• 한국초전도ㆍ저온공학회논문지
• /
• 제12권1호
• /
• pp.32-36
• /
• 2010

Superconducting current leads are indispensible for reducing power loss when subjecting current into superconducting magnets. HTS(High-Tc superconducting) current leads are divided into two types; one is bulk type and the other is tape type. In this paper, conceptual design on the HTS current leads which adopts tape type for nuclear fusion magnets is carried out using magnetic field analysis and thermal analysis. When large current flows through superconducting current leads, strong self magnetic field is generated and applied to the superconducting tapes. This phenomenon leads to the critical current decrease of the superconducting tape. Therefore, we analyzed magnetic field distribution of current leads and found the proper arrangement with respect to the various HTS tapes. In addition to the magnetic field analysis, heat leak through the current leads was also calculated to know which HTS tape is superior than others in thermal aspect. Magnetical field analysis and calculation of heat leak are performed to design 2 kA class HTS current leads.

• 한국초전도ㆍ저온공학회논문지
• /
• 제11권3호
• /
• pp.31-34
• /
• 2009

An HTS power cable is generally composed of 2 layers for conducting and 1 layer for shielding. For the analysis of AC loss of an HTS power cable, 2-dimensional magnetic field analysis is carried out. The magnetization loss in HTS cable core was calculated, and the transport current loss was obtained from the monoblock equation and the elliptical Norris Equation. And the total AC loss of the cable was expected by the sum of magnetization loss and transport current loss. The variation of ac loss with respect to the gap and uncertain factor between the superconducting tapes was investigated, and the ac loss of 22.9kV/50MVA high-Tc superconducting power cable was calculated. These results well agree with those of experiment.

• 한국초전도ㆍ저온공학회논문지
• /
• 제2권1호
• /
• pp.35-35
• /
• 2000

The main issues for the power application of High Tc superconducting tape are lower AC loss and higher stability conditions. HTS tape has large stability margin by high heat capacity of superconductor itself and high temperature margin. But, it can be damaged by continuous heat generation at quench point, because normal zone propagation velocity by generating heat is very low. Here, we analyze the quench propagation characteristics using finite element method for BSCCO-2223 HTS tape.

• Progress in Superconductivity
• /
• 제1권2호
• /
• pp.85-88
• /
• 2000

The temperature dependent Josephson critical current $J_c(T)/J_c(0)$ between high $T_c$ superconductors along the a-axis is theoretically studied. The interface influence on the wave functions of quasi-particles is included in the theory within the framework of the two-dimensional t-J model. It is found that the experimental results can be satisfactorily explained by the present model with d wave pairing symmetry.

• 한국초전도학회:학술대회논문집
• /
• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
• /
• pp.401-404
• /
• 1999

본 논문은 고온초전도한류기가 투입된 회로에 사고가 발생했을 경우 사고각에 따른 사고전류의 패턴에 관한 연구이다. 계통에 심각한 영향을 끼치는 이러한 사고전류의 순간 특성을 해석하기 위해 유도형 고온초전도한류기를 직접 제작하였으며 임의로 다른 각도에서 사고를 발생시켜 실험하였다. 임의의 사고각을 위해 triac으로 구성되어있는 위상각제어 및 사고 발생기를 부하와 직렬로 연결하였다. 또한, 순간적으로 큰 사고전류의 유입은 철심을 포화시키기에 충분하며 철심의 포화로 인해 상대투자율이 작아짐으로서 고온초전도한류기의 임피던스가 작게 발생하게 된다. 본 논문에서는 이러한 영향으로 인한 사고전류의 패턴에 관하여 연구하였다.

• 한국재료학회지
• /
• 제1권2호
• /
• pp.71-76
• /
• 1991

The superconducting powders in $YBa_2Cu_3O_{7-x}$ and Bi-Pb-Sr-Ca-Cu-O system were easily prepared from water in oil type emulsion by loading each cation into the aqueous phase. In $YBa_2Cu_3O_{7-x}$ system, the superconducting orthorhombic phase was formed by calcining at $750^{\circ}C$ for 10h in $O_2$. The size of the superconducting phase powders was submicron. The density of the sintered specimen using this powders was about 95% of the theoretical density and the resistance sharply decreases at about 90K, In Bi-Pb-Sr-Ca-Cu-O system the low Tc phase($(Bi, Pb)_2Sr_2Ca_1Cu_2O_y$) was formed by calcining at $800^{\circ}C$ for 10h in a low oxygen partial pressure of 1/20 atm The shape of clacined powder is thin plate of which size is about $2\mu\textrm{m}$ and thickness is smaller than $\mu\textrm{m}$. It was observed that the high Tc phase ($(Bi, Pb)_2Sr_2Ca_2Cu_3O_y$) was formed by sintering at $850^{\circ}C$ for 30h in oxygen pressure of 1/20 atm without intermediary grinding. The above sintered sample exhibited superconductivity with a Tc(zero)=105K.

• 한국초전도학회:학술대회논문집
• /
• 한국초전도학회 2000년도 High Temperature Superconductivity Vol.X
• /
• pp.9-14
• /
• 2000

We report on the novel nonequilibrium nlicrowave emission from quasiparticle-injected high-Tc superconductors. The phenomena have been observed for the current-injected YBCO/I/Au or BSCCO/I/Au thin-film tunnel junctions and BSCCO single-crystal intrinsic Josephson mesa junction samples. For the thin-film tunnel junctions, the emitted radiation appears as broadband. For the intrinsic BSCCO mesa samples, the radiation appears as three different modes of emissions depending on the bias point in the hysteretic current-voltage characteristics; Josephson-emission, nonequilibrium broad emission and sharp coherent microwave emission. The results were interpreted by the Josephson plasma excitation model due to quasiparticle injection.

• 전기학회논문지
• /
• 제56권1호
• /
• pp.128-131
• /
• 2007

YBaCuO superconducting ceramic thick films were fabricated by chemical process. YBaCuO films have been successfully grown on $SrTiO_3$ substrates without a template layer. The films show poor or non superconductivity although they have excellent crystalline properties. ion channeling measurement made it clear that the strain in the films due to strong chemical bonding between the substrate and epilayer remains, resulting in the poor superconductivity. The X ray diffraction pattern of the YBaCuO thick films contained 90K phase. The self template method have resolved this problem. We obtained high-Jc as-grown YBaCuO on $SrTiO_3$ (100).

• 한국초전도저온공학회:학술대회논문집
• /
• 한국초전도저온공학회 2001년도 학술대회 논문집
• /
• pp.68-71
• /
• 2001

This paper deals with the operational characteristics of the three-phase modified bridge type fault current limiter(FCL) for 3.3kV/200A power system. This is a preliminary step to develop the FCL's faculties for an application to high voltage transmission line. A three-phase modified bridge type FCL consists of transformers, diodes, and a high-Tc superconducting coil. As the results of simulations, when the FCL of 1.5H inductance was installed in the power system. the fault current was reduced to be about 90% of that without FCL.

• Progress in Superconductivity
• /
• 제3권1호
• /
• pp.74-77
• /
• 2001

We have fabricated a high-Tc superconductive transistor with polyvinylidene fluoride (PVDF) gate electrode on MgO bicrystal Josephson junction by spin-coating method. The PVDF ferroelectric film is found to be suitable fur a gate electrode of the superconductive transistor since it has not only small leakage current but also high dieletric constant at low temperature. For the application of superconducting-FET, we investigated millimeter wave properties (60 GHz band) of the Josephson junction with PVDF gate electrode.