• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.810-813
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• 2000

In this study, we fabricated Bi-2223/Ag high temperature superconducting tapes using PIT (Powder-In-Tube) process to apply the superconducting magnet, cable and etc. It's inevitable to deform the superconducting tapes with axial strain for application. Therefore, for the characterization of the strain sensitivity of the superconducting properties, the degradation of Bi-2223/Ag tapes due to axial strain were investigated by measuring the critical current as a function of applied tension strain and external magnetic field. The critical current of Bi-2223/Ag tapes were decreased slightly up to 0.3∼0.4% applied strain but, drastically decreased more than these strains. Superconducting filament cores consisted of brittle ceramic fibers were broken easily by the large strain and current path were decreased simultaneously.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.765-767
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• 1992

A superconducting multistranded cable is used to realize high current capacity for AC use. The critical current value of the cable to be less than the simple summation of individual critical current value of each strand. The causes for such a degradation of the critical current value have not been revealed. This paper investigates the current distribution in multistrands before and after their quenching by using 7-strand superconducting cable. The following experimental results are derived. (1)The quenching is initiated at one strand in the cable, (2)The current in the quenched strand is transferred into the other strands, (3) An avalanche of quenching is induced among the strands, (4)The central strand is quenched finally among the strands.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.1081-1083
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• 1993

A superconducting multistranded cable is used to realize high current capacity for AC use. The critical current value of the cable to be less than the simple summation of individual critical current value of each strand. The causes for such a degradation of the critical current value have not been revealed. This paper investigates the current distribution in multistrands before and after their quenching by using $7{\times}7$-strand superconducting cable.

• Progress in Superconductivity and Cryogenics
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• v.6 no.1
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• pp.6-11
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• 2004

The influences of mixed strain mode of bending-tension on the critical current. Ic in externally reinforced Bi-2223 tapes and their interaction were investigated in this study. A test fixture which providing a mixed deformation mode of bending-tension to HTS tapes has been newly devised. When the total strain induced in the tape in the mixed strain mode was expressed by the superposition of the bending and tensile strains the irreversible strain for the critical current degradation of Bi-2223 tapes increased, as compared with the simple bending mode case. The $I_c$ degradation at the region exceeding the irreversible strain showed a medium between the simple bending case and the simple tension case. As the initial bending strain imparted increased , namely as the diameter of mandrel adopted decreased. the apparent irreversible strain in Bi-2223 tapes increased . but the increment became smaller As a result. it can be found that the tension to be applied to bent Bi-2223 tapes during cabling should be smaller. as the mandrel diameter becomes smaller.

• Progress in Superconductivity and Cryogenics
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• v.15 no.2
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• pp.24-28
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• 2013

In this study, the homogeneity of critical current, $I_c$, along the lengthwise direction in the coated conductor (CC) tape under uniaxial tension was investigated using a multiple voltage tap configuration. Initially, a gradual and homogeneous $I_c$ degradation occurred in all subsections of the tape up to a certain strain value. This was followed by an abrupt $I_c$ degradation in some subsections, which caused scattering in $I_c$ values along the length with increasing tension strain. The $I_c$ degradation behaviour was also explained through n-value as well as microstructure analyses. Subsections showed $I_c$ scattering corresponding to damaged areas of the CC tape revealed that transverse cracks were distributed throughout the gauge length. This homogeneous $I_c$ degradation behaviour under tension is similar with the case under torsion strain but different with the case under hard bending which were previously reported. This behaviour is also different with the case using Bi-2223 HTS tapes under tension strain.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.831-834
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• 2002

Several companies in the world are marketing superconducting wires, films and bulks. High-Tc superconducting systems using these superconductors are begun to commercialize. For the successful realization or commercialization of superconducting system used Bi-2223 wires, the database on the degradation of critical current is essentially needed. In this paper, the electrical degradation of a Bi-2223 wires is measured. The electrical degradation rate was measured after the certain time of continuous current transportation. Specimens have the length of 190cm and double-pancakes coil have the length of 10m were tested. Tested Bi-2223 wires are commercialized product has 115A of Ic. When the transportation current was 95% of Ie, the degradation of Ic was appeared after 5 hours of transportation time. When the transferred current is enough larger than Ic, Bi-2223 double pancake is damaged seriously.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.573-576
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• 2003

HTS superconducting tapes are now commercially available for practical applications such as magnets and cables. Since superconductors in such applications are subjected to high mechanical loads that can significantly degrade the superconducting properties, mechanical properties and the strain tolerance known as the strain effect on superconducting properties are needed to be estimated for developing superconducting devices. Influences of loading mode on the Ic degradation and the interaction on strain effect were discussed in this study.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.65-67
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• 2003

The critical current of Bi-2223/Ag HTS wire could be improved by the second phase modification pre-treatment (SPMT). On the other hand, the pre-treatment conditions are possible to affect to the degradation of silver alloy sheath, such as brittleness. Chlorine was detected at the outer sheath of wire by Auger observation, we also have tried to search new pre-treatment conditions that do not affect the degradation of silver sheath but, improve the critical current of the wire.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.298-299
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• 2005

Differently from the tensile, transverse compression and torsion cases, the bending test of HTS tapes requires a lot of time and efforts, since the sample should be mounted successively onto bent sample holders in the order of decreasing radius and measuring the $I_c$ at each step. The influence of repeated cooling and warming experienced during these processes on the $I_c$ degradation can not be ignored. As a result, in this study, particularly. a new one-body type sample holder which provides continuous bending strains at 77K was devised. And, $I_c$ degradation behavior of Bi-2223 tapes under easy bending condition was investigated and compared that with other cases using Goldacker-type bending tester or respective sample holder.

• Progress in Superconductivity and Cryogenics
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• v.20 no.4
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• pp.31-35
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• 2018

When REBCO coated conductors (CCs) are applied to superconducting devices such as coils and magnets, they are subjected to deformation in various modes such as compression/tension bending, uniaxial/transverse tension and torsion. Despite outstanding performances by REBCO CC tapes, their electromechanical properties have been evaluated primarily under uniaxial tension, therefore data about the critical current ($I_c$) response in the compressive strain region are lacking. In this study, the characteristic responses of $I_c$ in REBCO CC tapes under bending strains in the range from tensile to compressive were evaluated. The springboard bending beam was used, wherein the CC tape sample was soldered onto the surface of the springboard. A Goldacker-type bending test rig, which lacks a support holding the sample during testing, was used as a comparator. Degradation in $I_c$ behaviors, including strain sensitivity, in differently processed REBCO CC tapes were examined based on the test rig used.