| The operation of the high-temperature superconducting(HTS)magnetic levitation train requires the interaction of the external magnetic field with the high-temperature superconductor and the use of magnetic flux pinning characteristics to provide levitation and guidance;therefore,changes in the external magnetic field will affect the levitation,guidance,and generation in the direction of motion influences.At the same time,changes in the external magnetic field will also cause AC loss and internal temperature rise in the high-temperature superconductor.Excessive temperature rise will affect the stability of the high-temperature superconductor.Therefore,studying the influence of external magnetic field changes on the electrical,magnetic and thermal properties of high-temperature superconductors is of great significance to the operational stability of maglev trains.At present,the research related to the dynamic characteristics of HTS magnetic levitation mainly focuses on the influence of external magnetic field on the levitation force and guiding force,while the influence of external magnetic field on the running direction is rarely paid attention to.In this paper,in order to study the external magnetic field changes,the following research work is mainly carried out on the force of the high-temperature superconducting bulk in the direction of motion:Firstly,in order to study the influence of changing external magnetic field on the direction of the superconducting maglev,different layers of silicon steel sheets are laid to achieve different degrees of magnetic field fluctuations to achieve the magnetic field inhomogeneity of the annular permanent magnet track.In the dynamic running experiment of the sidesuspension maglev prototype vehicle,the influence of the running speed and the degree of magnetic field fluctuation on the running direction is explored.Secondly,a three-dimensional model was established using commercial finite element analysis software to calculate the movement process of the high-temperature superconducting bulk under external magnetic field fluctuations,so as to further explore the reasons for the magnetic resistance.Finally,through the multi-physics coupling function of the finite element software,the magnetic field and the thermal field are coupled and calculated to obtain the superconducting bulk in a fluctuating external magnetic field environment.The AC loss and temperature distribution inside the superconductor will explore whether the temperature rise will affect the stability of the superconductor and the magnetic resistance.The main conclusions from the above research are as follows:(1)The magnetic resistance of the side-suspension HTS maglev prototype vehicle increases with the intensity of the magnetic field fluctuation and the increase of the moving speed;(2)In the magnetic resistance simulation,the suspension height is set unchanged,the high-temperature superconducting bulk will experience the magnetic resistance and the restoring force successively when entering and leaving the magnetic field fluctuation area.The average resistance experienced during the whole process is very small.The change of the average resistance of the process still increases with the increase of speed;(3)In the AC loss simulation,the HTS bulk increases with the fluctuation of the external magnetic field at the same speed,which causes its internal AC loss to increase and the temperature rise is more obvious;When the HTS bulk moves at different speeds under the same external magnetic field environment,the instantaneous AC power loss and temperature rise inside it increase with the increase of the moving speed.The AC loss per unit time,the speed of movement and the degree of magnetic field fluctuations all increase with the increase.The temperature rise area of the high-temperature superconducting bulk material mainly appears in the area where the induced current is the largest.The temperature rise in this simulation has a limited effect on the stability of the high-temperature superconducting bulk. |
