Levitation Height Drifts of HTS Bulks under a Long-Term External Disturbance

Abstract

High-temperature superconducting (HTS) maglev owns the capability of passive stabilization and has the potential to operate at a high speed with low energy consumption. However, the excitation caused by the irregular surface and inhomogeneous magnetic field of the permanent magnet guideway (PMG) will result in vibration between the superconductors and PMG, which could lead to some stability problems such as drift. To study the reliability of HTS maglev systems under a long-term disturbance, a tailored experimental device composed of a vibration table, a fixture, and HTS maglev model was employed. The effects of field-cooling height (FCH), external excitation frequencies, and amplitudes on the levitation height drift were investigated. It is found that under the same operating conditions, large excitation amplitude, high frequency, and low FCH would lead to a greater levitation height drift. There are three kinds of drift trends, i.e., downward, upward, or downward at first and then upward, and the phenomenon of drifting upward is more likely to occur under small excitation amplitude, high frequency, and low FCH conditions. Meanwhile, two simulation models employing the flux flow model and the flux flow and creep model were applied respectively. The simulation results show that the flux flow and creep model are more consistent with the experimental phenomena and the flux flow has a greater influence on the drift in the initial time period, while the flux creep has a slighter impact on the drift for a long time. These researches reveal the levitation height drift rules of the HTS maglev system and introduce proper simulation model for levitation height drift so that this work provides a reference for the design and safe operation of HTS maglev vehicles.