• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.10a
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• pp.185-189
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• 2003

The purpose of this study is to obtain the optimal operating condition of conduction cooled taper shape high-temperature superconductor (HTS) current lead operated in current sharing mode. In our previous study, we discovered that the optimal operating condition of constant cross-section area HTS current lead is in the current sharing state, and in optimal condition, the temperature gradient at warm end is not zero. The analysis result of taper HTS current lead is quiet similar to the constant area HTS current lead. The minimum dissipation of taper HTS current lead is not influenced by taper angle, however the optimal operation condition is varied with taper angle.

• Progress in Superconductivity and Cryogenics
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• v.3 no.1
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• pp.35-39
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• 2001

The optimum cross-sectional area profile of gas-cooled high-temperature superconductor(HTS) current lead is analyzed to have minimum helium boil-off rate. The conventional constant area HTS lead has much higher helium consumption than the optimum HTS lead considered in this study. The optimum HTS lead has variable cross-sectional area to have constant satiety factor. An analytical formula of optimum shape of lead and temperature profile are obtained. For multi-stacking HTS current leads, the optimum tape lengths and minimum heat dissipation rate are also formulated. The developed formulations are applied to the Bi-2223 material, and the differences between constant area, constant safety-factor, and multi-stacking current leads are discussed.

• 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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• 2001.11b
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• pp.131-136
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• 2001

In this paper, a high-temperature superconductor(HTS) current lead operating in current sharing mode is described. The minimum heat dissipation and the optimum safety factor(cross-sectional area) is obtained analytically for partial current sharing HTS leads. It is assumed that the current lead is in conduction cooled state, and the sheath material is the alloy of silver and gold. The reduced cross-sectional area results partial current sharing state, and consequently reduces conduction heat transfer, but the Joule heat generation is increased. The optimized HTS current lead is different from the conventional copper leads. In the copper leads, the minimum heat dissipation is obtained for the zero gradient of temperature at warm end. However, the temperature gradient at warm end is not zero when the HTS lead operates at minimum dissipation state.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.10a
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• pp.7-9
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• 2003

A 3MJ class SMES was fabricated last year. And 1000A class current part for the SMES also was designed, fabricated and tested. The current lead was made of metal part(brass) and HTS lead Part. The lead is located in vacuum vessel and cooled down to belows the HTS lead's operating temperature. We made three types of current lead part and tested their performance. In this paper, the basic and conceptual type of current lead will be introduced. The lead was expected to have 1000A current capacity. But the test results was only 480A. After this test, based on the results we revised the shape of the lead and improved the connectivity between cryocooler and lead. In this paper, the design procedure and the results of performance test will be introduced.

• 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.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2001.02a
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• pp.84-88
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• 2001

The optimum cross-sectional area Profile of gas-cooled high-temperature superconductor (HTS) current lead is analyzed to have minimum helium boil-off rate. The conventional constant area HTS lead has much higher helium consumption than the optimum HTS lead considered in this study. The optimum HTS lead has variable cross-sectional area to have constant safety factor. An analytical formula of optimum shape of lead and temperature profile are obtained. For multi-step HTS current leads, the optimum tape lengths and minimum heat dissipation rate are also formulated. The developed formulations are applied to the Bi-2223 material, and the differences between constant area, constant safety-factor, and multi-step current leads are discussed.

• Progress in Superconductivity and Cryogenics
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• v.2 no.2
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• pp.15-19
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• 2000

The stability of variable cross-sectional area HTS current lead is considered. The cross-sectional area is varied to have a constant safety factor which is defined as the ratio of operating current and critical current of superconductor. As the constant area HTS lead, the variable cross-sectional area HTS lead also has three steady states above the bifurcation point and only one steady state below the bifurcation point. The temperature profiles and current sharing ratios for each steady state are calculated. The heat dissipation into cryogenic system for super-conducting, intermediate, and upper states are compared. For Bi-2333 sheathed with silver-gold alloy 2m length of current lead, and the maximum temperature of upper state seems to be burn-out free below 5m length.

• Progress in Superconductivity and Cryogenics
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• v.16 no.2
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• pp.54-58
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• 2014

High-temperature superconducting (HTS) rotating machines always require an electric current of from several hundreds to several thousand amperes to be led from outside into cold region of the field coil. Heat losses through the current leads then assume tremendous importance. Consequently, it is necessary to acquire optimal design for the leads which would achieve minimum heat loss during operation of machines for a given electrical current. In this paper, conduction cooled current lead type of 10 MW-Class HTS rotating machine will be chosen, a conceptual design will be discussed and performed relied on the least heat lost estimation between conventional metal lead and partially HTS lead. In addition, steady-state thermal characteristic of each one also is considered and illustrated.

• 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.