• 한국초전도ㆍ저온공학회논문지
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• 제21권4호
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• pp.59-63
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• 2019

To reduce the fault current below the current capacity of a circuit breaker, researches on HTS (High Temperature Superconductor) power cables with fault current limiting (FCL) function are increasing. An FCL HTS power cable transports current with low a impedance during normal operation. Yet, it limits the fault current by an increased inductive or resistive impedance of conducting layer when quench occurs at the FCL HTS power cable by the large fault current. An inductive type FCL HTS power cable uses increased inductive impendence caused by leakage magnetic flux outside the cable core when the quench occurs at a shield layer losing the magnetic shielding effect. Therefore, it has an advantage of less resistive heating than resistive type FCL HTS power cable and temperature increase is suppressed. This paper describes an ideal circuit model for the FCL HTS power cable to investigate the effectiveness of increased inductive impedance when quench occurs at the shield layer. Then, FEM analysis is presented with a simplified model cable composed of various iron yokes to investigate the effect of the shape of yoke on the generation of the inductive impedance.

• 한국재료학회지
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• 제4권7호
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• pp.828-836
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• 1994

YBCO산화물초전도체의 고온변형 특성을 조사하기 위하여 $890^{\circ}C$ ~ $930^{\circ}C$의 온도범위에서 $1.0 x 10^{-5}s^{-1}\sim 1.0^{-4}s^{-1}$의초기변형속도로 압축시험을 수행하였다. 변형온도가 증가함에 따라 또한 초기변형속도가 감소함에 따라 flow stress는 감소하였다. 변형률속도 민감지수는 0.41-0.46이었다. 이는 초소성 변형이 일어났음을 보여준다. 초소성변형에 대한 활성화 에너지는 약 500 ~ 580KJ/mol이었으며 Ag첨가량이 증가할수록 활성화에너지는 감소하였다. 초소성변형된 시편들의 미세조직 관찰결과 변형중에 결정립 성장이 일어났으며 Ag양이 증가함에 따라 이러한 현상을 뚜렷하였다. 변형후 결정립 형태는 등축상을 유지하였다. 이러한 결과로 볼때, YBCO 초전도체의고온변형기구는 확산을 동반한 결정립계 미끄러짐으로써 그 비율은 전 변형량중 약 65%정도였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 추계학술대회논문집
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• pp.273-276
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• 2003

High-temperature superconduction materials(Bi2223) possess electrical/electronic and magnetic properties. Because high-temperature superconduction materials is a ceramic powder, that can not be produced singlehandedly. So Ag sheathed Bi-2223 wire was produced by drawing process using powder-in-tube(PIT) method. This superconductor has many difficulties to produce. The main difficulty is that the mechanical properties of the ceramic powder are very different from those of the Ag sheath. Bi2223 high-temperature superconductivity have a single filament drawing process, and multi-filament drawing process. This study analysed multi-filament drawing process by FEM, a defects during multi-filament drawing was studied by FEM.

• 한국초전도ㆍ저온공학회논문지
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• 제3권1호
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• pp.35-39
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• 2001

The optimum cross-sectional area profile of gas-cooled high-temperature superconductor(HTS) current lead is analyzed to have minimum helium boil-off rate. The conventional constant area HTS lead has much higher helium consumption than the optimum HTS lead considered in this study. The optimum HTS lead has variable cross-sectional area to have constant satiety factor. An analytical formula of optimum shape of lead and temperature profile are obtained. For multi-stacking HTS current leads, the optimum tape lengths and minimum heat dissipation rate are also formulated. The developed formulations are applied to the Bi-2223 material, and the differences between constant area, constant safety-factor, and multi-stacking current leads are discussed.

• 대한전기학회논문지
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• 제41권7호
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• pp.766-772
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• 1992

Bi-Sr-Ca-Cu-O superconducting system has both the low and high Tc phases. We added Pb and sintered for 200hrs. in OS12T atmosphere in order to get the superconductor above critical temperature 100K. Superconducting properties of the Bi(Pb)SrCaCuO system doped Sb were also investigated. When Sb of 0.1mol is added, the sintering time becomes shorter than that doped Pb only. We could get the critical temperature 102K at the samples sintered for 24hrs. and 109K for 210hrs.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1992년도 춘계학술대회 논문집
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• pp.64-69
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• 1992

Bi-Sr-Ca-Cu-O superconducting system have the low and high Tc phases. In order to get the superconductor above crtitical temperature 100K, we added with Pb and sintered for a long time about 200 hrs. In this study, the influence of superconducting characteristics on the Bi(Pb)SrCaCuO system characteristics on the Bi(Pb)SrCaCuO system dopped Sb was investigate too. Adding Sb of 0.1 mol, the sintering time is short than that dopped Pb only. We could get the critical temperature 102 K at sintered for 24 hrs and 109 K for 210 hrs.

• 한국초전도ㆍ저온공학회논문지
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• 제11권3호
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• pp.6-9
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• 2009

The thermal characteristics of quench propagation is a crucial problem for the stability of the superconductor. The objective of this study is to simulate the quench propagation with the variation of disturbance energy in Bi-2223/Ag HTS pancake coil. In this analysis, the temperature-time trace of a point away from heater was calculated under conditions of different quench energy. The critical disturbance energy between quench propagation and quench recovering was calculated, In addition, the minimum quench energy with different transport currents was obtained through the present simulation. These results are significant to the application of HTS.

• Progress in Superconductivity
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• 제7권2호
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• pp.179-183
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• 2006

As a material for SFCL(Superconducting Fault Current Limiter), BSCCO tube with metal stabilizer is a promising candidate, assuring the stability and large power capacity, For the application, the proper soldering technique, which overcome the difficulties of the joining between BSCCO and metal stabilizer, is required. In this study, after soldering In-Bi solder and In-Sn solder with BSCCO superconductor, welding properties between BSCCO and solders were investigated. Because ceramic materials is difficult to weld, Ag electro-plating on BSCCO 2212 is used for intermetallic layer. To find out the best welding condition for superconductor, soldering is tested in the maximum temperature from $155^{\circ}C\;to\;165^{\circ}C$ in the reflow oven. By investigating the composition and thickness of IMC (lntermetallic Compound) created in the reaction of Ag with solder, we analyzed the welding properties of High-Tc superconductor from a micro point of view.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.265-266
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• 2006

Superconductor is developed for applications in high-power devices such as power-transmission cables, transformers, motor and generators. In such applications, HTS tapes are subjected to various kinds of stress or strain. In the fabrication of the devices, the critical current (Ic) of the high temperature superconductor degrades due to many reasons including the tension applied by bending, twist and thermal contraction. In particular manufactured HTS cable, we need pitch angle controls. This paper is analyzed that Ic characteristics is changed pitch angle of HTS tape. These results will amount the most important basis data in HTS cable.

• 한국초전도ㆍ저온공학회논문지
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• 제9권4호
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• pp.41-45
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• 2007

Superconductor is developed for applications in high-power devices such as power-transmission cables, transformers, motor and generators. In such applications, HTS tapes are subjected to various kinds of stress or strain. AC loss is also important consideration for many large-scale superconducting devices. In the fabrication of the devices, the critical current $(I_c)$ of the high temperature superconductor degrades due to many reasons including the tension applied by bending and thermal contraction. These bending or tension reduces the $I_c$ of superconducting wire and the $I_c$ degradation affects the AC loss of the wire. The $I_c$ degradation and AC loss (self field loss) of Bi-2223 HTS and Coated conductor were measured under tension and bending conditions at 77K and self-field.