Strategies to improve the dynamic levitation performance of superconducting maglevs against force decay and disturbance

Abstract

In the design of maglev systems, the levitation force determines the levitation height and the dynamic stability associated with potential vibrations, especially the offset of the levitation point relative to the working point. However, such two key parameters are often antagonistic: a relatively low dynamic stability comes with a high levitation force, whereas a relatively low levitation force can come with a high dynamic stability. In this paper, we will discuss several strategies to deal with this problem by means of a two-dimensional numerical model based on Newton's second law and Maxwell's equations together with a power-law constitutive relation. The dynamics of maglev systems consisting of a bulk high-temperature superconductor and a Halbach-type permanent-magnet guideway with soft ferromagnets are analyzed. The results show that the drift phenomenon occurs in both vertical and lateral directions triggered by a transverse disturbance, and preloading can alleviate such a phenomenon, but this will lead to a reduction in the levitation force. Improved preloading is effective in enhancing the levitation force without sacrificing the dynamic stability. In some systems, the levitation force and dynamic stability can be further improved by adjusting the soft ferromagnets to an appropriate location in the guideway. Moreover, some guidelines on how the superconducting part should be designed are provided in order to overcome the technical difficulty and reduce the material consumption while at the same time maintaining the dynamic levitation performance.