• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 춘계학술대회 논문집
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• pp.198-201
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• 1996

In order to investigate control factors to critical current density, Ag sheathed Bi2223 superconducting tapes were fabricated using PIT process. Optimizing the reduction ratio of rolling, critical current density 7f rolled Bi2223 tape could be improved with the value of 15,000 A/$\textrm{cm}^2$(77 K, zero field). The correlation between J$\_$c/ and work inhomogeneity was revealed as a dependence of COV of measured oxide layer thickness.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 추계학술대회 논문집 학회본부 A
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• pp.236-242
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• 2000

NZP velocities were investigated on Ag sheathed multi filamentary Bi-2223 tape and direction type HTS cable. The critical current($I_c$) of Ag sheathed Bi-2223 tape and direction type HTS cable were 12 A, 63 A at 77 K, 0 T. NZP velocities of tape with two condition of DC and AC were almost same at each temperature. In case of DC, the NZP velocities of numerical analysis and experiment were almost same. NZP velocities of direction type HTS cable were 1.9-2.4 cm/sec. The result shows that the total transport current of spiral type HTS cable in $LN_2$ was 475[A], and transport current passed through almost the outer layer (2-layer). Also, AC transport losses in outer layer of HTS cable was proportion to $I^2$ and higher than losses of inner layer. And in case of $I_p=I_c$, calculated numerical loss density was concentrated on the edge of tape and most of loss density in cable was distributed outer layer more than inner layer.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제48권4호
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• pp.167-173
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• 1999

The use of high-Tc superconducting synchronous motor in power machinery has many advantages such as reduced power dissipation, size and weight. This paper presents the ac loss simulation in the rotor having an high-Tc superconducting field winding using Ag sheathed Bi-2223. The analysis was conducted with an equivalent model of the high-Tc superconducting motor with flux damper under transition condition during which the load varies from 0 watt to 250watts and from 250watts to 500watts. The simulation results show that the transient state lasts for about 3 seconds, and the ac losses decreased exponentially from the initial value above 20mW.

• 한국전기전자재료학회논문지
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• 제13권7호
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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

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 A
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• pp.349-352
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• 1998

In future superconducting electrical machines and device. AC loss in the superconducting windings are one of the most impotent design paramenters. This paper descriptions a series of Characteristic of a high-Tc superconducting Bi-Pb-Sr-Ca-Cu-O Ag-sheathed filament. In the case simulation and design to reduce ac loss is considered the filament number, twitch pith number and diameter of filament. A filament sample with Tc of 78K is made by $835^{\circ}C$ sintering for 50h and $0.33^{\circ}C$/min heating rate in an atmosphere. The experiment observations are compared with self-field loss and AC losses of Bi-Pb-Sr-Ca-Cu-O filament at 77K in following environments ; (i)AC external parallel magnetic field in different frequencies. And an analytical expression of the loss the derivation of transposition from an optimum condition was derived for the external AC magnetic field, theoretical predictions were found to coincide with the experimental observations.

• 한국초전도ㆍ저온공학회논문지
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• 제7권4호
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• pp.4-9
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• 2005

The degradation behavior of the critical current $(I_c)$ of Bi-2223 superconducting tapes under pressurized liquid nitrogen were investigated using a newly developed p-shaped sample holder which gives a series of bending strains to a sample. Three kinds of commercially available multi-filamentary Bi-2223 superconducting tapes were used. At atmospheric pressure, the Ie degradation behavior depended on the manufacturing process undergone by each tape. The tapes externally reinforced or densified by over pressure showed better bending strain tolerance than the Ag alloy-sheathed Bi-2223 tape. But these tapes showed a significant $I_c$ degradation when pressurized to 1 MPa in liquid nitrogen. For all samples, after depressurization to atmospheric pressure from 1 MPa, the Ie was completely recovered to its initial values at atmospheric pressure. When the samples were subjected to a thermal cycle wherein the tape was warmed up to room temperature after being depressurized from 1 MPa, it was found that the larger degradation of $I_c$ occurred at the regions where significant ballooning occurred, such as $0\%\;and\;0.2\%$. However, an improved ballooning damage tolerance was observed in the highly-densified tape.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 A
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• pp.125-127
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• 1998

Superconducting tape is being developed for electrical equipment such as superconducting transformers and generators. AC loss reduction is primary concern in the development of such high-efficiency equipment. AC losses in Bi-2223 silver-sheathed tapes, both single and multi-filamentary, were investigated by means of AC magnetization techniques. The results were compared with the hysteresis loss equation based on Bean model and the eddy current loss equation. The AC loss, of the mono-filamentary tape was the hysteresis. On the contrary, the AC loss of the multi-filamentary tape was substantially dominated by the eddy current loss in the Ag matrix.

• 한국초전도ㆍ저온공학회논문지
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• 제5권3호
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• pp.15-19
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• 2003

For the purpose of standardization of the critical current measurement, it is meaningful to describe how $I_{c}$ will behave as the stress/strain level changes. In this study, strain dependencies of the critical current $I_{c}$ in Ag-alloy sheathed multifilamentary Bi(2212) and Bi(2223) superconducting tapes were evaluated at 77K, 0T. The external reinforcement was accomplished by soldering AgMgNi alloy tapes onto single or both sides of the sample. With the external reinforcement to the Bi(2212) tape, the strength of the tapes increased but the critical current at the strain free state, $I_{c0}$ decreased in some cases. The strain for onset of the $I_{c}$ degradation, $\varepsilon$$_{\irr}$, increased with an increase of the reinforcing volume and then saturated to a certain value. The effect of external reinforcement on the degradation of $I_{c}$ due to the bending strain in the Bi(2223) tape was also examined. Contrary to the expectation, it showed a significant $I_{c}$ degradation even at a small strain of 0.4 %. The observations of damage morphologies gave a good explanation to the $I_{c}$ behavior.c/ behavior.r.

• 한국초전도ㆍ저온공학회논문지
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• 제4권1호
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• pp.13-16
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• 2002

$SrZrO_3 $resistive oxide barriers on Ag sheathed Bi2223 tapes were prepared by the sol-gel and dip coating method to reduce AC coupling loss. The performance of the dip-coated $SrZrO_3 $ thin films was evaluated in terms of bond strength by varying the Sr/Zr mol ratio and the amount of organic vehicle (ethyl cellulose and a-terpineol) additives. The bond strength of the coatings increased as the Sr/Zr ratio decreased and the amount of organic vehicle rose, respectively. It was found that the effect of organic vehicle addition was more pronounced, suggesting that the adherence of the $SrZrO_3 $ films on Bi2223 tapes was governed primarily by the amount of organic vehicle additive.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 학술대회 논문집
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• pp.146-148
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• 2003

SrZrO$_3$ resistive oxide barriers on Ag sheathed Bi2223 monocore tapes were prepared by the sol-gel and dip coating method to reduce AC coupling loss. The performance of the dip-coated SrZrO$_3$ thin films was evaluated in terms of bond strength and surface microstructure by varying the amount of PVP (polyvinylpyrrolidone) binder. Although bond strength and coating thickness increased as the PVP content rose, surface microcracking was more severe for the specimen containing higher content of PVP binder. It suggests that coating thickness and microcracking of the SrZrO$_3$ films on Bi2223 tapes was governed primarily by the amount of PVP binder.