Experimental And Simulation Study On Magnetic Levitation Characteristics Of High-temperature Bulk Superconductor Above Electromagnetic Guideway

Flux exclusion and magnetic flux pinning of high-temperature superconductor(HTSC)enable it to stably levitate or suspend above or below magnet,showing its unique levitation characteristics.The technology of using permanent magnets(PMs)as high-temperature superconducting(HTS)magnetic levitation(Maglev)guideway has been fully verified.Electromagnetic guideway(EMG)has the advantages of adjustable levitation characteristics,instant excitation and relatively simple routine maintenance.It has potential technical and cost advantages in long-distance HTS Maglev rail transit system.So far,in HTS Maglev rail transit system,there is still a lack of systematic research on the levitation characteristics of HTSC above EMG at home and abroad.Based on these considerations,this thesis proposes to use EMG to replace PMG in HTS Maglev rail transit system,and studies characteristics of HTS bulk(s)above the EMG through experiments and simulations.The main contents are as follows:(1)The levitation characteristics of bulk HTSC under the magnetic fields generated by different structural parameters of electromagnetic guideway units(EMGUs)are studied,including levitation force under current regulation mode and vertical motion mode,and guidance force under lateral motion.(2)A segregated three-dimensional model,consisting of a static EMGU(s)model and a time-varying superconductor model,for studying the levitation characteristics of HTSC moving above the EMG with adjustable current is proposed and establised.The experiments and simulations were carried out on the levitation force of a bulk HTSC in the magnetization process and the influence of the current adjustment on levitation stability of a sample above an EMGU.The mechanism that causes these levitation characteristics are discussed by the simulation results of the electromagnetic relationship inside the superconductor.(3)In order to improve the magnetic field provided to the superconductor,the EMGU is optimized according to the optimization principle.The dynamic levitation characteristics of a single HTS bulk and multiple samples above the EMGU(s)are studied through experiments and simulations.The mechanism that causes these levitation characteristics are analyzed through simulation results.(4)The method of segmented excitation(SE)adjustment in simulation is realized and its rationality is explained.On this basis,the dynamic levitation characteristics of a bulk HTSC under the mode are studied,proposing coordinated control strategy(CCS)between EMGUs.The EMG can provide a longitudinal uniform magnetic field for smooth operation of HTSC.By adjusting EMG current,levitation performance of HTSC above EMG can be adjusted or improved.When multiple bulks levitate above the EMG,the position of the bulks in magnetic field environment and the relative position between bulks should be considered to prevent damage and fracture of bulks due to severe uneven force,which will affect the levitation performance and safe operation of the whole vehicle.The CCS between EMGUs can maintain the levitation force when the superconductor travels straight along the EMG under the SE mode,and proves the feasibility of the SE mode.The simulation results obtained by the model reflect the experimental results well qualitatively and quantitatively,which illustrates the validity of the model that can be used to analyze the mechanism of the levitation characteristics of HTSC above the EMG.These results will provide an important reference and basis for the practical application and further study of the EMG used in HTS Maglev rail transit system.