• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2001.02a
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• pp.145-148
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• 2001

Bi-2223/Ag HTS tapes fabricated by PIT process are used to make the power transmission cable, motor, fault current limiter, transformer etc. But some problems are still remained as like bubbling, sausaging to got the high Jc. In this study. we carried out the experiment to prevent bubbling in the HTS tape. The bubbling mainly occurred when HTS tape was heat-treating. Therefore, additional vacuum annealing at 400 ~ $600^{\circ}C$and slowly ramp-up sintering method were used to decrease the bubbling. slowly ramp-up sintering was more effective to decrease the bubbling than the vacuum annealing, but Jc was also decreased after heat treatment. Optimum ramp-up sintering schedule was searched to get the high critical current and prevent bubbling at same time.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 1999.02a
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• pp.54-57
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• 1999

AC losses per cycle properties at 77K have been investigated on the Ag sheathed Bi2223 wire through two kinds of measuring methods(transport method and magnetic method). In case of transport method, the absolute value of losses agree with the results of Norris theory(strip and ellipse). In case of 19-filamentary tape, AC transport losses almost agree with those of magnetic method. In case of 1-filamentary tape, However, AC losses of magnetic method is smaller than AC transport losses

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2000.02a
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• pp.170-172
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• 2000

This paper deals with the characteristic analysis of the flux damper with respect to the load, and the stability of Ag/Bi-2223 tapes in a high-Tc superconducting (HTS) synchronous motor. To find out the magnetic field distribution in a detailed model of the actual motor, the experimentally measured currents of the armature and the field windings are used as input parameters. The simulation results show that the flux damper shields the time varying field up to 10%, reduces armature reactance during the motor operation and during load changes, improving the stable motor operation. And it was observed that the flux damper generates loss by means of leakage flux, but this is not significant and it doesn't degrade the performance of the TS synchronous motor.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1551-1553
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• 2000

Superconducting power cable is one of the most promising energy application of high-$T_c$ superconductors (HTS). A prototype HTS cable have been constructed multi-layer cable using Bi-2223 tape and tested. The result shows that the total transport current of 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. As magnetic distribution were concentrated on outer layer.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.603-604
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• 2000

Bi-2223 테이프는 송전케이블과 같은 저 자장 전력시스템의 응용에 가장 유망한 선재로 알려져 있다. 송전케이블에 교류 전류가 인가되면 인접한 테이프에 의해서 발생되는 자계는 통전손실에 영향을 미치게 된다. 이와 같은 실제 송전케이블의 응용 측면을 고려하여 좌측 및 상부인접전류가 통전손실에 미치는 영향에 대하여 조사하였다. Bi-2223 테이프의 통전손실은 교류 인접전류가 증가함에 따라서 급격하게 증가하는 반면, 직류 인접전류의 영향은 무시 가능한 정도로 작았으며, 인접전류가 큰 경우는 테이프의 배열에 무관한 반면 작은 경우에는 상부배열인 경우의 영향이 큼을 알 수 있었다. 또한 Bi-2223 테이프의 통전손실은 교류 인접전류의 주파수에 무관함을 알 수 있었다.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.10a
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• pp.260-262
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• 2003

AC loss is an important issue in the design of high-T$_{c}$, superconducting power cables which consist of a number of Bi-2223 tapes wound on a cylindrical former. In this paper, the ac loss characteristics in the 3-conductor have investigated experimentally. The loss test results indicate that the ac loss is not related to the arrangement of Bi-2223 tapes, contact position and applied frequency. The measured losses in face-to-face arrangement are larger than those in edge-to-edge arrangement. The measured losses in the 3-conductor also agree well with the sum of the transport losses measured in each Bi-2223 tape.e.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.792-794
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• 2003

AC loss is an important issue in the design of high-$T_c$ superconducting power cables which consist of a number of Bi-2223 tapes wound on a former. In the cables, the tapes have different critical currents intrinsically. And they are electrically connected to each other and current leads. In this work we have prepared a conductor composed of three Bi-2223 tapes with different critical currents. The critical current characteristics in the conductor have experimentally investigated. The results show that for uniform current distributions the conductor's critical current is proportional to the critical current of the Bi-2223 tape to which a voltage lead is attached. However it depends on the current non-uniformity parameter in the conductor rather than the tape's critical currents for nonuniform current distributions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.235-238
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• 2000

There have been a lot of studies to improve the characteristic of Bi-2223 tape by PIT method which is considered as one of the best way for applying superconductor. These improved characteristic of Bi-2223 tape is able to be acqured by control of mechanical deformation and heat treatment. In this work, we studied HTS tapes with the sheath(Ag and Ag-alloy)of tapes that affect mechenical strength and critical current, with each two kind of purity(99.9% and 99.999%) and with two kind of tapes(single and double concentric). These charateristics affect Jc of tapes seriously that is the most important factor of superconductor tapes.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05a
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• pp.25-29
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• 2003

Pre-treatment of Bi-2223/Ag tapes has been investigated to improve the superconducting property and grain alignment. However, rolling deformability of Bi-2223/Ag wires was degraded by the breakage of Ag alloy sheath after pre-treatment. Various pre-treatment conditions were tried to prevent the problem of sliver sheath and improve the superconducting property of Bi-2223/Ag tapes. Filament precursor of Bi-2223/Ag tapes was modified to be textured easily during main sintering by the optimum pre-treatment with low oxygen pressure and up to $800^{\circ}C$. Critical current was also increased up to 20% than that of no pre-treated tape.

• Journal of the Korean Ceramic Society
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• v.35 no.2
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• pp.137-144
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• 1998

High-temperature superconducting joints between 61 filaments of Bi-2223 tapes were fabricated by chem-ical corrosion and repeated thermomechanical process. The silver sheath of the superconducting tape was chemically removed using chemical etchant(NH4OH:H2O2=1:1) from one side of each tape without altering the form of lap joint. The joined region was formed by uniaxial pressing and a series of thermomechanical process and then subjected to properties measurement and microstructural analysis. The critical current(Ic) variation and I-V characteristics along the joint were mesured with several configuration of proble points. Ic value of the transition region of the joint inthe multifilament tape which limit the total current carring capacity of the superconducting tape was higher than that of monofilament tape. But the transition ex-ponent n-value of the multi-filament tape was lower than that of monofilament wire due to the interaction of the individual superconducting core of the multi-filament. The critical current through the joint area was improved by respeated press and reaction annealing treatment.