• Electrical & Electronic Materials
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• v.7 no.3
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• pp.262-270
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• 1994

미국의 ASC(American Superconductor Corp.)에서는 산화물계의 고온초전도선재를 대량생산하기 위한 대규모 투자를 계획하고 있으며 지금은 금속계 초전도선재처럼 장척의 고온초전도선재도 구매할 수 있는 시대로 접어들고 있다. 고온초전도체 벌크 및 박막의 경우도 새로운 프로세스들이 계속 시도되고 최적화 연구가 성과를 거두면서 고성능, 고품질의 재료들이 제조되고 있고 이것들을 이용한 상용화 연구개발이 미국, 일본을 중심으로 활발하게 이루어지고 있다. 최근 5년간의 고온초전도 분야에 대한 미국 연방정부의 연구비 투자 상황을 살펴보면 계속 증가추세에 있으며 벤처 비지니스의 민간기업들이 고온초전도체를 상용화하기 위한 많은 투자와 노력을 하고 있다. 고온초전도체는 그 사용 용도에 따라 벌크, 박막, 선재 등 다양한 형태로 만들어지고 있다. 본 고에서는 고온초전도체의 여러 연구분야 중 이론, 물성보다는 주로 응용기술적인 차원에서 재료 형태별로 최근의 연구개발 동향을 살펴보고자 한다.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.37 no.12
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• pp.872-878
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• 1988

During the past few years, a great deal of attention has been directed to the application of superconductivity to the electrical systems such as superconducting power transmission lines, superconducting magnet energy storage and so on. Yet in order to develop the practical model of these electrical equiqments utilizing suprconductivety and other phenomena at cryogenic temperautre, it is necessary to know the dielectric behaviour of insulating materials at cryogenic temperature in view of reliability, safety and economy of these machines. Investigation of dielectric properties of cryogenic liquids is very important due to the dual role of those as the dielectric and cooling medium. In this study, we investigated results measured over several kinds of dielectric characteristics of liquid nitrogen taking into consideration for application of high Tc superconductor. Dependence of breakdown voltage of gap width, polarity and pressure is reported in this paper and time delay characteristics of breakdown is also the subject of this discussion.

• Progress in Superconductivity and Cryogenics
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• v.7 no.1
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• pp.32-36
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• 2005

With the successful commercialization of Bi-2223 powder-in-tube wire , various attempts in the R & D of the high-Tc superconducting (HTS) magnets for high magnetic field applications are being implemented actively. Operating temperature of HTS magnet has to be maintained at the designed level but the magnetic energy and mechanical disturbance can cause unstable operational temperature of HTS magnet. Especially the generated heat energy of inner HTS winding Is apt to be accumulated . so the normal region appears in HTS winding. This paper deals with the quenching characteristics of three kinds of selected Bi-2223 wires : the High Current Density Wire (HC-A) and the High Strength Wire (HS-A) made by AMSC and HTS wire(HW-I) made by Innost The Innost wire has the highest minimum quench energy (MQE). The High Current Density Wire has the highest normal zone Propagation velocity (NZPV).

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1996.10a
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• pp.202-206
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• 1996

An experimental study of the characteristics of the repulsiveytype magnetic bearing using high Tc superconductor is presented. In field cooling superconductor has the position-stability due to a flux pinning effect and the strong damping due to hysterisis, while in zero field cooling it has the only strong repulsive force due to Meissner effect. Lift force in superconducting levitation has a hysterisis characteristics, and it is the dissipation of energy, the mechanism of damping. As the relative linear velocity between a magnet and a superconductor increases, the area of the hysterisis loop becomes smaller. It means the decrease of damping. In field cooling, the static stiffness is very nonlinear in smaller than initial gap, but almost linear in larger than initial gap.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.189-191
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• 1994

YBCO bulks for levitation have fabricated using MPMG method. The superconducting properties and repulsive/attractive force against permanent magnet were investigated for the specimens annealed at various periods after MPMG. A linear induction motor type levitation - traveling vehicle using the pinning force of MPMG processed YBCO bulk has fabricated. The floating or hanging small vehicle mounted with two YBCO pellets was confirmed to travel stabley on the Nd-Fe-B permanent magnet track. The traveling speed of the vehicle was confirmed to depend on AC frequency linearly. At 200 Hz, the travel ins speed was found to be 110 cm/sec.

• Electrical & Electronic Materials
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• v.9 no.3
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• pp.304-309
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• 1996

본 고에서는 초전도에 관한 학문적 연구내용의 추이와 그 응용기술의 개발내용을 간략히 살펴보았다. 고온 초전도의 형성원리에 대한 학문적 관심과 응용기술 개발사이의 괴리를 이해하려는 노력의 일환으로 고온 초전도체를 주대상으로 한 각종 연구결과들을 소개하면서 순수학문과 공학기술과의 긴밀한 연관성을 찾았다. 전자와 정공의 도핑 대칭성을 확립한 Nd-Ce-Cu-O의 발견은 물성의 정확한 이해에 기초한 성공이었고, 산화물 고온 초전도체들의 전자쌍 파동함수의 대칭성에 관한 논의들에서 최근 연구의 주종을 이루고 있는 Josephson-coupling과 Photoemission등의 직관적인 결과를 주는 측정 실험들은 고도의 첨단기술과 죠셉슨 접합 등의 새로운 초전도 물성개념의 정확한 이해를 요하는 연구들이었다. 이러한 새로운 초전도 개념들의 토대위에 현 응용분야들의 추세를 대략 살핌으로써 부실하나마 미래의 차원 높은 수요에 대비한 학문적, 기술적 준비를 시도해 보았다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.358-359
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• 2008

The heat generated in the high-Tc superconducting (HTS) devices is related with the cost efficiency and safe factor of HTS devices. This paper deals with the quench at the conduction-cooled joint between the HTS wire and copper terminals. The 3-D numerical simulation of this phenomenon was implemented and compared with the experimental results. The experiment was implemented with the HTS wire mounted on the copper blocks cooled with a Gifford McMahon (GM) cryocooler.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.697-698
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• 2006

고온 초전도 선재는 자장의 세기, 방향 그리고 온도에 따라 임계전류가 달라지는 특성이 있다. 임계전류가 달라지는 특성은 초전도 선재를 사용하는 초전도 기기에 매우 영향을 미치게 된다. 자장의 세기, 인가 방향이 선재의 임계전류에 비치는 영향에 대하여 알아보기 위하여, prototype magnet을 제작하고, 선재에 전압 tap을 부착하여 실험을 하였다. 자장의 세기와 고온 초전도 선재가 받는 자장의 방향을 변화시켜가며 실험을 하였다. 또한, 주파수에 대한 선재의 영향을 알아보기 위하여, 주파수 변화에 따른 선재의 임계전류 변화도 측정을 하였다. 본 논문은 고온 초전도 선재를 이용하여 제작하게 되는 고온 초전도 기기 설계의 기초자료로 활용될 수 있을 것이다.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.7
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• pp.437-443
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• 2004

In this work the AC loss measurement setup based on an iron core background magnet, not used in a conventional one, has been successfully developed. To prove its validity, a round-robin test for the same Bi-2223 tape sample among three institutes has been done. The results show that the self-field and magnetization losses from the developed setup well agree with the losses measured at two other institutes of Korea Basic Science Institute and Yokohama National University. The measured magnetization losses for parallel or perpendicular fields can be well predicted from the slab model or the strip model for a filamentary region. However the magnetization losses for longitudinal fields can be rather predicted by the slab model for a decoupled filament. The self-field losses are well explained by the Norris ellipse model.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.2
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• pp.111-114
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• 2017

In this research, the development of fabrication technique of bulk YBaCuO superconductors for application was studied. In fluence of $BaZrO_3$ addition on magnetization characteristics of thermal pyrolysis textured YBaCuO superconductor was investigated. Fine $BaZrO_3$ particle were dispersed within the textured YBaCuO matrix by means of the thermal pyrolysis processing. Magnetic levitation force for YBaCuO superconductors were obtained using Nd-B-Fe permanent magnet, at 77 K and at the magnetic field from 0 to 5.3 K gauss. In the unadded superconductor and 5 wt% $BaZrO_3$ addition, anomalous magnetization behavior, which is characterized by the intermediate magnetic field, was observed at 77 K. Critical current density was about few hundreds $A/cm^2$ and the magnetic characteristics increased slightly by addition of $BaZrO_3$ powder. Maximum magnetic force was obtained in the YBaCuO superconducting bulk with 3 wt.% $BaZrO_3$ addition.