• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 1999.02a
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• pp.1-6
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• 1999

The recent progress in the new cooling technology for superconducting systems without liquid cryogens is briefly presented. In these conduction-cooled systems, the super-conducting magnets are cooled by a direct contact with closed-cycle cryocoolers and only electricity is supplied to maintain the cryogenic temperatures. It is reported that at least 20 conduction-cooled (low Tc or high Tc) super- conducting systems have been constructed, tested, or commercially used worldwide. Some of the significant design issues are discussed in comparison with the conventional liquid-helium cooled systems.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1988.10a
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• pp.102-104
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• 1988

GdBa$_2$Cu$_3$Ox superconductors were prepared by ceramic powder compacting method. X-ray powder diffraction patterns and SEM microphotographs were taken to analyze phase and microstructure, and electrical properties were investigated by 4-point probe method. The results show that the $N_2$atmosphere enhances the formation of high Tc(critical temperature) phase, but the Tc is independent of sintering conditions.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.9
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• pp.1775-1777
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• 2009

BiSrCaCuO films were prepared on MgO single substerate at $885^{\circ}C$ by melt process. The films showed superconductivity above liquid nitrogen temperature (Tc= 96K). To investigate the effect of a melting temperature on the forming of the surface texturing, the samples were prepared under various temperature. The used powder was of high Tc phase. It is implies that the origin of the properties due to the heat treatment.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.322-325
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• 2002

In this paper, the power-linking device connecting the high-Tc super-conducting(HTS) coil to the power system in the DC reactor type three-phase high-Tc superconducting fault current limiter (SFCL) has been designed. This design was triggered from the concept that the magnetic energy could be exchanged into the electrical energy each other. Ferromagnetic material is used as the path of magnetic flux. The device mentioned above was named Magnetic Core Reactor(MCR). MCR was designed to minimize the voltage drop caused by copper loss. The current density of the conductor was 1.3 A/mm$^2$ and % voltage drop was 2%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.222-224
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• 1997

This study is about a connective method of High Tc wire for long wire. We prepared silver-sheathed BiPbSrCaCuO wires by the powder-in-tube method. Since the superconducting wires are ceramic, it is very hard to connect each other. In this study, we used a silver sleeve to contract wires and pressed them by various preasures. Then optimum preasure was 9,000 Kgf/$\textrm{cm}^2$ to get the high critical current. The higest critical current was 10A.

• Progress in Superconductivity and Cryogenics
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• v.17 no.3
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• pp.18-22
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• 2015

This paper deals with high-Tc superconducting (HTS) power charging system with GdBCO magnet, photo-voltaic (PV) controller, and solar panels to charge solar energy. When combining the HTS magnet and the solar energy charging system, additional power source is not required therefore it is possible to obtain high power efficiency. Since there is no resistance in superconducting magnet carrying DC transport current the energy losses caused by joule heating can be reduced. In this paper, the charging characteristics of HTS power charging system was simulated by using PSIM. The charging current of HTS superconducting power charging system is measured and compared with the simulation results. Using the simulation of HTS power charging system, it can be applied to the solar energy applications.

• 한국초전도학회:학술대회논문집
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• v.10
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• pp.9-14
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• 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.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.12
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• pp.640-645
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• 2006

A 22.9kV/50MVA class high temperature superconducting(HTS) power cable system was developed in Korea. For the optimization of electrical insulation design for a HTS cable, it is necessary to investigate the ac breakdown impulse breakdown and partial discharge inception stress of the liquid nitrogen/laminated polypropylene paper(LPP) composite insulation system. They were used to insulation design of the model cable for a 22.9kV class HTS power cable and the model cable was manufactured. The insulation test of the manufactured model cable was evaluated in various conditions and was satisfied standard technical specification in Korea. Base on these experimental data, the single and 3 phase HTS cable of a prototype were manufactured and verified.

• Progress in Superconductivity
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• v.9 no.2
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• pp.127-135
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• 2008

We study the effects of phonon interaction on the superconducting pairing in the high $T_c$ superconductors (HTSC). Using coupled BCS gap equations, we found that phonon interaction can induce a s-wave component to the d-wave gap, mediated by Antiferromagnetic (AFM) spin fluctuations, in the (D+iS) form. However, $T_c$ is not enhanced compared to the pure d-wave pairing without phonon interaction. On the other hand, anisotropic phonon interaction can dramatically enhance the d-wave pairing and $T_c$ itself, together with the AFM spin fluctuation interaction. This ($D_{AFM}+D_{ph}$) type pairing exhibits strongly reduced isotope coefficient despite the large enhancement of $T_c$ by phonon interaction.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.43-46
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• 2003

The dc reactor type high-Tc superconducting fault current limiter(SFCL) is composed of three parts, a power converter, a magnetic core reactor(MCR) and a dc reactor. This study concerned with the power converter of the DC reactor type high-Tc SFCL. The rectifying devices which power converter of 6.6kV/200A SFCL consists of have to endure high voltage. We propose the dual mode power converter to reduce the voltage which each rectifying device endures. In the single phase the experiment and simulation of dual mode power converter and the simulation of power converter with one bridge rectifier are performed. The current of each system with different power converter has a same tendency and the voltage which rectifying device of dual mode power converter endures is reduced in half by comparison with that of power converter with one bridge rectifier. We found dual mode power converter can be applied to SFCL.