• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.265-266
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• 2006

Superconductor is developed for applications in high-power devices such as power-transmission cables, transformers, motor and generators. In such applications, HTS tapes are subjected to various kinds of stress or strain. In the fabrication of the devices, the critical current (Ic) of the high temperature superconductor degrades due to many reasons including the tension applied by bending, twist and thermal contraction. In particular manufactured HTS cable, we need pitch angle controls. This paper is analyzed that Ic characteristics is changed pitch angle of HTS tape. These results will amount the most important basis data in HTS cable.

• Progress in Superconductivity and Cryogenics
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• v.6 no.4
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• pp.37-40
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• 2004

A 1 MV A single phase high temperature superconducting (HTS) transformer was manufactured and tested. The rated voltages of primary and secondary of the HTS transformer are 22.9 kV and 6.6 kV respectively. BSCCO-2223 HTS tape was used for HTS windings of 1 MV A HTS transformer. In order to reduce AC loss generated in the HTS winding, the type of concentric arrangement winding was adopted to a 1 MV A HTS transformer. Single HTS tape for primary windings and 4 parallel HTS tapes for secondary windings were used considering the each rated current of the HTS transformer. A core of HTS transformer was fabricated as a shell type core made of laminated silicon steel plate. And a GFRP cryostat with a room temperature bore was also manufactured. The characteristic tests of 1 MV A HTS transformer were performed such as no load test, short circuit test and several insulation tests at 65 K using sub-cooled liquid nitrogen. From the results of tests, the validity of design of HTS transformer was ascertained.

• 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.

• 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.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.203-205
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• 2003

Parallel wounded windings with BSCCO-2223 HTS tape for 1MVA HTS transformer were designed and prototype windings were fabricated in double pancake type. The parallel HTS tapes were transposed between the pancakes via non-superconducting joints because it is hard to make transpositions inside the pancake windings. The prototypes were wound using copper tape with same size as BSCCO-2223 tape, which will be used in 1MVA HTS transformer. The windings will be used for high voltage test and insulation test of the transformer Parallel HTS windings are going to be fabricated and tested for current distribution in near future.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.244-245
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• 2007

Specially, High Temperature Superconducting power-transmission cable(HTS cable), 3-phase 100m long, 22.9kV class HTS power transmission cable system have been developed by Korea Electrotechnology Research Institute (KERI) and LS cable Ltd. that is one of 21st century frontier project in Korea. This cable was installed in KEPCO(Go-chang) testing site. In case of manufacturing HTS cable, superconducting joint is very important because they need very long tapes. Therefore, this paper gives some investigation of AC Loss in joined HTS tape by using several joint methods. Finally, this paper was shown background data for the form of HTS cable joint.

• Progress in Superconductivity and Cryogenics
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• v.19 no.4
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• pp.26-30
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• 2017

The promising characteristics of 2G high-temperature superconductor (HTS) coated conductor (CC) tapes have made it possible to apply to various electrical device applications. In this study, the mechanical and electromechanical properties of Sn-Cu double layer stabilized GdBCO CC tapes have been characterized. The stress and strain tolerances of $I_c$ in GdBCO CC tapes adopting stainless steel substrate were evaluated using $I_c$-strain measurement at 77 K under both uniaxial tension and monotonic bending conditions. The results were compared to the conventional single Cu layer stabilized CC tape. As a result, the Sn-Cu double layer stabilized GdBCO CC tapes showed somehow lower or comparable electromechanical properties as compared to the Cu stabilized CC tape ones.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.10a
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• pp.131-133
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• 2003

The effect of axial strain and thermal cycling on the critical current is investigated for the Bi-2223/Ag PIT tapes. The axial strain was applied to the tapes by the U-shape sample holder. Two kinds of Bi-2223/Ag tapes with different Ag sheath are used to know the effect of sheath alloying for the tensile strain. The influence of thermal cycling between room temperature and 77 K on critical current are examined. Critical current is drastically decreased for Ag/alloy and Ag/alloy/alloy sheathed tapes at tensile strain above 0.22％ and 0.3％, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.345-348
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• 2004

For practical applications, the evaluation of reliability or endurance of HTS conductors is necessary. The mechanical properties and the critical current, $I_c$, of multifilamentary Bi-2223 superconducting tapes, externally reinforced with stainless steel foils, subjected to high cycle fatigue loading in the longitudinal direction were investigated at 77K. The S-N curves were obtained and its transport property was evaluated with the increase of repeated cycles at different stress amplitudes. The effect of the stress ratio, R, on the $I_c$ degradation behavior under fatigue loading was also examined considering the practical application situation of HTS tapes. Microstructure observation was conducted in order to understand the L degradation mechanism in fatigued Bi-2223 tapes.

• Progress in Superconductivity and Cryogenics
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• v.5 no.1
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• pp.35-39
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• 2003

A typical HTS power transmission cable has multi-layer conductor structure to increase the current capacity. The tapes of the innermost layer are wound on a round former, and adjacent tapes of another layer are separated by a thin insulating film. However, usually the current is not evenly distributed among the layers because of inductance difference of each layer, and the inductance is provided by the winding pitch of each layer's tape. Consequently n method to make the current distribution more uniform is a adjusting the tape winding pitch, hence reduce the AC loss. This paper describes a current distribution by adjusting a tape winding pitch of each layer. Also, this paper shows recommendations for future cable conductor prototypes.