• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.93-94
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• 2006

The $I_c$ degradation behavior of YBCO CC tapes due to torsional deformation has been investigated. Particularly, the influence of torsion angle on the $I_c$ in HTS tapes was examined at 77K (self-field). At low torsional angles or shear strains, the $I_c$ degradation was small and gradual. Also, a good consistency of the $I_c$ degradation behaviors was found along the longitudinal direction under torsion when multiple voltage terminals were adopted for investigating the homogeneity of the $I_c$ degradation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.7
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• pp.630-635
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• 2000

Superconducting power cable is one of the most promising energy application of high-T$\sub$2/ superconductor(HTS). Thus we investigated previously the electrical and mechanical characteristics on Bi-2223 Ag sheathed tape. And a prototype HTS cable have been designed constructed and tested. In case of 19-filament type transport losses agree with the results of norris theory(strip). The critical current of HTS cable(1, 19-filament) in LN$_2$was 116[A], 240[A] and degradation coefficient(k) was 0.71, 0.73 respectively. In case of 19-filament cable critical current was decreased because of mechanical strain at pitch. And AC loss of HTS cable(19-filament) was 0.7 [W/m] in 240[A] loading

• Journal of the Semiconductor & Display Technology
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• v.3 no.4
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• pp.29-32
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• 2004

Fully depleted Silicon-on-Insulator (FD-SOI) devices lead to better electrical characteristics than bulk CMOS devices. However, the presence of a thin top silicon layer and a buried SiO2 layer causes self-heating due to the low thermal conductivity of the buried oxide. The electrical characteristics of FDSOI devices strongly depend on the path of heat dissipation. In this paper, we present a new three-dimensional (3-D) analysis technique for the self-heating effect of the finger-type and bar-type transistors. The 3-D analysis results show that the drain current of the finger-type transistor is 14.7% smaller than that of the bar-type transistor due to the 3-D self-heating effect. We have learned that the rate of current degradation increases significantly when the width of a transistor is smaller that a critical value in a finger-type layout. The current degradation fro the 3-D structures of the finger-type and bar-type transistors is investigated and the design issues are also discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1254-1257
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• 2004

This paper presents a built-in current sensor(BICS) that can detect defects in CMOS integrated circuits through current testing technique - Iddq test. Current test has recently been known to a complementary testing method because traditional voltage test cannot cover all kinds of bridging defects. So BICS is widely used for current testing. but there are some critical issues - a performance degradation, low speed test, area overhead, etc. The proposed BICS has a two operating mode- normal mode and test mode. Those methods minimize the performance degradation in normal mode. We also used a current-mode differential amplifier that has a input as a current, so we can realize higher speed current testing. Furthermore, only using 10 MOSFETS and 3 inverters, area overhead can be reduced by 6.9%. The circuit is verified by HSPICE simulation with 0.25 urn CMOS process parameter.

• Progress in Superconductivity and Cryogenics
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• v.24 no.3
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• pp.57-61
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• 2022

One of the major applications of REBCO coated conductor (CC) tapes is in superconducting magnets or coils that are designed for high magnet fields. For such applications, the CC tapes were exposed to a high level of stresses which includes uniaxial tensile or transverse compressive stresses resulting from a large magnetic field. Thus, CC tapes should endure such mechanical load or deformation that can influence their electromechanical performance during manufacturing, cool-down, and operation. It has been reported that the main cause of critical current (I_c) degradation in CC tapes utilized in coil windings for superconducting magnets was the delamination due to transversely applied stresses. In most high-magnetic-field applications, the operating limits of the CC tapes will likely be imposed by the electromechanical properties together with its I_c dependence on temperature and magnetic field. In this study, we examined the influence of the transverse compressive stress on the I_c degradation behaviors in various commercially available CC tapes which is important for magnet design Four differently processed REBCO CC tapes were adopted to examine their I_c degradation behaviors under transverse compression using an anvil test method and a newly developed instantaneous I_c measurement system. As a result, all REBCO CC tapes adopted showed robustness against transverse compressive stresses for REBCO coils, notably at transverse compressive stresses until 250 MPa. When the applied stress further increased, different Ic degradation behaviors were observed depending on the sample. Among them, the one that was fabricated by the IBAD/MOCVD process showed the highest compressive stress tolerance.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2001.02a
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• pp.17-20
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• 2001

Stress/strain dependencies of the critical current I$_{c}$ in AgMgNi sheathed multifilamentary Bi(2212) superconducting tapes were evaluated at 77K. The external reinforcement was accomplished by soldering Ag-Mg tapes to single side or both sides of the sample. With the external reinforcement, the strength of tapes increased but I$_{c}$ decreased. The I$_{c}$ degradation characteristic according to the external reinforcement was improved markedly in terms of the stress although it appeared less remarkable on the basis of the strain. Effects of external reinforcement were discussed in a viewpoint of monitoring sensitivity of cracking in superconducting filaments by considering n-value representing the transport behavior of the current, which is closely associated with the location of them relative to the voltage-monitoring region in the tape. tape.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.101-104
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• 2003

Influences of transverse compressive stress on the critical current ( $I_{c}$) in AgMg and AgMn alloy sheathed Bi-2223 tapes were investigated at 77 K and 0 T. The $I_{c}$ degradation behavior depending on sample specifications was discussed in viewpoints of n-value and damage morphology. As a result, Bi-2223 tapes showed a significant drop in $I_{c}$ for stresses greater than 50MPa. The AgMg sheathed Bi-2223 tapes representing higher $I_{c}$ showed a lower $\sigma$$_{irr}$ and a significant $I_{c}$ degradation with increase in compressive stress. There existed a voltage tap separation dependency of the $I_{c}$ degradation behavior caused by the transverse compressive stress.sive stress.s.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.05a
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• pp.9-9
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• 2009

Coated conductor is required to have good critical current property for high efficiency of electric power applications. Until now, long coated conductor does not show high Jc over 3 MA/$cm^2$ in thick superconducting layer because of texture degradation by thick superconducting layer. In this study, in order to overcome this issue, thicker superconducting layer was deposited with optimized conditions to reduce the degradation of critical current density. SmBCO superconducting coated conductor was deposited with 1~3 um of thickness at $750\sim850^{\circ}C$ under 15~20 mTorr of oxygen partial pressure using batch type EDDC( evaporation using drum in dual chamber). The buffered substrate for superconducting layer deposition was used IBAD-MgO template with the architecture of $LaMnO_3/MgO/Y_2O_3/Al_2O_3$/Hastelloy. After fabrication of coated conductor, critical current was measured by 4-prove method under self-magnetic field and 77K. In addition, surface morphology and texture were analyzed by SEM and XRD, respectively. 3 um thick SmBCO coated conductor shows highest $I_C$ values of 638A/cm-w in 1 m long in the world.

• Progress in Superconductivity and Cryogenics
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• v.9 no.3
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• pp.26-31
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• 2007

In recent years. YBCO coated conductor (CC) called as second generation HTS (high temperature superconducting) wire has been developed as a suitable material for resistive superconducting fault current limiter (SFCL). For designing the SFCL. the required length of superconducting wire is inverse proportional to the maximum temperature reached when a fault occurs. Since the required length strongly affects a manufacturing cost, it is the most important parameter to determine the maximum temperature reached. It is necessary to observe the repetitive over-current characteristics of HTS wire. This paper attempts to measure the variation of critical current of YBCO CC after repetitive over-current pulse. No degradation of the critical current of CC sample was observed by applying 100 times over-current pulse which makes temperature above 400 K after 100ms. This study can be useful in designing optimally resistive SFCL employing YBCO CC. The maximum permissible temperature can be set to 400K. so wire length could be reduced by 30% compared in case of 300K-criterion.

• Proceedings of the KIEE Conference
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• summer
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• pp.1067-1069
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• 2004

22.9[kV]/50[MVA]/30[m] HTS transmission power cable has been developed and tested at Korea Electrotechnology Research Institute and LG Cable Company by 21 century center for applied superconductivity technology. It is necessary to measure of critical current degradations, AC loss, insulation test and etc at the HTS cable development. This paper is analyzed characteristics that critical current of HTS cable bending condition according to this paper. We will be able to decide the diameter of drum which HTS cable is wound around and minimum curvature radius of HTS cable from results of this research.