Trapped Flux and Levitation Properties of Multiseeded YBCO Bulks for HTS Magnetic Device Applications—Part II: Practical and Achievable Performance

Abstract

After clarifying the essential characteristics of the multiseeded YBCO bulk in the previous work, that is, the existence of strongly connected or coupled grain boundaries between two grains by means of intergrain super current with a big flowing loop size, this paper proceeds to report its achievable performance in actual excitation conditions by working as trapped-field magnets or levitation devices. Besides evaluation of the trapped-flux characteristics by two most popular excitation methods, namely, static field-cooling magnetization (FCM) and pulsed-field magnetization in liquid nitrogen (LN2), the trapped-flux capability at lower temperatures up to 30 K, an interesting temperature for present superconducting machine applications, is also reported. From LN2 temperature to 30 K, the trapped flux with over six times improvement from 0.64 to 3.91 T was observed by FCM, at the same time along with a much decreased relaxation rate from 13.7% to 0.9% in 1-h measurements. In the aspect of levitation applications, the magnetic force density (both levitation force and guidance force, two most important performance parameters for maglev) above a permanent magnet guideway with Halbach style is measured and found to be able to promote the loading and stability performance of the first high-temperature superconducting maglev test vehicle simultaneously. As the multiseeding technique of the top-seeded melt-growth process has provided a promising way to fabricate bulk superconductors with large size, time saving and cost reduction, the presented trapped-flux and magnetic force results may help to comprehend, refer, and finally make better use of the multiseeded bulks in the large-scale superconducting magnetic devices.

Thermal behavior of flux jumps and influence of pulse-shape on the trapped field during pulsed magnetization of a high-temperature superconductor

“…Modern high-temperature superconductors (HTSs) exhibit large potential for new technologies. Superconducting trapped-field (TF) magnets could significantly reduce the size and enhance the performance of numerous magnetic devices such as (but not restricted to) motors and wind power generators [1][2][3][4][5][6][7][8], flywheels and maglev trains [1,[9][10][11], and the magnetic resonance imaging [1,[12][13][14][15]. To obtain such a magnet, one needs a method that would, ideally, provide maximum TF of high uniformity with minimum cash and energy cost.…”

Levitation performance of an onboard high-temperature superconducting bulk unit with cryocooler direct cooling

“…The size of each bulk is 64, 32 and 13 mm in length, width and thickness, respectively. The HTS bulks were manufactured by ATZ GmbH (Germany), which have superior performance across the seeds [13,14]. The permanent magnet guideway (PMG) consists of rectangular NdFeB permanent magnets arranged in a Halbach array.…”

Enhancing magnetic levitation and guidance force and weight efficiency of high‐temperature superconducting maglev systems by using sliced bulk YBCO

“…18,19,22 Different studies have been performed to enhance the superconducting material properties in addition to the size of the bulk REBCO, such as using a cylindrical 23,24 or pyramid-like 25 buffer layer between the seed and the main material. Notwithstanding the numerous number of studies done so far, the most commonly used bulk YBCO in Maglev studies of laboratory scale 14,15,26 or real-scale prototypes 5,27 are the ones fabricated by ATZ GmbH 8,22,[28][29][30] in a rectangular prism shape with three seeds.…”