Pulsed Field Magnetization Properties of Bulk RE-Ba-Cu-O as Pole-Field Magnets for HTS Rotating Machines

Abstract

Aiming at exploiting the high trapped field ability of bulk high-temperature RE-Ba-Cu-O (RE: rare-earth elements) superconductors, a brushless axial-gap type superconducting synchronous motor has been successfully developed as a technology demonstrator using eight melt-textured GdBa 2 Cu 3 O y (Gd-123) bulks as pole-field magnets. An output power of 10 kW at 720 rpm was realized by an average trapped field peak of 0.56 T reaching the armature coils, under a pulsed field excitation at the liquid nitrogen temperature. For such motors, to improve the trapped flux of bulks is a direct way to enhance the motor performance. In order to obtain a high trapped flux density with a regular shape for a high performance motor utilization, the pulsed field magne- tization (PFM) properties of two kinds of bulk superconductors have been investigated. By a reasonable multi-PFM process with a pair of vortex-type pulsed coils, it was found that the multi-seed Y-Ba-Cu-O bulk can bring a high average trapped field, while the single-grain Gd-Ba-Cu-O bulk under a size-adjustable pulsed coilcan obtain a very regular trapped field distribution. These results will be useful to the following optimization of the rotating machine system.Index Terms-High temperature superconductors, pole-field magnets, pulsed field magnetization, rotating machines, trapped field.

Influence of grain boundary connectivity on the trapped magnetic flux of multi-seeded bulk superconductors

“…This can be explained by the extra contributions of the inter-grain supercurrent flowing across the GB with a big loop size, in addition to the intra-grain supercurrent circulating in each grain of the multi-seeded bulk. The detailed discussion is reported elsewhere [16]. Even regarding to the uncut multi-seeded bulk No.…”

Relaxation Properties of the Trapped Flux of Bulk High-Temperature Superconductors at Different Magnetization Levels

“…Two bulk samples were employed in the experiments, one of which was a cylindrical single-grain GdBCO bulk (∅ 60 × 20 mm 2 ), fabricated by Nippon Steel Corporation (NSC) in Japan; the other one was a rectangular three-seeded YBCO bulk (66 × 34 × 15 mm 3 ), fabricated by ATZ Company in Germany. Both of them showed a good crystal growth, that is, a well-dressed cone-like trapped flux distribution for each grain after FCM [15,16]; accordingly, the peak trapped flux density appeared at the bulk center or seed positions. A cryogenic Bell Hall sensor (BHT921) was attached on the center of the seed surface with a gap of 0.3 mm to measure the peak field signal in real-time.…”

Вихревая Структура ВТСП В Неоднородном Магнитном Поле

“…Различные эффекты, такие как рост критического тока с увеличением магнитного поля, что проявляется в уширении петли перемагничивания образца [2], практически полностью определяются структурой и динамикой вихревой решетки. Сверхпроводящие образцы, а также кабели и ленты на основе ВТСП используются в сверхпроводящих магнитах [3], ограничителях тока [4,5] и в левитационной технологии [6][7][8]. В последнем случае используется магнитолевитационная система сверхпроводник -постоянный магнит, в которой сверхпроводник находится в градиентном поле постоянного магнита.…”