The Levitation Drift Characteristic Of High Temperature Superconducting Maglev

Since the discovery of the high temperature superconducting(HTS),its wide application prospects has quickly attracted people’s attention.From advanced information technology to medical science,from power application to energy conservation,from basic science to transportation,various superconducting devices have their respective advantages.Especially,HTS bulks have won the favor of researchers,and are widely used in magnetic levitation bearing,flywheel energy storage system,HTS maglev vehicle.Especially,the research of HTS maglev vehicle has experienced nearly 30 years’ development,and has made great progress.In the early study of HTS maglev vehicle,most studies were conducted on the quasistatic situation,including the levitation force and guidance force,damping hysteresis relaxation.The dynamic behavior and evolution of levitation performance were studied little.Because of the producing mechanism of HTS levitation and guidance force,it derived from the lattice defects of HTS bulks,and it is inevitable in the process of movement which will produce magnetic flux creep and flux flow,re-magnetization phenomenon again.In the early study,the change of the load,the external magnetic field and time will influence the levitation position of HTS bulks.This phenomenon is called levitation drift(LD),which will influence the stability of HTS maglev vehicle.The experiment of this paper is conducted on the 45-m ring test line in the State Key Laboratory of Traction Power Southwest Jiaotong University.The main research contents and conclusions are as follow:(a)The HTS malgev vehicle LD behaviors at different field cooling heights with long time will be conducted.Conclusion: With the increase of running time,the frequency of the levitation system will increase slightly,and the LD will gradually stabilize.The power function can be used to better fit the variation of the LH.The exponential function can be used to better fit the variation of the LD with time.Through fitting curve calculation,we can conclude that the HTS maglev vehicle has the characteristics of maintaining long-term stability.(b)By studying the effects of speed,offset load and cyclic load on the suspension drift of HTS maglev vehicle.Conclusion: The increase of velocity will result in the increase of horizontal and vertical levitation drift;The offset load will increase both the vertical levitation drift of the cryostat at the offset load and the lateral levitation drift;Cyclic load will increases vertical levitation drift.So in practical application,offset load should be avoided.(c)Preloading,copper eddy current damper and field cooling eccentricity are used to improve the LD of the vehicle.Conclusion: The preloading can restrain the lateral and vertical LD of the vehicle;The effect of copper eddy current damper is not obvious under low-speed motion;Field cooling eccentricity can restrain lateral LD.Based on the improvement of field cooling eccentricity,the author proposes a staggered steering mechanism for HTS maglev vehicle.(d)Based on the Adams software,according to the actual parameters of HTS maglev vehicle on the ring test line,its moving on the ring test line is simulated.By comparing the simulation results with the actual test data,the vertical vibration transmission can be reduced by adding a vertical damper.(e)A new type of bogie structure with independent suspension unit is proposed.The trajectory of the new maglev is compared with that of the original maglev.The results show that the maximum LD of No.1 and No.2 cryostat of the new maglev vehicle is smaller than that of the original maglev vehicle in the straight line section.In the curve section,the maximum LD of the No.1 cryostsa in the new maglev vehicle is smaller,and the maximum LD of No.2 cryostsa is basically the same as that of the original maglev.The results show that the new independent suspension unit bogie structure can reduce the LD of cryostsa better,thus reducing the generation of LD.In this paper,the LD characteristics of HTS maglev vehicle under long-term and multiworking conditions are studied,and various improvement methods are put forward,which have certain reference value for the design and application of HTS maglev vehicle.