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Bulk superconductors have great potential for various engineering applications, especially in superconducting maglev vehicle systems using high-temperature superconducting bulks. In such a system, the HTS bulks were always exposed to AC external magnetic field, which was generated by the inhomogeneous surface magnetic field of the NdFeB guideway. In our previous work, it was observed that the guidance force of the YBCO bulk over the NdFdB guideway used in the high-temperature superconducting maglev vehicle system was decayed by the application of the AC external magnetic field. In this paper, we investigate the influence of the work height on the guidance force decay of HTS bulk exposed to an AC field perturbation in the maglev vehicle system and try to adopt a method to suppress the decay. From the experimental results, it was found that the decay rate of the guidance force was smaller at higher work height in the case of the same field-cooled height. So we could suppress the guidance force decay of HTS bulk exposed to AC external magnetic field perturbation in the maglev vehicle system by increasing the work height of the bulk.

Superconducting maglev vehicle was one of the most promising applications of HTS bulks. In such a system, the HTS bulks were always exposed to AC external magnetic field, which was generated by the inhomogeneous surface magnetic field of the NdFeB guideway. In our previous work, it was observed that the guidance force of the YBCO bulk over the NdFdB guideway used in the high-temperature superconducting maglev vehicle system was decayed by the application of the AC external magnetic field. In this paper, we adopted a method to suppress the decay by altering the field–cooled height of the bulk. From the experimental results, it was found that the decay rate of the guidance force was smaller at lower field–cooled height. So we could suppress the guidance force decay of HTS bulk exposed to AC external magnetic field perturbation in the maglev vehicle system by reducing the field–cooled height of the bulk. Furthermore, all the experimental results in this paper were explained based on Bean critical-state model.

The gradeability is one of the advantages of the high-temperature superconducting (HTS) maglev vehicle, and it is relative to the levitation characteristic of the maglev system on the ramp. The influence of the ramp angle on the levitation characteristics of the HTS maglev model was investigated. Some levitation characteristic parameters on the uphill guideway with different ramp angles were studied by the equivalent experiment, such as the levitation force, the levitation gap, the levitation stiffness and the guidance force. Compared with the experimental results on the horizontal guideway, it was found that the levitation gap increased, but the levitation force and the levitation stiffness decreased. The levitation gap and the levitation stiffness are considered as the main maglev characteristic parameters needed to be taken into account.

The guidance force of the YBCO bulk over a NdFdB guideway used in the high-temperature superconducting maglev vehicle system was decayed by the application of the AC external magnetic field. In our previous work, we explained that the decay was due to the temperature rise of the HTS bulk caused by AC losses. In this paper, we adopted an analytic model to evaluate the decay of the critical current density of the bulk. And based on the analytic results and the Bean critical-state model, we calculated the guidance force as a function of times. Compared with the experimental results, the calculation results have almost the same trend and can qualitatively reveal the characteristics of guidance force of HTS bulk in this situation. Therefore, the guidance force decay of HTS bulk in the maglev vehicle system can be evaluated simply by this numerical method.

Superconducting maglev vehicle is one of the most promising applications of HTS bulks. In such a system, the HTS bulks are always exposed to time-varying external magnetic field, which is generated by the inhomogeneous surface magnetic field of the NdFeB guideway. So it is required to study whether the guidance force of the bulks is influenced by the inhomogeneity. In this paper, we studied the characteristics of the guidance force relaxation between the HTS bulk and the NdFeB guideway by an experiment in which 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. From the experiment results, it was found that the guidance force was decreased with the application of the AC external magnetic field, and the decay increased with the amplitude and was almost independent of the frequency.

Superconducting maglev vehicle system requires that the surface magnetic field of the guideway is uniform along the forward direction. But in practice the surface magnetic field of the NdFeB permanent magnet guideway is not always immutable. So the HTS bulks in this case are exposed to AC external magnetic field, which may induce the energy loss in the bulk and influence the guidance force between the HTS bulks and the NdFeB guideway. In this paper, we experimentally studied the influence of the AC external magnetic field perturbation on the guidance force of a HTS bulk over the NdFeB guideway. The experimental results showed that the guidance force was influenced by the application of the AC external magnetic. The guidance fore hysteresis became more evident with the amplitude of the AC field and was independent of the frequency in the range 90–400 Hz. We attributed the reason to magnetic hysteresis loss in the superconductor.

Superconducting maglev vehicle system was one of the most promising applications of HTS bulks. The NdFeB guideway in this system was composed of many NdFeB permanent magnets and screws, so the air gaps (airgaps) between two permanent magnets and the screws would result in the inhomogeneity of the surface magnetic field. In this paper, we studied the magnetic inhomogeneity over the permanent magnet guideway (PMG) used in high-temperature superconducting (HTS) maglev vehicle system and its influence on the levitation force of the HTS bulk. Firstly, we measured the transverse magnetic field above the airgap, the screw and the place under where there was no airgap and screw. It was found that the magnetic field 10 mm above the guideway was roughly uniform. Secondly, we investigated the influence of the magnetic inhomogeneity of the PMG on levitation force of the bulk superconductor. From the experiment results, we found that the influence was very small, and would be ignored. Therefore, we could conclude that the PMG made by this method satisfied the requirements of the HTS maglev vehicle system in a quasi-static state.