• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.112-114
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• 2001

The magnetic suspension of a high T$\sub$c/ BipbSrCaCuO superconductor beneath toroial Permanent magnet was examined by means of an improved magneto-balancing method at 77K. Both the experimental values of the suspending position and the force exerted upon the superconducting specimen were in good agreement with those calculated from the magnetization curve of the specimen and the magnetic field map of the used permanent magnet.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.388-389
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• 2006

Electro-deposition of carbon film on silicon substrate in methanol solution was carried out with various current density, solution temperature and electrode spacing between anode and cathode. The carbon films with smooth surface morphology and high electrical resistance were formed when the distance between electrode was relatively wider. The electrical resistance of the carbon films were independent of both current density and solution temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.389-392
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• 1996

The recent development of high temperature superconducting epitaxial thin film offer great potential for planar passive microwave application such as ring resonator, filters, transmission lines, and antennas. This paper describes the fundamental properties of Microstrip Band-Pass Filter using HTS Thin Film and its application to microwave devices. In order to fabricate HTS microstrip multiple filters, We have grown laser ablated HTS thin films, patterned by photolithographic process and wet etching processes intro HTS microwave devices.

• Electrical & Electronic Materials
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• v.5 no.1
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• pp.43-51
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• 1992

최근 에너지 절약면에서 초전도 케이블에 관심을 모으고 있다. 그러나 케이블의 수명과 신뢰성을 보장하기 위해서는 극저온 절연기술이 반드시 필요하다. 본 논문에서는 극적은 기체 질소의 절연파괴특성과 기구에 대해 보고한다. 극저온 기체 질소(300K-93K)의 절연파괴전압은 액체 질소(77K)의 경우의 1/4~1/6배정도 낮으며 온도와 기체밀도에 의존한다. 또한 비등점근처의 온도영역을 제외하고는 Paschen의 법칙이 성립한다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.7
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• pp.606-611
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• 2009

AC loss is one of the important factors for commercialization of a high temperature superconducting (HTS) cable from an economic point of view. But AC loss characteristics of the HTS-cable are not elucidated completely because of its complex structure. As an earlier stage of analyzing the AC loss in the 22.9 kV/50 MVA, 100m HTS-cable system of Korea Electric Power Corporation (KEPCO) which is now in collaboration with us, a two-dimensional (2D) numerical model, which takes into account the nonlinear conductivity properties of a high temperature superconductor, has been developed. In order to examine our 2D model, we have prepared several single-layer cable samples whose AC losses are sufficiently reliable due to their simple structure. The AC losses of the samples were experimentally investigated and then compared with our 2D model. The results show that the numerically calculated AC losses are not in good agreement with the measured ones for the cylindrical cable and deca-cable samples with low critical current density. However, the numerically calculated and measured AC losses are relatively in good agreement for the deca-cable and hex-cable samples with high critical current density, although the difference between these two loss data in the deca-cable sample tends to increase in the low current region.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.341-344
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• 2004

The superconducting properties of $YBa_2Cu_3O_x$ with different content impurities of PbO and $BaPbO_3$ were studied. When the PbO was used as an additive in $YBa_2Cu_3O_x$, although the melting point could be reduced, the superconductivity became poor. From the XRD pattern of the sintered mixture of $YBa_2Cu_3O_x$ and PbO it was known that there is a reaction between $YBa_2Cu_3O_x$ and PbO, and the product is $BaPbO_3$. In the process of the reaction the superconducting phase of $YBa_2Cu_3O_x$ was decreased and $BaPbO_3$ would be the main phase in the sample. Therefore, $BaPbO_3$ was chosen as the impurity additive for the comparative study. The single phase of $BaPbO_3$ was synthesized by the simple way from both mixtures of $BaCO_3$ and PbO, $BaCO_3$ and $PbO_2$. Different contents of $BaPbO_3$ (10%, 20%, 30%) were added in the $YBa_2Cu_3O_x$. By the Phase analysis in the XRD patterns it was proved that there was no reaction between $YBa_2Cu_3O_x$ and $BaPbO_3$. When $BaPbO_3$ was used as impurity in $YBa_2Cu_3O_x$ the superconductivity was much better than PbO as an impurity additive in $YBa_2Cu_3O_x$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.189-189
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• 2010

The Improved flux-lock type superconducting fault current limiter(SFCL) is composed of a series transformer and superconducting unit of the YBCO coated conductor. The primary and secondary coils in the transformer were wound in series each other through an iron core and the YBCO coated conductor was connected with secondary coil in parallel. In a normal condition, the flux generated from a primary coil is cancelled out by its structure and the zero resistance of the YBCO thin films. When a fault occurs, the resistance of the YBCO coated conductor was generated and the fault current was limited by the SFCL. In this paper, we investigated the fault current limiting characteristics through the spot at the beginning of the fault current in the Improved flux-lock type SFCL. The experiment results that the fault current limiting characteristics was difference according to the point of a fault current started. Through the analysis, it was shown that shorter the time of a phase transition.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.2
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• pp.106-110
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• 2017

This paper compared current limiting characteristics of superconducting fault current limiter (SFCL) using E-I core due to the location of windings. Since E-I core has three legs and two magnetic paths, the current limiting characteristics of SFCL were expected to be affected by the installation location of windings, either center leg or right/left leg. To analyze its characteristics, the electrical equivalent circuit of the SFCL were derived and the electromagnetic analysis for the SFCL with the designed structure were performed. From the short-circuit tests, the hysteresis curve and the voltage-current trajectory of the SFCL due to the installation location of windings were extracted and compared each other. The SFCL with windings in the center leg of E-I core was shown to be larger magnetizing inductance compared to the one with windings in the right or left leg of E-I, which was analyzed from the hysteresis curve. In addition, larger decreased fault current right after the fault occurrence in the SFCL with windings in the center leg of E-I core was confirmed than the SFCL with windings in the right or left leg of E-I.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.529-532
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• 2003

Quench behavior of resistive superconducting fault current limiters (SFCLs) with various pattern shapes was investigated. The pattern shapes employed were meander, bi-spiral, and spiral shapes of identical line width, gap and margin. SFCLs were fabricated from YBCO thin films grown on two-inch diameter $Al_2O_3$ substrates under the same conditions. Resistance rise of current limiting elements was low at a spiral shape before the whole quench completion, which may act as a disadvantage for simultaneous quench in serial connection between current limiting elements, but the temperature tended to have similar values at higher voltages. On the other hand, bi-spiral shape was severe at insulation level between current limiting lines. When these aspects were considered, we concluded that a meander shape was appropriate to design for a resistive SFCL based on thin films except the concentration of electric field at edge areas of strip lines.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.4
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• pp.343-350
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• 2003

Using Bi$_2$Sr$_2$Ca$_2$.$_2$Cu$_3$ $O_{x}$ powders prepared by solid state reaction and spray drying method, the nucleation and growth behaviors of superconducting and second phases were investigated during isothermal heat treatment. When the spray drying power was used in contrast with solid state reaction powder, Bi$_2$Sr$_2$Ca$_2$.$_2$Cu$_3$ $O_{x}$ (2223) phase could be formed at the relatively shot time and second phases were much bigger. Quantitative analysis showed that as the heat treatment time increased, more Bi$_2$Sr$_2$Ca$_2$.$_2$Cu$_3$ $O_{x}$ (2212) changed to 2223 and the major second phase was changed from (Sr,Ca)$_{14}$Cu$_{24}$ $O_{x}$(14:24) to (Sr,Ca)$_2$Cu$_1$ $O_{x}$ (2:l). The superconducting phase formed at the relatively short time 14:24 phase. Following the Bi-free phase of 14:24 Phase, but long time was needed in places far from the 14:24 phase. Following the formation of the 2212 phase near the 14:24 phase, the 2223 phase nucleated preferentially at the interface between the 2212 and 14:24 phases. The preferential nuclcation of 2223 was explained by its structural similarity and low Interfacial energy with both the Bi-free and 2212 Phases.12 Phases.