• Progress in Superconductivity
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• v.4 no.2
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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.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.903-905
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• 2002

According to the improvement of the HTS wires performance, several types of HTS superconducting machines, such as, transformer, motors, current limiters, and transmission cables are being developed. Degradation of the critical current in HTS tape owing to external field is very important subject in developing the HTS machines. Considering that stacked HTS tapes are widely used to develop the large HTS machines, the critical current characteristics of stacked HTS tapes in external field need to be examined. In this paper, we present critical current characteristics of 4-stacked HTS tapes which are exposed to the external field. HTS tape with critical current of 4-stacked HTS tape. Test results prove that four times critical current of single HTS tape is smaller than critical current of stacked HTS tape in high external field.

• Progress in Superconductivity and Cryogenics
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• v.21 no.4
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• pp.24-28
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• 2019

Despite the second generation HTS tapes (2G HTS tape) have limits in critical current value, scientific and electric devices require more current density day after day. These requirements are realized by using different superconducting wires that consist of 2G HTS tapes designed in various combinations. Authors of this paper have developed the numerical model for estimation of total critical current in the superconducting wire and critical current in each 2G HTS tape placed in this superconducting wire. The current drop in six 2G HTS tapes having different constructions was analyzed. The result of this research is the decrease of critical current up to 25 % for the stack of tapes and up to 5 % for the parallel tapes in the same plane. In addition, what was also made is the estimation of the current distribution by length for six 25 m 2G HTS tapes in different constructions and determination of current deviation by length of the wire.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.903-905
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• 2003

High temperature superconductor (HTS) tapes are now commercially available for practical applications to apply various purposes. However HTS tapes show different electrical and mechanical characteristics, according to the manufacturers who are trying to apply various fabrication processes and treatments. From the viewpoint of an application it is very important to investigate the properties of HTS tapes under mechanical stress because the tapes will be wound with twisting and tension in applications such as magnets and cables. Thus, we studied characteristics of HTS tapes and measure critical current under bending, considering of a mechanical conditions. A description of some typical results will be presented with discussions.

• Progress in Superconductivity and Cryogenics
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• v.17 no.1
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• pp.48-52
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• 2015

The electrical insulation design for a superconducting coil system is important for developing high voltage superconducting apparatuses. Also, the degraded characteristics of superconducting tapes due to an electrical breakdown should be considered for superconducting coils design. In this study, the degradation characteristics of 2G high temperature superconducting (HTS) tapes were studied with respect to electrical breakdown tests. The degradation tests of 2G HTS tapes were performed with various stabilizer materials. The degradation characteristics of 2G HTS tapes such as critical current(Ic) and index number were observed by performing electrical breakdown tests. It was found that the characteristics such as Ic and index number can be degraded by an electrical breakdown. Moreover, it was concluded that the degradation characteristics of 2G HTS tapes were affected by a stabilizer material and applied breakdown voltage. The cross sectional view of 2G HTS tapes was observed by using a scanning electron microscope (SEM). As results, it is found that the degradation characteristics of 2G HTS tapes are concerned with hardness and electrical resistivity of stabilizer layers.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.551-554
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• 2004

Bi-2223 HTS tapes are used widely for application of superconducting power systems. However there are need the properties of high strength and low AC loss. Two kinds of Bi-2223 HTS tapes with different Ag sheath were used to know the effect of sheath alloying for the strength and the resistivity. The workability and reaction degree of superconducting phase at Bi-2223 HTS tapes were investigated. We designed conventional type-Ag/alloy and double sheathed mono filament type-Ag/alloy/alloy in order to increase the strength and resistivity of matrix in Bi-2223 HTS tapes. The effect of axial strain and thermal cycling on the critical current was investigated for the Bi-2223 HTS tapes. Because the workability of double sheath Bi-2223 HTS tape was lower than one sheath Bi-2223 HTS tape, it was need additional softening treatment. Bi-2223 formation reaction was decreased by Ag alloy matrix during sintering process. Two kinds of Bi-2223/Ag tapes with different Ag sheath were used to know the effect of sheath alloying for the tensile strain. Critical current is drastically decreased for Ag/alloy and Ag/alloy/alloy sheathed tapes at tensile strain above 0.24 % and 0.34 %, respectively. This result showed that mechanical strength was increased over than 40 % by introduce double sheath at mono filament stage.

• Progress in Superconductivity and Cryogenics
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• v.17 no.2
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• pp.50-53
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• 2015

The properties of High Temperature Superconducting (HTS) tapes are progressing, as HTS tapes evolve from 1st generation to 2nd generation. This paper presents design and construction of a 2nd generation HTS magnet consisting of two nested GdBCO and YBCO pancake coils. Two HTS tapes of different widths were used to wind the HTS nested magnet. Considering that a higher magnetic field is applied to the inner magnet than to the outer magnet, 12 mm GdBCO tape was used for winding the inner magnet, which consisted of four single pancake windings. Eight double pancake windings wound with 4.4 mm YBCO tapes were used for the outer magnet. The test results show that the central magnetic field of the HTS nested magnet was 920 mT. The measured critical currents of the inner and outer magnet at 77K were 80.8 A and 32.6 A, respectively.

• Progress in Superconductivity and Cryogenics
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• v.24 no.3
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• pp.47-51
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• 2022

With the innovative development of bio, pharmaceutical, and semiconductor technologies, it is essential to demand a next-generation transfer system that minimizes dust and vibrations generated during the manufacturing process. In order to develop dust-free and non-contact transfer systems, the high temperature superconductor (HTS) bulks have been applied as a magnet for levitation. However, sintered HTS bulk magnets are limited in their applications due to their relatively low critical current density (J_c) of several kA/cm² and low mechanical properties as a ceramic material. In addition, during cooling to cryogenic temperatures repeatedly, cracks and damage may occur by thermal shock. On the other hand, the bulk magnets made by stacked HTS tapes have various advantages, such as relatively high mechanical properties by alternate stacking of the metal and ceramic layer, high magnetic levitation performance by using coated conductors with high J_c of several MA/cm², consistent superconducting properties, miniaturization, light-weight, etc. In this study, we tried to fabricate HTS tapes stacked bulk magnets with 60 mm × 60 mm area and various numbers of HTS tape stacked layers for magnetic levitation. In order to examine the levitation forces of bulk magnets stacked with HTS tapes from 1 to 16 layers, specialized force measurement apparatus was made and adapted to measure the levitation force. By increasing the number of HTS tapes stacked layers, the levitation force of bulk magnet become larger. 16 HTS tapes stacked bulk magnets show promising levitation force of about 23.5 N, 6.538 kPa at 10 mm of levitated distance from NdFeB permanent magnet.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.277-280
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• 2002

It is well known that the critical current of a HTS tape has anisotropic characteristic in magnetic field. We are interested in critical current density distribution of a HTS tape. We assumed the experimentally obtained Ic-B curves do represent the local properties of HTS tapes and calculated the critical current density distribution of HTS tapes using numerical method. Also we predicted the critical current of the tapes.

• Progress in Superconductivity and Cryogenics
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• v.10 no.1
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• pp.32-36
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• 2008

An HTS conductor with parallel HTS tapes is essential for a large power HTS device to flow a large current. One of the most important factor for this conductor is a current distribution. Non-uniform current distribution in parallel tapes makes the critical current of the conductor low and the AC losses high. In this paper we proposed a non-contact method which measured each current in parallel tapes by using an array of Hall sensors. A matrix can be derived from this array for calibration. The current distributions of 4 and 6 parallel tapes were measured.