• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.3
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• pp.269-274
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• 2002

(Sm/Y)-Ba-Cu-O system high Tc composite superconductors with/without $CeO_2$ additive were directionally grown by zone-melting process, haying large temperature gradient, In air atmosphere. Cylindrical green rods of $({Sm/y})_{1.8}Ba_{2.4}Cu_{3.4}O_x$ [(Sm/Y)1.8] composite oxides by cold isostatic pressing(CIP) method using rubber mold were fabricated. The microstructure and superconducting properties were investigated by XRD, SEM, TEM and SQUID magnetometer. The size of nonsuperconducting $({Sm/y})_2BaCuO_5$ inclusions of the melt-textured (Sm/Y)1.8 sample with CeO$_2$ additive were remarkably reduced and uniformly distributed within the superconducting (Sm/Y)1.8 matrix. Both samples, with/without $CeO_2$ additive, showed an onset Tc $\geq$ 90 K and sharp superconducting transition. The critical current density Jc value of the $CeO_2$ addictive were $1{\times}10^5A/\textrm{cm}^2$ in 77 K, 0 Tesla.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.4
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• pp.363-369
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• 2005

we compared the operating characteristics between flux-lock type and resistive type superconducting fault current limiters(SFCLs). Flux-lock type SFCL consists of two coils, which are wound in parallel each other through an iron core, and a high-Tc superconducting(HTSC) element is connected with coil 2 in series. The the flux-lock type SFCL can be divided into the subtractive polarity winding and the additive polarity winding operations according to the winding directions between the coil 1 and coil 2. It was confirmed from experiments that flux-lock type SFCL could improve both the quench characteristics and the transport capacity compared to the resistive type SFCL, which means, the independent operation of HTSC element.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.474-477
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• 2002

We performed a continuous heat treatment experiment for long Si$_2$Sr$_2$CaCuO$_{x}$ (Bi2212) superconductor tapes on copper substrates. A precursor that contains a mixture of Bi$_2$O$_3$, SrCO$_3$, and CaCO$_3$ powders was prepared and screen-printed on Cu tapes. The screen- printed tapes were thermally treated by consecutive processes with various temperature settings using an air-filled tube furnace. The diffraction patterns and the microstructures of the high temperature superconductor thick films were analyzed by X-ray diffractometry (XRD) and optical Microscopy respectively, and the critical temperatures of the superconducting thick films were measured. The critical temperatures of the superconducting films were measured to be about 77K, and the films'crystallographic c-axes were confirmed to be normal to the film surfaces by XRD and morphology observation. We also observed that the thick superconducting layer is formed and aligned on the copper substrate via partial melted state that consists of a liquid phase and a secondary phase.e.

• Transactions on Electrical and Electronic Materials
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• v.6 no.6
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• pp.294-300
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• 2005

According to the trend for electric power equipment of high capacity and reduction of its size, the needs for the new high performance electric equipments become more and more important. On of the possible solution is high temperature superconducting (HTS) power application. Following the successful development of practical HTS wires, there have been renewed activities in developing superconducting power equipment. HTS equipments have to be operated in a coolant such as liquid nitrogen ($LN_2$) or cooled by conduction-cooling method such as using Gifford-McMahon (G-M) cryocooler to maintain the temperature below critical level. In this paper, the dielectric strength of some insulating materials, such as unfilled epoxy, filled epoxy, and polyimide in $LN_2$ was analyzed. Epoxy is a good insulating material but fragile at cryogenic temperature. The filled epoxy composite not only compensates for this fragile property but enhances its dielectric strength.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.288-288
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• 2008

The flux-coupling type superconducting fault current limiter(SFCL) is composed of a series transformer and superconducting unit of the YBCO thin films. The primary and secondary coils in the transformer were wound in series each other through an iron core and the YBCO thin film 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 thin films was generated and the fault current was limited by the SFCL. In this paper, we investigated the fault current limiting characteristics according to fault current level in the flux-coupling type SFCL. The experiment results that the fault current limiting characteristics was improved according to increase of the fault current level.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.289-289
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• 2008

We investigated the operational characteristics of the separated three-phase flux-lock type superconducting fault current limiter (SFCL). The single-phase lock type SFCL consist of two coils, which are wound in parallel through an iron core. The high-$T_c$ superconducting(HSTC) thin film connected in series with secondary coil. The separated three-phase flux-lock type SFCL consist of three single-phase flux-lock type SFCL. In a normal condition, the SFCL is not operate. When a fault occurs, the current of a HSTC thin film exceeds its critical current by fault current, the resistance of the HSTC thin film generated. Therefore fault current was limited by SFCL. The separated three-phase flux-lock type SFCL are operated in fault condition such as the the single line-to-ground fault, the double line-to-ground fault and the triple line-to-ground fault. The experimental results, the SFCL operational characteristics was dependent on fault condition.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.290-291
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• 2008

Recently High Temperature Superconductor(HTS) Tape is limelight of the applied superconducting machines. Mainly used superconducting tape are BSCCO tape and YBCO coated tape. These superconducting tape are applied such as SMES, superconducting generator and MAGLEV. Actually superconductor tape's experimental gauge is short. For this reason, experiment was conducted. Firstly length of 50cm BSCCO, YBCO Coated conductor@Cu and YBCO coated conductor@sus are prepared. and flow the over-current. Secondly, BSCCO and Coated conductor connected with lenth of 25cm and flow the over-current. Coupled line of HTS tape was compared with single line of HTS tape and these overcurrent characteristics was investigated.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.3
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• pp.231-237
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• 2003

RE(Nd, Sm) elements doped (RE/Y)$_{1.8}$B $a_{2.4}$C $u_{3.4}$$O_{7-x}$ [(RE/Y)1.8] high $T_{c}$ superconductors were directionally grown by Top Seed Melt Growth(TSMG) process in air atmosphere. The (001)melt-textured N $d_{1.8}$B $a_{2.4}$C $u_{3.4}$ $O_{7-X}$(Nd1.8) seed crystals were used for achieving the c-axis alignment large grains perpendicular to surface of the samples. The (RE/Y)1.8 SEM micrographs of the melt-textured (RE/Y)1.8 samples revealed that the nonsuperconducting (RE/Y)211 inclusions are uniformly distributed in the superconducting (RE/Y)123 matrix except the region very close to the Nd seed crystal. The microstructure and superconducting properties were investigated by XRD, SEM, TEM and SQUID magnetometer. The Melt-textured (RE/Y)1.8 samples showed an onset $T_{c}$=91K and sharp superconducting transition. Also, the magnetization value of the (RE/Y)1.8 samples were compared with those of Y1.8 sample at 77 K. 77 K. 77 K. 77 K.K.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.4
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• pp.336-342
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• 2003

(Sm/Y)$_{1.8}$B $a_{2.4}$C $u_{3.4}$$O_{7-x}$ [(Sm/Y)1.8] high $T_{c}$ superconductors were directionally grown by Rod-type Seed Melt Growth(RSMG) process in air atmosphere. The sintered polycrystalline N $d_{1.8}$B $a_{2.4}$C $u_{3.4}$$O_{7-x}$(Nd1.8) of rod-type seed crystal grown by extrusion mold process were used for achieving the ab-plane alignment haying large grains perpendicular to the center of (Sm/Y)1.8 samples. The observations using TEM micrographs of the melt-textured (Sm/Y)1.8 samples revealed that the nonsuperconducting (Sm/Y)211 inclusions are uniformly distributed in the superconducting (Sm/Y)123 matrix. The microstructure and superconducting properties were investigated by XRD, TEM and SQUID magnetometer. The RSMG (Sm/Y)1.8 samples showed an onset $T_{c}$ $\geq$ 90 K and sharp superconducting transition.nsition.ion.nsition.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.19-22
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• 2003

For use in constructing highly sensitive thermal detectors, the present authors have been studying the preparation of Superconducting Flux Flow Sensor(SFFS). In this research, SFFS with five channel ($5{\mu}m$/1channel) has been fabricated based on the flux flow using high temperature superconducting thin films by the ICP etching technique. We have designed a bolometer based on the temperature dependence of the kinetic inductance of a superconducting flux flow thin film. In this paper examines the fabrications and flux flow resistance and thermometer responses of the highly sensitive sensor constructed of a thin YBCO film. It is also suggested that they will be applicable to a new type of flux flow sensor.