• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.44-44
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• 2010

Conventional water treatment facilities like precipitation process need large-scale equipment and wide space to purify the wastewater of paper factory. In case of massive waste water, high gradient magnetic separation (HGMS) parts are more effective to purify it rapidly and to occupy relatively small space, since large voids at filter with HGMS are adopted. Cryo-cooled Nb-Ti superconducting magnet with room temperature bore in diameter of 100 mm and 600 mm in height was used for magnetic separator. Magnetic filters were designed by the analysis of magnetic field distribution at superconducting magnets.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.2
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• pp.96-100
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• 2017

In this paper, the flux-lock type superconducting fault current limiter (SFCL) using double quench was suggested and its transient current limiting characteristics were analyzed. The suggested flux-lock type SFCL using double quench consists of two magnetically coupled windings and two $high-T_{c}$ superconducting (HTSC) elements connected in series with each winding. To analyze the transient current limiting characteristics of the flux-lock type SFCL using double quench, the short-circuit tests according to the fault angles, which affect the transient component of the fault current right after the fault occurs, were executed. From the comparative analysis for the short-circuit tests at both $0^{\circ}$ and $90^{\circ}$ fault angles, the useful transient current limiting operations of the suggested flux-lock type SFCL through the double or the single quench occurrence were confirmed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.2
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• pp.101-105
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• 2017

In this paper, the magnetization characteristics and the stored energy of magnetically coupled superconducting fault current limiter (SFCL)s using single and double high-Tc superconducting (HTSC) elements were compared. To analyze the magnetization characteristics and the stored energy, the magnetizing current and the flux linkage, which were derived from the electrical equivalent circuit of the SFCL using single and double HTSC elements, were calculated from the voltages and the current measured in the short-circuit tests. Through the comparative analysis on the magnetization characteristics and the stored energy for SFCL using sing and double HTSC elements, the magnetically coupled SFCL using double HTSC elements was shown to be more effective than the SFCL using single HTSC element from the point of view of the magnetic saturation.

• Progress in Superconductivity and Cryogenics
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• v.4 no.1
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• pp.30-34
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• 2002

In this Paper, Insulation of current lead in the conduction-cooled DC reactor for the 1.2kV class 3 high-Tc superconducting fault current limiter(SFCL) is studied. Thermal link which conducts heat energy but insulates electrical energy is selected as a insulating device for the current lead in the conduction-cooled Superconducting DC reactor. It consists of oxide free copper(OFC) sheets, Polyimide films, glass fiberglass reinforced Plastics (GFRP) plates and interfacing material such an indium or thermal compound. Through the test of dielectric strength in L$N_2$, polyimide film thickness of 125 ${\mu}{\textrm}{m}$ is selected as a insulating material. Electrical insulation and heat conduction are contrary to each other. Because of low heat conductivity of insulator and contact area between electrical insulator and heat conductor, thermal resistance of conduction-cooled system is increased. For the reducing of thermal resistance and the reliable contact between Polyimide and OFC, thermal compound or indium can be used As thermal compound layer is weak layer in electrical field, indium is finally selected for the reducing of thermal resistance. Thermal link is successfully passed the test. The testing voltage was AC 2.5kVrms and the testing time was 1 hour.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.159-160
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• 2005

The superconducting fault current limiter(SFCLs) provides the effect such as enhancement in the power system reliability due to limiting fault current in a few miliseconds. The Flux-lock type SFCL using the YBCO film among various type SFCLs consists of the primary and the secondary copper coils that are wound in parallel each other through the iron core. The operation can be controlled by adjusting the inductances and the winging directions of each the coil. We compared the current limiting performance on the additive and the subtractive polarity winding directions in case of an open-loop iron core. To analyze quench characteristics, we experimented various phase angle.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.153-154
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• 2005

A high Tc superconducting with a nominal composition of $Bi_2Sr_2Ca_2Cu_3O_Y$ was prepared by the citarte method. The solid precursor produced by the dehydration of the gel at 120$^{\circ}C$ for 12h is not in the amorphous state as expected but in a crystalline state. X-ray diffraction peaks of nearly the same angular position as the peaks of high Tc phase were observed in the precursor. After pyrolysis at 400$^{\circ}C$ and calcination at 840$^{\circ}C$ for 4h, the (001)peak of the high Tc phase was cleary observed. Experimental results suggest that the intermediate phase formed before the formation of the superconducting phase may be the most important factro in determining whether it is easy to form the high Tc phase or not, because the nucleation barriers of the two superconducting phase may be altered by the variation of the crystal structures of those intermediate phase.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.155-156
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• 2005

We investigated the quench characteristics of the flux-lock type superconducting fault current limiter (SFCL) integrated three-phase according to fault types such as the single-line-to-ground fault, the double-line-to-ground fault and the three-line-to-ground. The structure of integrated three-phase flux-lock type SFCL consists of single core which have three-phase flux-lock reactors. The superconducting elements connected sound phase as well as fault phase happened to quenching. Therefore we conformed that the superconducting elements were dependent.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.546-549
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• 2003

The principle of the superconducting vortex flow transistor (SVFT) is based on control of the Abrikosov vortex flowing along a channel. The induced voltage is controlled by a bias current and a control current, instead of external magnetic field. The device is composed of parallel weak links with a nearby current control line. We explained the process to get an I-V characteristic equation and described the method to induce the external and internal magnetic field by the Biot-Savarts law in this paper. The equation can be used to predict the I-V curves for fabricated device. From the equation we demonstrated that the current-voltage characteristics were changed with input parameters. I-V characteristics were simulated to analyze a SVFT with multi-channel by a Matlab program.

• Progress in Superconductivity and Cryogenics
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• v.7 no.2
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• pp.31-34
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• 2005

There are many kinds of high temperature superconducting (HTS) application using Bi-2223 tape which is the most commercialized HTS material. Also, resistive superconducting fault current limiters (SFCLs) have been developed using many kinds of superconducting material such as YBCO thin film, Bi-2212 bulk and so on. However, SFCL using Bi-2223 tape has never been developed. This paper deals with the feasibility study on SFCL using Bi-2223 wire. The over-current behaviors of Bi-2223 short-length sample were measured. To make the resistive SFCL, two small-scale bifilar winding modules using 7m Bi-2223 wire were fabricated; i.e. solenoid type bifilar coil and pancake type one. The short-circuit tests of the coils were successfully performed up to 16 V$_{rms}$ From these tests, the current limiting capabilities of Bi-2223 bifilar coils were confirmed and current limiting performances between two winding types were compared. In addition, the feasibility of resistive SFCL using another HTS wire, i.e. YBCO coated conductor, was also investigated.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.12S
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• pp.1286-1291
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• 2003

Quench behavior of resistive superconducting fault current limiters (SFCLS) with various pattern shapes was investigated. The pattern shapes employed were meander, bi-spiral, and spital shapes of identical line width, gap and margin. SFCLS were fabricated from YBCO thin films grown on two-inch diameter Al$_2$O$_3$ substrates under the same conditions. The total length of current limiting paths was the shortest at the spital shape due to its larger useless space. Inductance component of SFCLs with the spiral shape was around two times as high as those of other two shapes. This is not desirable since impedance characteristics of existing power systems can be changed. Resistance rise of current limiting elements was low at a spiral shape before the whole quench completion, which may act as a disadvantage for simultaneous quench in serial connection between current limiting elements, but the temperature tended to have similar values at higher voltages. On the other hand, hi-spital shape was severe at insulation level between current limiting lines. When these aspects were considered, we concluded that a meander shape was appropriate to design for a resistive SFCL based on thin films except the concentration of electric field at edge areas of strip lines.