Research On Superconducting Electrodynamic Levitation And Guidance Technology Using Null-Flux Ground Coils

Superconducting electrodynamic suspension(EDS)has a wide application prospect due to the advantages of no active control,self-stability and large gap,especially in the ultra-high speed maglev,rocket launching,Electromagnetic Aircraft Launching System and other high speed fields.Superconducting coils and null-flux Ground Coils which are the primary and secondary windings respectively are applied in a typical EDS system,in that the null-flux ground coils provide levitation and guidance force.The calculation of electromagnetic forces that has been extensively studied by scholars all over the world is the basis of the design and optimization of the system.However,due to the limitation of complex structure,the calculation formula is often so complicated that the results have to be obtained by means of finite element method and numerical simulation.An analytical calculation of the electromagnetic forces for superconducting EDS system is first proposed in this paper based on the virtual displacement and the dynamic circuit approach.Different ways have been applied to experimentally validate the analytical calculation.It offers an accuracy method with high efficiency to understand the complicated system structure.The influence of each parameter on the electromagnetic force is described quantitatively,revealing the essential law between the parameters and performance of the system.The expressions of system attributes such as the stiffness and damping factor are given.This dissertation consists of following main parts:Firstly,the model of electrodynamic levitation and guidance system using null-flux coils without cross-connected structure is established.An analytical calculation of electromagnetic forces is proposed.The self and mutual inductance calculation models of multi-turn null-flux coil are established.The levitation and guidance characteristics are analyzed.This model can reveal the essential law between system parameters and performance.Secondly,the model of electrodynamic levitation and guidance system using null-flux coils with cross-connected structure is established.The levitation and guidance characteristics are analyzed,compared with null-flux coils without cross-connected structure.The results have shown that the guidance performance is significantly improved.Different ways have been applied to experimentally validate the analytical calculation.Then,the parameters of the null-flux coil are optimized,including the height,upper and lower coil clearance,cross-sectional area,number of turns,wire type and pitch.The design scheme is given,and the dynamic characteristics of the system related to the suspension height and speed are analyzed.The results have shown that the scheme can meet the needs of the system.The levitation force fluctuation is limited to5% in the range of speed exceeding 30m/s.Finally,the damping characteristics of the system are studied.An analytical calculation model of damping factor is proposed and validated by numerical simulation.The results shows that the damping factor of the superconducting electrodynamic levitation and guidance system using null-flux coils is little.The lateral and vertical damping of the system is improved from negative damping to underdamping by adding damping coils.A comprehensive and detailed analytical model of electromagnetic force and damping factor is firstly presented in this dissertation.The research results will lay a foundation for China’s ultra-high speed launch.