• Progress in Superconductivity and Cryogenics
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• v.14 no.3
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• pp.5-8
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• 2012

Superconducting windings of synchronous machine have to be operated in below the critical temperature, critical current density and critical magnetic field. If one of these characteristics does not satisfied, then the quench occurred in superconducting winding. Especially the armature current dramatically increased as the superconducting generator is short-circuited at the rated load condition and magnetic field in field winding increased due to the armature current. Therefore, damper is required to reduce the magnetic field of field winding which increases reliability of the superconducting generator. Damper dimension can be decided by time constant[1-2]. In this paper the basic model is high-power and low-speed superconducting generator. Damper time constant was calculated from the changed damper thickness and material. Magnetic flux of field coil at the basic model and changed damper time constant model is analyzed.

• Journal of the Korean Ceramic Society
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• v.25 no.2
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• pp.154-160
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• 1988

Almost single phase of Y1Ba2Cu3Ox, which exhibits the onset of superconducting transition at 90K, has been prepared via a conventional ceramic processing route followed by an anneal for a period of 10 hours at 45$0^{\circ}C$ in an atmosphere of 100% O2. The mean value for the oxygen content has been determined as x=6.85$\pm$0.02 by an iodometric titration technique. X-ray photoemission spectra are found to be consistent with a mixture of the d8(Cu3+) and d9(Cu2+) as the ground state and reveals that the local concentration of Cu3+ decreases with depth from the surface where x corresponds to 7.0. This is explained as being associated with the intercalation of oxygen during cooling from the annealing temperature.

• Journal of the Korean Ceramic Society
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• v.26 no.2
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• pp.267-275
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• 1989

YBa2Cu3O7-x oxide superconductors were fabricated by sintering and hotisostatic pressing (HIP), and their microstructures and properties were compared with each other. Thougha part of the second phase was observed along grain boundaries, their structures were consisted of single (123) phase and they had many porosities. But, porosities were remakably reduced by Hiping and the densification was brought about. The structure of (123) compound also showed a number of twins, which are typical of high Tc superconductors. The on-set temperature of YBa2Cu3O7-x compound sintered at 96$0^{\circ}C$ in oxygen and hipped at 88$0^{\circ}C$ was highest, but that shwoed 0 resistance at 87$^{\circ}$K, which is a little lower than the compound sintered at 96$0^{\circ}C$. HIP treatment also increased the critical current density of as-sintered compound. However, its value was low, which may be ascribed to the many pores of starting-sintered compact and partially to the second phase along grain boundaries.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.421-423
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• 2003

To prevent fault effect in supply of electric power distribution system and plan stable operation of electric power system, must control magnitude of fault current. Although there are various kinds of method to solvethis, approached from super conductivity Fault Current Limiter application viewpoint among them. High Temperature Superconductor-Fault Current Limiter (HTS-FCL) development is progressing according to HTS technology development, and system application is tried. For actual system application of such super conductivity FCL, so that can reflect special quality of actuality supply of electric power distribution system just as it is in this treatise supply of electric power system by two modelling do. Also, by simulation of HTS-FCL action and protection coordination with another equipment appliances, verified the effectiveness in supply of electric power system applying itself super conductivity FCL EMTDC dynamic characteristic model that is develope.

• KIEE International Transactions on Power Engineering
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• v.4A no.2
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• pp.69-72
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• 2004

Nowadays, one of the serious problems in the KEPCO system is a much higher fault current than the SCC (Short Circuit Capacity) of the circuit breaker. Since superconductivity technology has become more developed, the HTS-FCL (High Temperature Superconductor-Fault Current Limiter) may become an attractive alternative to solving the fault current problem. In order to achieve the best performance, the parameters of HTS-FCL should be designed optimally. Under this setting, this paper presents the optimal design method of parameters for resistive type HTS-FCL using the Monte Carlo technique.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.41-44
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• 1998

Dual mode resonators were fabricated using high temperature superconductor. The deposited material was $Y_1Ba_2Cu_3O_{7-x}$(YBCO) on MgO(100) substrate using pulsed laser deposition. Dual mode resonators were patterned by standard photolithography process and wet etching. At the back-side of the substrate, the ground plane with the metal layer of Ti and Ag was fabricated. The transition temperatures of YBCO films were 85-88 K, and network analyzer was used for testing the performance of the resonators. The input/output feedline angles of each resonator were $60^{\circ}$and $100^{\circ}$. The resonant frequency of resonators was 10 GHz. In this paper, dual mode resonator was fabricated for the application of satellite communication.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.10a
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• pp.205-208
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• 2003

Maximum short circuit current of modern power system is becoming so large that the current should transmission capability. Although there are various kinds of method to solve this, approached from super conductivity Fault Current Limiter application viewpoint among them. High Temperature Superconductor-Fault Current Limiter (HTS-FCL) development is progressing according to HTS technology development, and system application is tried. For actual system application of such super conductivity FCL, an efficient method to find FCL locations suitable for reduction of short circuit currents of more than one fault location is developed.

• Korean Journal of Materials Research
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• v.6 no.6
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• pp.555-560
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• 1996

The vibrational behavior and the molecular dynamics of the high Tc superconductor Ba0.6K0.4BiO3 have been studied experimentally and by atomistic computer simulation methods. For Ba0.6K0.4BiO3, the vibrational spectrum is dominated by oxygen ion modes from 150cm-1 to 820cm-1 including infrared absorption bands at 330, 480, 640 and 830cm-1including infrared absorption bands at 330, 480, 640 and 830cm-1at room temperature. Band assignments are discussed in relation to those bands predicted by simulations, and the infrared and Raman measurements reported in the literature.

• Korean Journal of Materials Research
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• v.7 no.5
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• pp.431-433
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• 1997

We investigated a double ring resonator(DRR)device to improve the resonating Q value of a superconductor resonator. To make a DRR device, we made a large area YBCO film on a MgO substrate by pulsed laser deposition(PLD). Thetransition temperature was 88 K and the film was uniformly deposited. We also deposited 500$\AA$SrTiO$_{3}$on the YBCO thin film to protect the superconducting properties from degradation. The loaded Q value was measured as 50000 from simulation and as 2000 from experiment near 10GHz at 77K.

• Progress in Superconductivity and Cryogenics
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• v.7 no.3
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• pp.1-4
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• 2005

As high temperature superconductor applications became a reality due to increase in coated conductor performance, it is important to understand their stability behavior to design safe electrical power systems. Coated conductors can be stabilized with different metals and alloys for different types of application, to yield excellent electrical, thermal and mechanical performance. We have experimentally studied the dependence of quench and recovery characteristics of stainless steel stabilized coated conductors on the amplitude of current and duration time. Stability test of 3cm long sample were performed in a liquid nitrogen bath cooling condition by applying a short period over current pulses for 50 and 100ms, with amplitude up to ~6 times the critical current. The transport current that flows before and after the current pulse was fixed at about ~80-85% critical current. We analyzed the quench and recovery phenomena of the test sample using the current voltage characteristic.