YBCO bulk of the superconducting bearing for a 10 kWh flywheel

Abstract

We have fabricated the stator of a superconducting bearing module for a 10 kWh class flywheel system. The bearing is of radial type in that YBCO bulks are installed in the inner stator and ring-shaped permanent magnets in the outer rotor. YBCO bulk superconductors have a Japanese roof tile shape with epoxy resin impregnation for reinforcement and surface protection. The inner stator is a cylinder (OD = 123 mm, ID = 93 mm, height = 60 mm) that consists of eight YBCO blocks. The c-axis of the YBCO blocks was parallel to the radial direction of the cylinder. The cylindrical set of the YBCO bulks was fixed in a cryostat with epoxy resin. Before installment, we measured the trapped magnetic field distribution of the individual YBCO bulks by using Hall probes at 77 K after field-cooled in the presence of 1 T. The peak field values ranged from 0.4 to 0.7 T. For some samples, the field distribution was not symmetrical, suggesting the presence of some cracks or defects. We also measured the repulsive force between the YBCO bulk at 77 K and a permanent magnet using a tensile machine with a permanent magnet 25 mm in diameter and 5 mm in thickness having surface induction of 0.3 T. Unlike the trapped field, the repulsive force was almost constant for all the samples and was about 50 N at a 0.5 mm gap.

Fabrication of Gd1.5Ba2Cu3O7-y Bulk Superconductors from the Powder Synthesized by a Solid-State Reaction Method

“…산화물 초전도체는 저항 제로를 이용하는 고효율 전력응용, 영구자석과 초전도체 간의 마이스너 반발력을 이용한 플라이휠 무접점 베어 링, 자기부상 운송과 같은 자기부상 응용, 초전도체 내 부에 자력을 포획시켜 영구자석으로 만들어 사용하는 초 전도 벌크자석과 자기분리기 등에 활용된다. [2][3][4] 희토류 산화물 초전도체 중에 가장 널리 사용되는 물 질은 이트륨을 원료로 사용하는 YBa 2 Cu 3 O 7-y 이다. 1 는 초전도 온도(93 K)가 이트륨계 초전도체 보다 높고, 자 기장에 대한 플럭스 피닝(Flux pinning) 특성이 탁월하 기 때문에 고자장에서의 응용에 유리하다.…”

Experimental Study of the Electromagnetic Forces of a HTS Bulk Magnet Subjected to Sinusoidal Traveling Magnetic Field

“…A high magnetic field increases the output power or reduces the size of a machine making them likely to substitute traditional magnets in a variety of engineering applications including superconducting maglev systems [2], [3], magnetic bearings [4], [5], motors [6], [7] and other ac devices. Such superconducting bulk magnets are subjected to ac external magnetic field in most engineering applications, especially in linear motors.…”

Interaction of bulk superconductors with flywheel rings made of multiple permanent magnets

“…Superconducting flywheel systems have already constructed by several groups [4][5][6][7][8][9]. In order to minimize the rotational loss, conventional flywheel rings for the superconducting system are made of a single piece like permanent magnet.…”