• Progress in Superconductivity and Cryogenics
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• v.12 no.1
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• pp.32-36
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• 2010

Superconducting current leads are indispensible for reducing power loss when subjecting current into superconducting magnets. HTS(High-Tc superconducting) current leads are divided into two types; one is bulk type and the other is tape type. In this paper, conceptual design on the HTS current leads which adopts tape type for nuclear fusion magnets is carried out using magnetic field analysis and thermal analysis. When large current flows through superconducting current leads, strong self magnetic field is generated and applied to the superconducting tapes. This phenomenon leads to the critical current decrease of the superconducting tape. Therefore, we analyzed magnetic field distribution of current leads and found the proper arrangement with respect to the various HTS tapes. In addition to the magnetic field analysis, heat leak through the current leads was also calculated to know which HTS tape is superior than others in thermal aspect. Magnetical field analysis and calculation of heat leak are performed to design 2 kA class HTS current leads.

• Progress in Superconductivity and Cryogenics
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• v.4 no.1
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• pp.66-72
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• 2002

This paper describes numerical modeling for thermal characteristic of vapor-cooled current leads under pulse operation. The transient thermal analysis considers the temperature difference between a helium gas (low and a copper lead and temperature dependent properties of helium gas, copper and stainless steel. This numerical modeling was compensated and validated by an experiment with commercially available 100 A vapor-cooled current leads. A proper overloading factor was suggested for the current leads under pulse operation through this modeling, which can significantly reduce heat input to a cryostat.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.50-55
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• 2002

The transient numerical analysis was performed for vapor cooled current leads. The present numerical modeling considered that there is temperature difference between the copper lead and the helium vapor flow. This numerical modeling was compensated and validated by the experiment with commercially available 100 A current leads. The numerical modeling in this paper described thermal characteristics of overloaded current leads more accurately than the conventional steady state analysis. Proper design of overloaded current leads was suggested by indicating the appropriate overloading factor in the pulse mode operation.

• Progress in Superconductivity and Cryogenics
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• v.3 no.2
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• pp.44-48
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• 2001

SMES consists of Superconducting magnet, a power converter, a cryostat and HTS current leads The prototype cryostat with HTS current leads and refrigerators was designed and manufactured for developing micro SMES. The temperature rise under dc current in HTS current leads was measured. The performances of helium boil-off and mechanical stress were evaluated during transfer and vibration tests. The results will be used to develope the micro-SMES system.

• International Journal of Air-Conditioning and Refrigeration
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• v.14 no.3
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• pp.94-101
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• 2006

A theoretical investigation to find thermodynamically optimum design conditions of conduction-cooled Peltier current leads is performed. A Peltier current lead (PCL) is composed of a thermoelectric element (TE), a metallic lead and a high temperature superconductor (HTS) lead in the order of decreasing temperature. Mathematical expressions for the minimum heat flow per unit current crossing the TE-metal interface and the minimum heat flow per unit current from the metal lead to the joint of the metal and the HTS leads are obtained. It is shown that the temperature at the TE -metal interface possesses a unique optimal value that minimizes the heat flow to the joint and that this optimal value depends on the material properties of the TE and the metallic lead but not the joint temperature nor electric current. It is also shown that there exists a unique optimal value for the joint temperature between the metal and the HTS leads that minimizes the sum of the power dissipated by ohmic heating in the current leads and the refrigerator power consumed to cool the lead, for a given length of the HTS.

• Progress in Superconductivity and Cryogenics
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• v.1 no.2
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• pp.37-42
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• 1999

The stability of high-temperature superconducting current leads for cryogenic devices are investigated. By assuming full transition from superconducting state to normal state at a transition temperature, the HTS current at a transition temperature, the HTS current lead shows bifurcation phenomenon. There is a bifurcation shape-factor, HTS leads have three steady state. Below the bifurcation shape-factor, the superconducting current lead is unconditionally stable, because there exists only one steady-factor HTS current lead is conditionally stable depending on the shape and intensity of disturbance.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.379-384
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• 2000

High-Tc superconducting current leads with multi-step and continually varied cross-sectional area are studied to reduce heat leak into cryostat and material use. Assuming conduction-cooled lead the cross-sectional area is reduced along the heat flow direction according to the increase of critical current density which increases with decreasing temperature. In this study, we also analyze the multi-step cross-sectional area High-Tc current leads. The multi-st데 current leads changes the cross-sectional area to have constant safety-factor at changed section. The heat leak into cryostat, total voume, safety-factor and the temperature profiles are compared to those of the constant safety-factor current leads. The developed methods are applied to the Bi-2223 superconductor sheathed with Ag-Au alloy.

• Progress in Superconductivity and Cryogenics
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• v.9 no.3
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• pp.62-66
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• 2007

Electromagnetic forces (Attractive and repulsive force), interacting between current leads show different tendency according to the arrangement of current leads on the top flange of the cryostat and the distance of each lead. Especially in case of high-current electric power devices or high-field magnets, optimal arrangement of current leads becomes one of the safety issues to be considered for minimizing the electromagnetic for ce acting on them. In this paper, we suggest an optimal arrangement method with three pairs of current leads for a 24kV class 650A superconducting fault current limiter (SFCL) system which has a probability of unpredicted fault currents(i.e, 20kA).

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2000.02a
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• pp.22-25
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• 2000

To improve the performance of high temperature superconducting current leads, variable cross-sectional area is considered. The cross-sectional area is varied as a function of current density to fix the safety factor along lead length. New integration method is devised to find optimum cross-sectional area distribution. New design of current lead has low heat leak into cryostat and less material than constant cross-sectional area leads. Conduction cooled lead is considered. The developed method is applied to Bi2223 current leads sheathed Ag-Au alloy.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.8
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• pp.764-771
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• 2005

A theoretical investigation for optimization of conduction-cooled Peltier current leads is undertaken. A Pottier current lead (PCL) is composed of a thermoelectric element (TE), a metallic lead and a high Tc superconductor (HTS) lead in the order of decreasing thermoelectric tempera ture. Mathematical expression for the minimum heat flow per unit current crossing the TE metal interface and that flowing from the metal lead to the joint of the metal and the HTS leads are obtained. It is shown that the temperature at the TE-metal interface possesses a unique optimal value that minimizes the heat flow to the joint and that this optimal value depends on the material properties of the 73 and the metallic lead but not the joint temperature nor electric current. It is also shown that there exists a unique optimal value for the joint temperature between the metal and the HTS leads that minimizes the sum of the power dissipated by ohmic heating in current leads and the refrigerator power consumed to cool the lead, for a given length of the HTS.