Magnetic levitation and guidance performance of Y–Ba–Cu–O and Gd–Ba–Cu–O bulk superconductors under low ambient pressure

Abstract

The high-temperature superconducting Maglev-evacuated tube transport (HTS Maglev-ETT) system has significant potential for practical applications. In order to employ HTS bulks in an ETT system, it is necessary to study the magnetic levitation and guidance performance of bulk superconductors under low ambient pressure conditions that are representative of those inside the tube. As a result, we have investigated the Maglev performance of Y–Ba–Cu–O (YBCO) and Gd–Ba–Cu–O (GdBCO) single grain, bulk superconductors under different ambient pressures of 100 kPa, 60 kPa and 20 kPa using a bespoke pressure-controlling platform, in which the superconductors were positioned above a Halbach permanent magnet guideway. The levitation forces under conditions of field-cooling (FC) and zero-field-cooling (ZFC) have been measured and analyzed. The guidance force for the FC case and the levitation force relaxation for the ZFC case were also measured. It was found from the experimental results that the Maglev performance of both types of bulk superconductor improves significantly by reducing the ambient pressure in their immediate working environment. The levitation forces of YBCO and GdBCO bulk superconductors were observed to increase by 11.6% and 4.4% in the case of FC, and by 20.3% and 13.7% in the case of ZFC, respectively, as the ambient pressure changed from 100 kPa to 20 kPa. An improvement of the guidance force and an inhibition of the levitation force relaxation were also observed for these materials. The supercooled liquid nitrogen cryogen in the low-pressure environment further reduces the temperature, which, in turn, increases the critical current density Jc of the bulk superconductors and improves their levitation performance. These results provide further evidence of the significant advantages of combining HTS Maglev with evacuated tube technologies as a key enabling feature of the HTS Maglev-ETT system. The data further indicate that YBCO bulk superconductors tend to be more sensitive to ambient pressure and temperature variation than GdBCO bulk superconductors. This difference essentially reflects the dependence of Maglev performance of HTS bulk superconductors on Jc when operating in a low-pressure environment.

Prediction models establishment and comparison for guiding force of high-temperature superconducting maglev based on deep learning algorithms

“…(c) Likewise, from the micro aspect in future guiding force prediction area for HTS maglev, the effect brought by high temperature superconductivity mechanism should also be considered carefully. Specifically, the influence factors related to mechanism and micro-structure such as interfaces of materials [62], preparation materials (YBaCuO, GdBaCuO) [63][64][65], dislocation situation [66,67], grain boundary condition [68][69][70] and type (bulk, tape, film) for high temperature superconductors utilized should be supposed to the features as well. And the consideration of these micro features will make the expression of HTS guiding force based deep learning algorithm become more authentic and universal.…”

Thermal-vibration correlation study for high-temperature superconducting maglev intelligent monitoring based on back propagation neural network analysis

“…Since the appearance of the world's first HTS maglev principle prototype [5], the application of the HTS maglev train has become global research focus [6][7][8][9]. At present, many studies have been carried out on the levitation force, guiding force, and stiffness under static and quasi-static conditions, and the engineering load capacity of the HTS maglev train has been already solved [10][11][12][13][14][15]. With the continuous research for engineering applications, especially the engineering prototype train and test line with a design speed of 620 km h −1 was opened in Chengdu, China [16], it is urgent to study the dynamic characteristics of the HTS maglev train at high speed.…”

Comparative study between electromagnet and permanent magnet rails for HTS maglev

“…Since the discovery of high temperature superconducting (HTS) phenomenon, HTS materials have attracted extensive interest in superconducting maglev studies [1][2][3][4][5][6][7][8][9] due to their unique properties. The interaction between an HTS bulk and a magnet guideway can produce both vertical levitation force and lateral guidance force, which is the unique feature of HTS maglev [10].…”