• Progress in Superconductivity
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• 제4권2호
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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.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2003년도 High Temperature Superconductivity Vol.XIII
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• pp.67-67
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• 2003

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 한국초전도저온공학회 2002년도 학술대회 논문집
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• pp.241-244
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• 2002

We investigated over critical current characteristics of HTS tapes fabricated by KIMM. The critical current (Ic) of the HTS tapes was 68A/cm. In order to acquire over current I-V characteristics of HTS tapes, we applied AC that is 2-7 times of Ic to these tapes. When applied AC whose peak value is twice of Ic, we found out that total resistance of HTS tapes aid not change. In case of 3 times of Ic, resistances of HTS tapes began to increase slowly. However, superconducting regions of them were maintained stably in this condition. In addition, 280 $A_{peak}$was applied, superconducting regions began to be decreased gradually. Finally, 0.62m$\Omega$ of resistance was measured in HTS tapes which was applied AC correspond to 7 times of Ic at first cycle.

• Progress in Superconductivity and Cryogenics
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• 제9권3호
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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.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• 제16권5호
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• pp.424-428
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• 2003

The channel of a superconducting flux flow transistor has been fabricated with plasma etching method using a inductively coupled plasma etching. The ICP conditions then were ICP Power of 450 W, rf chuck power of 150 W, the pressure in chamber of 5 mTorr, and Ar : Cl$_2$=1:1. Especially, over the 5 mTorr, the superconducting thin films were not etched. The channel etched by plasma gas showed the critical temperature over 85 K. The critical current of the SFFT was altered by varying the external applied current. As the external applied current increased from 0 to 12 mA, the critical current decreased from 28 to 22 mA. Then the obtained trans-resistance value was smaller than 0.1 $\Omega$ at a bias current of 40 mA.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.365-366
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• 2009

This study researched into the manufacture of current-limit module of using YBCO coated conductor. Regarding over-current of exceeding the critical current, the quench characteristics were researched according to the stabilizing layer through tendency in resistance, which is generated in conductor, by applying over-current to YBCO coated conductors, which have stabilizing layer. YBCO coated conductors, which were used in experiment, include one kind such as the conductor, which used stainless as the stabilizing layer. The critical current is 70 A. And, the critical temperature is with 90 K. First of all, the quench generation was researched under over-current of exceeding the critical current by using this YBCO coated conductors. The tendency of a rise in the detected voltage according to the applied current was measured. And, the tendency of a rise in resistance through voltage-current curve was measured. As a result, the point of time in thermal quench of conductor, which has stainless as the stabilizing layer, could be confirmed to be fast.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 1993년도 추계학술대회 논문집
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• pp.35-38
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• 1993

SCLD(supercondocting current 1imiting device) with YBaCuO superconductor was fabricated by the sol-gel and the doctor-blade method. Critical current density ($J_{c}$) and critical current ($I_{c}$) of the SCLD are 100.27 A/$cm^2$and 1A at 77K and the electrodes contact with SCLD by silver paste. The SCL was connected with test circuit in series. When apple iud current exceed critical current value of the SCLD in testing circuit, the SCLD ristricts the over current by generating resistance itself without delay. Resistance of SCLD increase lineary 0 to 1.6$\Omega$ in propotion to applied current above the critical current $I_{c}$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.507-510
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• 2002

In economical points of view, AC loss of high temperature superconducting devices is considered as a serious problem that must be solved. Expecially, in case of HTS cables, HTS tapes are wound helically on the former to reduce AC loss. Critical characteristics of HTS tapes, however, are influenced by mechanical stress as well as electrical, temperature, and magnetical factors. The purpose of this study is to investigate the over current characteristics of HTS tapes given mechanical stress when they are wound on the former. We prepared HTS tapes with the pitch angle 20$^{\circ}$, length 25cm as well as tapes with pitch angle 0$^{\circ}$. When current of over 200A$\_$rms/ was applied, we found out that there are differences to the rate of resistance increase between the case of pitch angle 20$^{\circ}$and that of 0$^{\circ}$. The rate of resistance variation in HTS tapes of pitch angle 20$^{\circ}$increased more slowly than that of pitch angle 0$^{\circ}$. As a result, we concluded that if critical characteristics of HTS tapes are degraded by any external factor, when over current is applied, the current limiting characteristics in HTS tapes won't be able to be expected any more.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• 제17권6호
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• pp.678-682
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• 2004

Generally Bi-2223/Ag tapes have a broad S/N transition region and their sheath is a good electric conductor. In this study, the current distribution between superconductor and metal sheath in HTS tapes were investigated. AC with its peak value above 10 times $I_{c}$ was applied to HTS tapes for around 6 cycles and V-I characteristics were measured. Using the resistance of the sheath and V-I curves, the current distribution between superconductor and metal sheath was calculated. When 150 $A_{p}$ was applied, more than 2/3 of the current flows through superconductor. However, in the case of 304 $A_{p}$, most of the applied current came to flow through the metal sheath at the 6th cycle.e.e.e.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 한국초전도저온공학회 2000년도 KIASC Conference 2000 / 2000년도 학술대회 논문집
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• pp.128-129
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• 2000

The over-critical current behaviors for bare or insulated Bi-222 tapes with different matrix materials have been examined. The result shows that static resistances of the two bare tapes becomes similar for currents above 150 A but different for currents below. In the insulated A tape the first rapid temperature rise occurred around 180 A and eventually burned out about 190A.