Influence of Thermal Conductivity on Guidance Force Decay of HTS Bulk Exposed to AC Magnetic Field Perturbation in a Maglev Vehicle System

Bulk superconductors have great potential for various engineering applications, especially in a high-temperature superconducting (HTS) maglev vehicle system. In the vehicle system, the stable levitation can be achieved without any complex control system owed to the pinning effect of the bulks. However, the HTS bulks in the vehicle system were always exposed to the time-varying external magnetic field, which was generated by the inhomogeneous surface magnetic field of the NdFeB guideway. In our previous work, we studied the guidance force decay characteristics of the YBCO bulk over the NdFdB guideway used in the HTS maglev vehicle system by an experiment in which the AC external magnetic field generated by an electromagnet was used to simulate the time-varying external magnetic field caused by the inhomogeneity of the guideway, and calculated the guidance force decay as a function of time based on an analytic model. In this paper, we investigated the influence of thermal conductivity on the guidance force decay of HTS bulk exposed to AC field perturbation in the maglev vehicle system and tried to adopt a method to suppress the decay. From the results, it was found that the guidance force decay rate was higher for the bulk with the lower thermal conductivity. So, we could reduce the guidance force decay of the HTS bulk exposed to the AC external magnetic field perturbation in the maglev vehicle system by improving the thermal conductance of the bulks.