Trapped Field and Levitation Performance of a YBCO Superconductor Magnetized in Different External Magnetic Fields

Abstract

In order to find a relative preferable method to improve the trapped magnetic field (Btrap) of a YBCO superconductor, the influences of field-cooling height (FCH), magnetization intensity, and magnetization process on the trapped fields of the high temperature superconductor (HTS) magnetized in the magnetic fields of the permanent magnet guideway (PMG) and the superconducting magnet (SM) were both studied. In addition, the levitation forces of the bulk magnetized in the two different magnetic fields were also investigated in this paper. The experimental results showed that the maximum trapped field ratio (δtrap) of the bulk magnetized above the PMG attained the largest value, when the initial FCH was 30 mm. The remagnetization process was a preferable method to increase the Btrap, in the case that the FCH was higher than 30 mm. When the exciting current (Ie) of the SM was smaller than 15 A, the remagnetization process was an effective method to improve the Btrap. The remagnetization performance of the bulk attained the saturation, under the condition that the Ie was larger than 15 A. In the aspect of the levitation performance, it can be found that the decreasing amplitude of the force with the Btrap became larger, when the levitation gap was lower. The force acted on the bulk increased with increasing the magnetic fields of the SM. Moreover, the results also indicated that the initial Btrap was larger; the maximum levitation force (Flmax) became smaller. The magnetic hysteresis of the bulk was found to decrease with increasing the Btrap.