Distribution Characteristics Of The Applied Magnetic Field Above PMG In HTS Maglev System

When the high-T_csuperconductor（HTS）bulk working in the liquid nitrogen temperature is placed in a specific external magnetic field,it has stable suspension and guidance due to its own superconducting inductivity and flux-line pinning characteristics.Maglev train based on this self-stability system has attracted more and more attention in the field of ground transportation in the future.In the HTS maglev train system,the applied magnetic field provided by permanent magnet guideway（PMG）has played a key role in maintaining the stable operation of the maglev vehicle.In practice,PMG is faced with complex defects due to influence of magnet processing technology and assembly accuracy,which may lead to inhomogeneity distribution of magnetic field along the longitudinal direction and asymmetric distribution of the magnetic field along the transverse direction above PMG.The characteristic makes the maglev vehicle under magnetic drag,causing AC loss,thus affecting the running stability of the HTS maglev vehicle.Based on this,this paper systematically studies the distribution characteristics of the applied magnetic field above the PMG through experimental testing and simulation calculation,and the research results provide design reference for the development and construction of higher performance PMG technology.In order to explore and reveal the longitudinal and transverse distribution characteristics of magnetic field above the PMG and their causes,as well as their effects on the static levitation force of YBa₂Cu₃O_7-x（YBCO）.The finite element simulation models of the HTS Maglev system and the PMG segment is built by COMSOL Multiphysics software to calculate the distribution of magnetic field above the PMG and the static levitation force of the YBCO bulk.The tri-axial motion experiment platform was further designed and built.The surface magnetic field above the PMG,the upper surface profile of the PMG and the static levitation force of the YBCO bulk were measured successively by the corresponding testing equipment.The simulation and experimental results show that there are many defects in the actual PMG,resulting in the uneven longitudinal distribution and asymmetric transverse distribution of the magnetic field above the PMG,and the difference in the static levitation force of YBCO bulk at different longitudinal and transverse symmetric positions of the PMG.The accuracy of the finite element method in analyzing the magnetic field above the PMG is verified by comparing the experimental results with the simulated results.In order to solve the problem that the curved PMG is difficult to assemble and cost stays relatively high.This paper firstly studies the magnetic field distribution characteristics above it through finite element simulation.Firstly,a Halbach-type mechanical structure of the curved PMG is presented,and the mathematical expressions of the parameters of each structure are derived successfully.According to the optimization results of the formula,a small-scale curved PMG model is established,which is preliminarily verified by simulation calculation.Secondly,the influence of configuration defects on the distribution of magnetic field above the curved PMG is studied.Finally,the magnetic field distribution above the PMG in the straight line state and the track change state is studied.