• KEPCO Journal on Electric Power and Energy
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• 제5권4호
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• pp.343-347
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• 2019

When referring to weight, volume, and efficiency, a SuperConducting Synchronous Generator (SCSG) is definitely superior to conventional generators as a large-scale wind power generation system. The SCSG is connected to a full power converter that transmits the energy from the SCSG to the power grid. To reduce the current stress and system cost, the SCSG which has nine-phase armature windings with three converters is used. This paper deals with a comparative analysis of 10 MW superconducting wind power generators with three-phase and nine-phase armature windings. The stator windings of SCSGs are of various types. Using the finite element method, SCSGs are analyzed and compared in terms of the weight and volume of SCSGs, the total length of the superconducting wire, harmonics, torque performance, and efficiency. The analyzed results will be effectively utilized to design large-scale superconducting generators for wind power generation systems.

• Progress in Superconductivity
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• 제4권2호
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• pp.184-188
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• 2003

Voltage-current characteristics of High Temperature Superconductor(HTS) tapes after applying the current beyond their critical current was investigated. When over-current is applied, the current begins to flow through the metal sheath instead of superconductor. The HTS tapes quenched were analyzed using V-I curve with various magnitudes of current. Two kinds of tapes were compared with each other to examine the influence of critical current on quench development. As a result, it was found that the resistance of superconductors and joule heat due to the over-current affect current distribution in HTS tapes. Critical current of HTS tapes was considered as a main factor deciding over-current characteristics.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1992년도 추계학술발표강연 및 논문개요집
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• pp.17-17
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• 1992

The ceramic high transition temperature superconducting materials present many interesting characteristics that will be analysed from two points of view: physical behavior, and chemical aspects. From the first point of view, these materials display an enormous variety of different physical properties. At low doping levels the normal state shows antiferromagnetism and insulating behavior. At intermediate doping levels, an anomalous metallic state appears and, the optimum Tc in the superconducting state is generated. With increasing doping a normal metallic state develops and superconductivity starts to disappear. Many of the physical phenomena that describe the overall behavior when doping levels are changed will be discussed. From the poing of view of the chemical aspects. we well discuss some of the problems involved in the methods of preparation with particular emphasis on defects, crystal structures, critical currrents, and applications in technology.

• 한국초전도ㆍ저온공학회논문지
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• 제7권1호
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• pp.25-31
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• 2005

Since the discovery of the high temperature superconductors many researches have been performed for the practical applications of superconductivity technologies in various fields. As results, significant progress has been achieved. Especially, Superconducting Fault Current Limiter (SFCL) offers an attractive means In limit fault current in power systems. HTS resistive type SFCL is based on the ultra fast transition from the superconducting (non resistive) state to the normal (resistive) state by overstepping the critical current density, In this study, the simulation method of resistive type superconducting fault current limiter using EMTDC is proposed and the developed EMTDC model of SFCL is applied to the modeled power network using the Parameters of real system.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.343.2-343
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• 2002

Squeeze film dampers(SFDs) are designed and analyzed for radial superconducting bearings. The designed SFDs are mounted on the superconductors submerged in liquid nitrogen such that the dampers should supply additional damping to the relatively underdamped superconducting bearing support. Basic theory of SFD with superconducting bearing are introduced. Rotordynamic simulations are provided to support the feasibility of the superconducting magnetic bearings mounted on SFDs for a horizontal flywheel energy storage system.

• Progress in Superconductivity
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• 제3권2호
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• pp.168-171
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• 2002

We have demonstrated ramp-edge Josephson junctions using high temperature superconductors without depositing artificial barriers. We fabricated a surface barrier formed naturally during an ion beam etching process and the annealing under the oxygen atmosphere. The experimental results imply that the barrier natures such as the resistivity are varied by the annealing conditions and the ion milling conditions including the beam voltages. Thus, the ann eating and etching conditions should be optimized to obtain excellent junction properties. In optimizing the fabricating factors, the interface-controlled junctions showed resistively shunted junctions like current-voltage characteristics and an excellent uniformity. These junctions exhibited a spread ($1\sigma$) of $I_{c}$ is 10% fur chips containing 7 junctions at 50K.K.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 A
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• pp.412-414
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• 2003

Since the discovery of the high-temperature superconductors, many researches have been performed for the practical applications of superconductivity technologies in various fields. As results, significant progress has been achieved. Especially, Superconducting Fault Current Limiter (SFCL) offers an attractive means to limit fault current in power systems. In order to verify the effectiveness of the SFCL, in this paper, the analysis of fault current and voltage stability assessment in a distribution system are studied using the EMTDC based simulation method in which a novel component for a resistive type of SFCL is presented. Through the simulation, the most suitable SFCL's application point is selected and the assessment method for the parameters of the SFCL is also recommended.

• 한국초전도ㆍ저온공학회논문지
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• 제25권4호
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• pp.40-44
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• 2023

For high-temperature superconducting power applications that need large current capacity, a large current conductor manufactured using multiple superconducting tape is required. Conductors being studied for large currents capacity such as CORC, TSTC, and RACC have advantages and disadvantages, and in order to use these conductors in coil form and apply them to AC power devices, research on magnetization loss occurring in superconductors due to external magnetic fields is essential. To accurately measure magnetization loss in a conductor that is twisted by stacking straight conductors like TSTC, the correlation between the measuring system and the shape of the sample must be clearly known to accurately measure the loss. In this paper, we will confirm the difference in magnetization loss measurement values according to the correlation between the length of the pickup coil and the twist pitch of the sample in CORC and TSTC shapes, and review considerations for accurate magnetization loss measurement from the results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
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• pp.115-116
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• 2006

Since the discovery of the high-temperature superconductors, many researches have been performed for the practical applications of superconductivity technologies in various fields. As results, significant progress has been achieved. Especially, Superconducting Fault Current Limiter (SFCL) offers an attractive means to limit fault current in power systems. The SFCLS, in contrast to current limiting reactors or high impedance transformers, are capable of limiting short circuit currents without adding considerable voltage drop and energy loss to power systems during normal operation. Under fault conditions, a resistance is automatically inserted into the power grid to limit the peak short-circuit current by transition from the superconducting state to the normal state, the quench. The advantages, like fail safe operation and quick recovery, make SFCL very attractive, especially for rapidly growing power systems with higher short-circuit capacities. In order to verify the effectiveness of the SFCL, in this paper, the analysis of fault current and voltage stability assessment in a sample distribution system and a transmission system are performed by the PSCAD/EMTDC based simulation method. Through the simulation, the advantage of SFCL application is shown, and the effective parameters of the SFCL are also recommended for both distribution and transmission systems. A resistive type component of SFCL is adopted in the analysis. The simulation results demonstrate not only the effectiveness of the proposed simulation scheme but also SFCL parameter assessment technique.

• 한국표면공학회지
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• 제29권5호
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• pp.415-423
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• 1996

Thin film technologies for fabricating SQUIDs involve etching and deposition procedures with the proper substrate materials and $YBa_2Cu_3O_{7-d}$ (YBCO) as the high $T_c$ superconductor. YBCO were prepared on various substrates of MgO, $SrTiO_3$, and $LaAlO_3$ by using off-axis magnetron sputtering methods and annealing in-situ. The parameters of film fabrication processes had been optimized to yield good quality films in terms of the critical temperature $T_c$ and the critical current density $J_c$. The optimized processes yielded $T_C$>90K along with $J_c$>$10_6A$$extrm{cm}^2$ at 77K and>$2\times10_7A/Cm^2$ at 5K. We fabricated step-edge type dc-SQUIDs and directly coupled magnetometers, producing step edges on MgO(100) substrates by etching with Ar-ion beam, depositing YBCO material on them, then patterning them by using ion-milling technique. Circuitizing washer-shape SQUIDs to possess a pair of step-edge junctions of 2-5$\mu$ line width with a high angle>$50^{\circ}C$ , we examined their I-V characteristics thoroughly and Shapiro steps clearly as we irradiate microwaves of 8-20 GHz frequency.