• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1993년도 정기총회 및 추계학술대회 논문집 학회본부
• /
• pp.76-78
• /
• 1993

When an alternating current is supplied to a super-conducting multi-stranded cable, the quench current value of the cable was observed to be less than the simple summation of individual quench current value of each strand. One of the causes for such a degradation was attributed to the nonuniform of the current distribution in multi-stranded cable due to magnetic mutual coupling among the strands. The degradation of the superconducting cable is evaluated theoretically by taking into account the magnetic coupling among the strands.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1993년도 하계학술대회 논문집 B
• /
• pp.1078-1080
• /
• 1993

The quench performance and ramp rate sensitivity of eighteen 5-cm-aperature, 15-m-long SSC dipole magnet prototypes are discussed. All the magnets appear to reach a quench plateau near their extrapolated short sample current limit and well in excess of the operating current with very little training. Most of the magnets, however, exibit a dramatic degradation of thier quench current as a function of ramp rate, which for the most part, can be attributed to large cable eddy currents.

• 한국초전도ㆍ저온공학회논문지
• /
• 제3권2호
• /
• pp.5-9
• /
• 2001

For the development of a small-sized superconducting magnetic energy storage($\mu$SMES) system we designed, fabricated and tested a model coil consisting of five coils with different features. e.g. winding tensions. bore diameters and materials. cooling channels. The results show that even in the highly pre-stressed small coil the quench currents of the coils are degraded to about 70% of their coils critical current. The quench currents of the coils with natrow cooling channels are two times as high as that of the coil without spacers. The test results also indicate that the usual training effect depends on the winding tensions of the coils according to materials of the bobbin.

• 한국전기전자재료학회논문지
• /
• 제13권12호
• /
• pp.1058-1062
• /
• 2000

We investigated resistive superconducting fault current limites (SFCLs) fabricated using YBCO thin films on 2-inch diameter sapphire substrates. Nearly identical SFCL units were prepared and tested. The units were connected in series and parallel to increase the current and voltage ratings. A serial connection of the units showed significantly unbalanced power dissipation between the units. This imbalance was removed by introducing a shunt resistor to the firstly quenched unit. Parallel connection of the units increased the current rating. An SFCL module of 4 units in parallel, each of which has minimum quench current rating. An SFCL module of 4 units in parallel, each of which has minimum quench current 25 A$\_$peak/, was produced and successfully tested at a 220 V$\_$rms/circuit. From the resistance increase, we estimated that the film temperature increased to 200 K in 5 msec, and 300 K in 120 msec. Successive quenches revealed that this system is stable without degradation in the current limiting capability under such thermal shocks as quenches at 220 V$\_$rms/.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1996년도 하계학술대회 논문집 A
• /
• pp.37-40
• /
• 1996

Cable-In-Conduit Conductor(CICC) is widely accepted as an advanced superconductor configuration for large scale applications such as tokamak fusion reactors, MAGLEV (MAGnetic LEVitation), and SMES (Superconducting Magnetic Energy Storage). The stability of CICC cooled with supercritical helium can be very high if it is operated below a certain limiting current. This limiting current can be determined by Stekly type heat balance equation. The stability characteristic of CICC for AC operation is more complicated than that of DC because there are additional instability sources which are associated with local flux change. Ramp-rate limitation is a phenomenon discovered during US-DPC (United States-Demonstration Poloidal Coil) program, which showed apparent quench current degradation associated with high dB/dt. This paper describes recent experimental investigation results on the ramp-rate limitation and discusses current imbalance, induced current, current redistribution due to local quench of the strand in the cable.

• 한국초전도ㆍ저온공학회논문지
• /
• 제17권2호
• /
• pp.41-44
• /
• 2015

Critical current of high-temperature superconducting (HTS) coil is influenced by its own self magnetic field. Direction and density distribution of the magnetic field around the coil are fixed after the shape of the coil is decided. If the entire part of the HTS tape has homogeneous $I_c$ distribution characteristic, quench would be initiated in fixed location on the coil. However, the actual HTS tape has inhomogeneous $I_c$ distribution along the length. If the $I_c$ distribution of the HTS tape is known, we can expect the spot within the HTS coil that has the highest probability to initiate the quench. In this paper, $I_c$ distribution within the HTS coil under self-field effect is simulated by MATLAB. In the simulation procedure, $I_c$ distribution of the entire part of the HTS tape is assume d to follow Gaussian-distribution by central limit theorem. The HTS coil model is divided into several segments, and the critical current of each segment is calculated based on the-generalized Kim model. Single pancake model is simulated and self-field of HTS coil is calculated by Biot-Savart's law. As a result of simulation, quench-initiating spot in the actual HTS coil can be predicted statistically. And that statistical analysis can help detect or protect the quench of the HTS coil.

• 한국초전도학회:학술대회논문집
• /
• 한국초전도학회 2000년도 High Temperature Superconductivity Vol.X
• /
• pp.272-275
• /
• 2000

We investigated a resistive superconducting fault current limiter (SFCL) fabricated using YBCO thin films on 2-inch diameter sapphire substrates. Nearly identical SFCL units were prepared and tested. The units were connected in series and parallel to increase the current and voltage ratings. A serial connection of the units showed significantly unbalanced power dissipation between the units. This imbalance was removed by introducing a shunt resistor to the firstly quenched unit. Parallel connection of the units increased the current rating. An SFCL module of 4 units in parallel, each of which has minimum quench current 25 Ap, was produced and successfully tested at a 220 V circuit. From the resistance increase, we estimated that the film temperature increases to 200 K in 5 msec, and 300 K in 120 msec. Successive quenches revealed that this system is stable without degradation in the current limiting capability under such thermal shocks as quenches at 220 V.

• 한국초전도학회:학술대회논문집
• /
• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
• /
• pp.343-347
• /
• 1999

YBCO film을 이용한 meander 형태의 저항형 한류기에서 고장이 발생하였을 때 초기의 과도상태에서 볼수 있는 첨두전류를 억제하기 위하여 shunt 저항을 병렬로 취부한 경우의 전기적특성을 살펴보았다. 인가전압을 16.5 V$_{peak}$로 가하고 R$_0$는 1 ${\omega}$,R$_L$을 7.7 ${\omega}$으로 하고 shunt 저항을 5 ${\omega}$으로 하였을 때 약 12.2 A$_{peak}$의 전류값에서 최초quench가 발생하였으며 초전도 한류소자에 quench 발생으로 인한 저항이 발생함과 동시에 I$_1$으로 흐르던 사고전류의 일부가 shunt 저항이있는 I$_2$으로 서서히 분로하여 첨두전류가 거의 발생하지 않았다. 이때 초전도 한류기를 적용하지 않은 경우 최대 사고전류는 약 16.5 A$_{peak}$이었으며 초전도 한류기를 적용한 경우는 최대 한류전류값이 9 A$_{peak}$에서 4주기후에는 5.8 A$_{peak}$이었다. 인가전압 V$_0$=113 V$_{peak}$이고 표준저항 R$_0$는 1${\omega}$, 그리고 R$_L$을 7.7 ${\omega}$으로 하고 shunt 저항을 5 ${\omega}$으로 하였을 때 사고각 0 $^{\circ}$에서 사고전류값이 최고 23.0 A$_{peak}$까지 상승하고 이후 일정한 값을 유지하였다. 일반적으로 사고발생 직후에는 전류변화율에 의하여 전류값의 급격한 상승을 보이지만 shunt 저항이 전류분류의 역할을 수행하여 첨두전류는 거의 발생하지 않았다. 또한 상온의 gold층의 저항을 감안했을 때 사고발생후 약 36msec 후에 상온에 도달하였으며 shunt 저항이 없는 경우의 11 msec에 비하여 약 3배이상 길어졌다. 사고각 45 $^{\circ}$와 90 $^{\circ}$인 경우는 반복실험에 의한 시편의 특성저하(degradation)에 의하여 정상상태에서 초전도체에 흐르는 전류가 약간 발생하였다. 계통의 신뢰성이 중요한 요소로 작용하는 실제운전에서는 시편의 특성저하에 의한 quench전류의 감소를 감안하여 적절한 운전조건을 도출하여야 한다. 이상에서 앞으로는 장기간의 실제운전 조건을 고려하여 시편의 특성저하(degradation)와 가혹조건에 대한 전기적 특성에 대한 연구를 병행하고자 한다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1996년도 하계학술대회 논문집 A
• /
• pp.44-46
• /
• 1996

Superconducting cable is using by bundling and twisting with many strands for large current capacity. As a result of the twisting, the magnetic field whose direction is parallel to a sound axis by the transport current of themselves is produced in the cable. Not only the externally exposed longitudinal field but also longitudinal component of self field make a influence on a.c loss and a.c quench current degradation. In this paper, we calculate the saturated region flowing with the critical current density in a strand in case of various twist pitch, transport current and external longitudinal field.

• 환경생물
• /
• 제27권2호
• /
• pp.230-236
• /
• 2009

An extract of Allomyrina dichotoma larva (ADL), one of the insects used most frequently in traditional Chinese medicine for the treatment of liver diseases such as hepatocirrhosis and hepatofibrosis, was assessed for antioxidant bioactivity in this study. In the current work, we have investigated the protective effects of ADL extracts on tert-butyl hydroperoxide (t-BHP)-induced hepatotoxicity in cultured hepa1c1c7 cells and in the mouse liver. The treatment of the hepa1c1c7 cells with ADL extracts induced a significant reduction of t-BHP-induced oxidative injuries, as determined by cell cytotoxicity, lipid peroxidation (LPO) and reactive oxygen species contents, in a dose-dependent manner. Moreover, ADL extracts evidenced a protective effect against t-BHPinduced oxidative DNA damage, as revealed by the results of the Comet assay in hepa1c1c7 cells. ADL extracts also protected against hydroxyl radical-induced 2-deoxy-d-ribose degradation by ferric ion-nitrilotriacetic acid and $H_2O_2$. In addition, ADL extracts were shown to be able to quench 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radicals. Our in vivo study revealed that ADL extracts pretreatment applied prior to t-BHP administration significantly prevented an increase in the serum levels of hepatic enzyme markers and reduced LPO in the mouse liver in a dose-dependent manner. Taken together, these results suggest that the protective effects of ADL extracts against t-BHP-induced hepatotoxicity may be attributable, at least in part, to its ability to scavenge free oxygen radicals, and to protect against DNA damage due to oxidative stress.