500 km/h are compared,and the dynamic operating characteristics at the constant speed of500 km/h are analyzed.The results show that the FEM data and the analytical method are in good agreement,which verifies the reliability of the FEM.A single superconducting magnet and two opposite-pole magnetic superconducting magnets are used to analyze the force characteristics of the superconducting magnets under different operating conditions.The results show that at the speed of 1000 km/h,a single superconducting magnet can be substituted for two opposite-pole magnetic superconducting magnets for FEM.Secondly,considering the air-tightness and economy of the materials,the suitable material types of vacuum tube for superconducting electrodynamic levitation systems are compared,and the suitable metallic vacuum tube model for superconducting EDS systems is preliminarily established.For the relative permeability,bulk conductivity,radius and thickness of the metallic vacuum tube,the guidance force and drag force of the induced magnetic field in the metallic vacuum tube are studied when the superconducting magnet runs at a speed of1000 km/h.The recommended parameters of the metallic vacuum tube are obtained.For example,relative permeability is 1,bulk conductivity is 1.1×10~6 S/m,radius is 3.5 m.When the thickness is greater than 40 mm,the pressure resistance and air tightness of the vacuum pipeline must be met.At the same time,it is analyzed that at this operating speed,the magnetic field in the null-flux coil has almost no effect on the magnetic force characteristics of the metallic vacuum tube.Finally,for the variety of operating modes,the magnetic force characteristics between the superconducting magnet,the null-flux coils and the metallic vacuum tube are analyzed.The main conditions include:the superconducting magnet operating speed range of 0～1000km/h,the channel width between the metallic vacuum tubes,and the installation height of the null-flux coils in the vacuum tube.The results show that the null-flux coil has little effect on the metallic vacuum tube.In conclusion,this paper takes metallic vacuum tube and superconducting EDS systems as the research objects.Based on the established three-dimensional FEM model,the magnetic force characteristics among superconducting magnets,null-flux coils and metallic vacuum tube are analyzed.The relevant conclusions provide a theoretical reference for engineering applications to some extent.