• 제목/요약/키워드: Critical Current

검색결과 3,048건 처리시간 0.032초

Design and Fabrication of 5 T HTS Insert Magnet (5 T급 고온초전도마그넷의 설계 및 제작)

  • Ku, M.H.;Kim, D.L.;Choi, Y.S.;Cha, G.S.
    • Progress in Superconductivity and Cryogenics
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    • 제14권3호
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    • pp.28-32
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    • 2012
  • The critical current of the HTS(High Temperature Superconductor) tape is governed by cooling temperature, magnetic field and its angle to HTS tape originated from its geometrical structure. At the HTS coil design stage, the critical current of the coil is calculated by considering the Ic-B characteristics of the 2G tape and the operating current is determined based on the critical current. The operating current and the structure of the 5 T coil are suggested through the FEM (Finite Elements Method) analysis and calculation. As a part of our on-going research on a 20 T LTS/HTS magnet, we have designed and constructed a 5 T HTS insert coil and tested it in liquid helium temperature.

Superconducting Flux flow Transistor using Plasma Etching (플라즈마 식각을 이용한 초전도 자속 흐름 트랜지스터)

  • 강형곤;고석철;최명호;한윤봉;한병성
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • 제16권5호
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    • pp.424-428
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    • 2003
  • The channel of a superconducting flux flow transistor has been fabricated with plasma etching method using a inductively coupled plasma etching. The ICP conditions then were ICP Power of 450 W, rf chuck power of 150 W, the pressure in chamber of 5 mTorr, and Ar : Cl$_2$=1:1. Especially, over the 5 mTorr, the superconducting thin films were not etched. The channel etched by plasma gas showed the critical temperature over 85 K. The critical current of the SFFT was altered by varying the external applied current. As the external applied current increased from 0 to 12 mA, the critical current decreased from 28 to 22 mA. Then the obtained trans-resistance value was smaller than 0.1 $\Omega$ at a bias current of 40 mA.

Fabrication of Bi-2223 high-Tc superconducting current lead (Bi-2223 고온초전도 전류리드의 제조)

  • Ha, D.W.;Oh, S.S.;Ryu, K.S.;Chang, H.M.
    • Proceedings of the KIEE Conference
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    • 대한전기학회 1996년도 하계학술대회 논문집 C
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    • pp.1660-1662
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    • 1996
  • Superconducting current lead is one of the promising applications of the oxide high-Tc superconductors, because they have the advantage of decreasing heat conduction to low temperature region, comparing with a conventional cooper alloy lead. High critical current density is a key factor for the applications such as current lead. $(Bi,Pb)_{2}Sr_{2}Ca_{2}Cu_{3}O_{x}$ high Tc superconductor hase been investigated in terms of critical current density. Bi-2223 superconducting current lead made by CIP and solid state sintering process. Bi-2223 current lead that heat treated at $836\;^{\circ}C$ for 240 h in 1/13 $PO_2$ had over $500\;A/cm^2$ of critical current density at 77K. We knew that the superconducting properties of tube type current leads were better than rods type of them. And we investigated the relation of Bi-2223 formation and heat treatment condition by XRD and SEM analysis.

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Fabrication of a BSCCO Magnet and its Operating Characteristics of Current Compensation in Persistent Current Mode (BSCCO Magnet 제작 및 영구전류모드에서의 전류 보상 운전 특성)

  • Jo, Hyun-Chul;Chang, Ki-Sung;Jang, Jae-Young;Kim, Hyung-Jun;Chung, Yoon-Do;Yoon, Yong-Soo;Ko, Tae-Kuk
    • Progress in Superconductivity and Cryogenics
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    • 제12권1호
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    • pp.56-60
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    • 2010
  • Recently, many researches have been carried out for a high temperature superconducting (HTS) magnet which is advantageous in high critical current density and critical temperature. In HTS magnet, however, critical current is decreased by perpendicular magnetic field and persistent current is hard to maintain due to a low index value and high joint resistance compared with low temperature superconducting (LTS) magnet. In this paper, the HTS magnet using BSCCO wire was simulated through finite element method (FEM) and manufactured. we experimentally investigated operating characteristics of the compensating mode of the HTS magnet for current decay and made a comparison between persistent current mode and compensating mode. A feedback control unit was used to sustain current within specified ranges with defined upper and lower limits.

Angle-dependent modulation of the critical current of YBa$_2Cu_3O_7$ step-edge Josephson junctions on SrTiO$_3$ substrate (SrTio$_3$ 기판 위에 제작된 YBa$_2Cu_3O_7$ 계단형 모서리 조셉슨 접합의 각도에 따른 임계전류 특성)

  • Hwang, Yun-Seok;Moon, Sun-Kyung;Lee, Soon-Gul;Kim, Jin-Tae
    • 한국초전도학회:학술대회논문집
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    • 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
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    • pp.83-86
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    • 1999
  • We have fabricated $_2Cu_3O_7$ step-edge junctions with different step orientations and studied their transition properties. Steps with different orientations were prepared on the substrate. Josephson junctions were made on a single substrate with step orientations ranging from 0$^{\circ}$ to 165$^{\circ}$ at 15$^{\circ}$ interval. We measured current-voltage characteristics, the critical current, and the superconducting transition temperature as a function of the angle. The critical current showed a modulation that has a maximum near 0$^{\circ}$ or 90$^{\circ}$ and a minimum near 45$^{\circ}$ and 135$^{\circ}$. We believe that the critical current modulation with the step orientation could be associated with the symmetry of high T$_c$ superconductor.

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Non-contact critical current measurement using hall probe (Hall probe를 이용한 비접촉 임계전류 측정)

  • Kim, Ho-Sup;Lee, Nam-Jin;Ha, Dong-Woo;Baik, Seung-Kyu;Kim, Tae-Hyung;Ko, Rock-Kil;Ha, Hong-Soo;Oh, Sang-Soo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 한국전기전자재료학회 2009년도 춘계학술대회 논문집
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    • pp.7-8
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    • 2009
  • Non-contact critical current measurement apparatus was developed using hall probe which measures the magnetic field distribution across the width of superconducting tape. The hall probe consists of 7 independent hall sensors which lie in a line 600 ${\mu}m$. The difference between maximum and minimum magnetic field in the magnetic filed distribution is a main parameter to determine the critical current. As preliminary research, we calculated the magnetic field intensity at the middle sensor, which is a minimum magnetic field and generated by the circular shielding current modeled by Bean model. We confirmed that there are some parameters that affect on the minimum magnetic field; the distance between superconducting layer and hall sensor, the width of superconducting tape, and the critical current distribution across the width of superconducting tape. Among these parameters, the distance between superconducting layer and hall sensor highly influences on the minimum magnetic field.

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Study on current limiting characteristics of YBCO coated conductor with stainless steel stabilizer layer (스테인레스 안정화 층을 갖는 YBCO Coated Conductor의 전류 제한 특성에 관한 연구)

  • Du, Ho-Ik;Kim, Min-Ju;Du, Seung-Gyu;Kim, Yong-Jin;Lee, Dong-Hyeok;Han, Byoung-Sung
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 한국전기전자재료학회 2009년도 하계학술대회 논문집
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    • pp.365-366
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    • 2009
  • This study researched into the manufacture of current-limit module of using YBCO coated conductor. Regarding over-current of exceeding the critical current, the quench characteristics were researched according to the stabilizing layer through tendency in resistance, which is generated in conductor, by applying over-current to YBCO coated conductors, which have stabilizing layer. YBCO coated conductors, which were used in experiment, include one kind such as the conductor, which used stainless as the stabilizing layer. The critical current is 70 A. And, the critical temperature is with 90 K. First of all, the quench generation was researched under over-current of exceeding the critical current by using this YBCO coated conductors. The tendency of a rise in the detected voltage according to the applied current was measured. And, the tendency of a rise in resistance through voltage-current curve was measured. As a result, the point of time in thermal quench of conductor, which has stainless as the stabilizing layer, could be confirmed to be fast.

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Analysis on Linear Voltage Components of Joints Ag-sheathed BSCCO tapes (은 피복 BSCCO 선재 접합부의 선형전압성분 분석)

  • 황보훈;최세용;강준선;나완수;김정호;주진호
    • Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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    • 한국초전도저온공학회 2000년도 KIASC Conference 2000 / 2000년도 학술대회 논문집
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    • pp.166-169
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    • 2000
  • Usually, the critical current of jointed BSCCO tapes degrades quite a bit compared to the normal unjointed tape regions. It has been thought that the current redistribution around the jointed region is the main cause it. We experimentally found the linear voltage components around the jointed area, especially in the transition region, which suggests that the current redistribution around the jointed area is the main reason of the critical current degradations.

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Thermal Excitations in Nb Josephson Junctions (Nb 조셉슨 접합의 열적 여기현상)

  • 김동호;황준석
    • Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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    • 한국초전도저온공학회 2003년도 학술대회 논문집
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    • pp.75-77
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    • 2003
  • We have measured the escape rates of the Nb Josephson junction from its zero-voltage state. The critical current measurements were carried out in repeatedly sweeping the current-voltage characteristics of the junction with a current ramp. From the distribution of the critical current the escape temperature was determined by applying the thermal activation model.

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Time Delay of Quench Phenomenon in Superconducting wire (초전도선재의 퀜치현상의 시간지연)

  • Oh, B.H.;Hong, I.S.;Jin, H.B.;Ryu, K.S.;Lee, S.H.
    • Proceedings of the KIEE Conference
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    • 대한전기학회 1997년도 하계학술대회 논문집 A
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    • pp.270-272
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    • 1997
  • Superconducting wire is quenching as soon as transport current exceeded the critical current value. However transport current exceeded the critical current value, quench is not generated immediately. In this paper, the results of the theoretical study for time delay of quench phenomenon are described.

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