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.

Thermomagnetic instability and accompanied stress intensity factor jumps in type-II superconducting bulks under various magnetization processes

“…Clearly, the system with thermomagnetic interaction is coupled by the initial-boundary problem of equations ( 5)- (10). Here, a discretization method that previously used in [44][45][46] is adopted to solve the coupling problem. We discretize the bulk SC into N = a SC /∆x × b SC /∆y elements along the length with a rectangular cross-sectional area ∆S = ∆x × ∆y, and assume that the current density is uniform in each element.…”

“…and defining appropriate weighting functions, a weak form of equation ( 5) at element i is obtained [44][45][46]…”

“…After the numerical model is established, the thermomagnetic characteristics of the SC can be analyzed by performing an iterative algorithm, as shown in figure 1(b). The numerical procedure is described in detail in [44][45][46], and it is not repeated here. Based on the obtained current distribution, the horizontal and vertical components of the magnetization for the SC can be calculated as [47]…”

Highly Porous Superconductors: Synthesis, Research, and Prospects

“…The use of PSs in these devices should provide additional advantages in ensuring stable operation and reducing weight. For some problems, e.g., to increase the dynamic stability during magnetic levitation [146], a combination of porous and dense superconductors may be a good solution.…”

Angular dependence of vertical force and torque when magnetic dipole moves vertically above flat high-temperature superconductor*

“…[4][5][6] At the same time, a large number of studies have been performed to improve the levitation performances including vertical force, lateral force, magnetic stiffness, etc. [7][8][9][10][11][12][13] In addition, it has been found experimentally that the angle between the magnetization direction of the PM and the c axis of the HTS significantly affects the levitation properties. [14][15][16][17][18] In fact, the magnetization direction of the PM does not often coincide with the c axis of the HTS in many practical applications.…”