Study On The Dynamic Characteristics And Improvement Methods Of High Temperature Superconducting Maglev

Superconducting phenomenon was found since 1911,because of the zero resistance,Meissner effect,Josephson effect and flux pinning effect,superconducting has been applied to superconducting generators,superconducting cables,superconducting magnetic levitation?Maglev?,thermonuclear fusion reactor,superconducting electromagnetic cannon,superconducting computers and many other aspects.In 2000 the superconducting team led by Wang Jia su researcher of the Southwest Jiaotong University developed successfully the world's first manned high temperature superconducting?HTS?maglev test vehicle,then many countries in the world have carried out the research of HTS maglev.Early days the research about HTS maglev was mainly focused on quasi-static,including static levitation force,guiding force,magnetism,rigidity and so on.In the future,engineering application of HTS maglev must be carried out in a dynamic environment.So we must carry out its research about dynamic characteristics.However,in the actual operation,the HTS maglev will inevitably experience the non-uniform magnetic field environment,which will inevitably affect its suspension characteristics.In this paper,the dynamic characteristics of superconducting bulks under non-uniform magnetic field are studied by HTS maglev dynamic test system.The paper mainly studied the dynamic levitation force and magnetic field change signals of different locations at upper and lower central surface of YBCO and GdBCO bulks under different external magnetic field environment.From the view of magnetic signal we analyze the reasons of the change of levitation force,and then comprehensively compare the suspension performance of two different bulks,which will provide meaningful reference for future engineering HTS maglev bulk selection.Then the paper studied the evaporative properties of liquid nitrogen?LN₂?at different operation speeds and different field cooling heights.Alternating current?AC?loss characteristics of HTS bulks were deduced from the evaporation characteristics of LN₂ under the change of external magnetic field.Then we calculate the temperature rise and AC loss characteristics of HTS bulks under different external magnetic fields by using the COMSOL software.Finally,according to the experimental and simulation results,two methods are proposed to improve the magnetic levitation characteristics of HTS superconductors:one is to replace YBCO bulk materials with GdBCO bulk materials;the other is to reduce the frequency and amplitude of external magnetic field changes during dynamic operation and try to keep the external magnetic field constant.