• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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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.

• KIEE International Transactions on Power Engineering
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• v.3A no.2
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• pp.100-108
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• 2003

This paper presents the design and performance results of a pair of 6-kA high-temperature superconducting (HTS)-copper current leads, in which, over a short length at the warm end (e.g.,77K) of each HTS section, comprised of paralleled Bi-2223/Ag-Au tapes, is operated in the current-sharing mode. Because of their reliance on vapor cooling, the leads are applicable only to liquid helium cooled superconducting magnets such as those used in high-energy Physics accelerators and fusion machines. The experimental measurements have demonstrated that key performance data of the new 6-kA HTS-Copper leads agree reasonably well with those expected from design.

• Progress in Superconductivity and Cryogenics
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• v.9 no.4
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• pp.41-45
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• 2007

Superconductor is developed for applications in high-power devices such as power-transmission cables, transformers, motor and generators. In such applications, HTS tapes are subjected to various kinds of stress or strain. AC loss is also important consideration for many large-scale superconducting devices. In the fabrication of the devices, the critical current $(I_c)$ of the high temperature superconductor degrades due to many reasons including the tension applied by bending and thermal contraction. These bending or tension reduces the $I_c$ of superconducting wire and the $I_c$ degradation affects the AC loss of the wire. The $I_c$ degradation and AC loss (self field loss) of Bi-2223 HTS and Coated conductor were measured under tension and bending conditions at 77K and self-field.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.149-152
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• 2002

SrZrO3 resistive oxide barriers on Ag sheathed Bi2223 tapes prepared by the sol-gel and dip coating method were evaluated with an aid of Taguchi method and orthogonal arrays to elucidate the effects of experimental parameters, such as ratio of starting solution, amount of additives, and heat treatment temperature and time on the properties of the thin films. Six experimental parameters were selected and then Ll8(21x37) orthogonal arrays were constructed. Finally, SEM and XRD results were related to signal to noise (S/N) ratio to evaluate the optimized experimental condition.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.271-273
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• 2002

The ac loss in Bi-2223 tapes has been studied by a magnetic method. A brief overview of the theoretical background and the experimental set-up is presented. Measurements are made at 77 K in a magnetic fields. The magnitude of the ac loss indicates that filaments are fully coupled, which agrees with theory. As in other measurements, the loss in perpendicular field is larger than that in the parallel field by about a factor 10, which is close to the aspect ratio of the tape.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.186-191
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• 2000

Stability of a Bi-2223/Ag tape was studied by using a numerical method. A numerical modeling has been developed to analyze the dynamic evolution of normal zone in a composite tape Bi-2223/Ag. In this paper, the stability of HTS tape is studied by considering the non-uniform temperature distribution in a cross-sectional area. The finite-difference method(FDM) is used to solve the two-dimensional heat conduction equation. Two kinds of analyses are compared to quantify the critical disturbance energy fur quenching HTS tapes. One is the length-thickness(x-y) side and the other is the length-width(x-z) side. The results of analyses shows that the critical disturbance energies for each cases seem to be very close for considered Bi-2223/Ag tape.

• 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 Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.65-67
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• 2003

The critical current of Bi-2223/Ag HTS wire could be improved by the second phase modification pre-treatment (SPMT). On the other hand, the pre-treatment conditions are possible to affect to the degradation of silver alloy sheath, such as brittleness. Chlorine was detected at the outer sheath of wire by Auger observation, we also have tried to search new pre-treatment conditions that do not affect the degradation of silver sheath but, improve the critical current of the wire.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.3
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• pp.247-253
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• 2000

We evaluated the electric properties of Bi-2223 jointed tapes processed by both resistive-and superconducting-joint methods. For resistive-joint. filler materials of wood metal Pb/Sn. In and silver paste were used whereas for superconductive-joint lap joint method was used. In the resistive joint tape. critical transport property(CCR) n-value and contact resistance were observed to be in the range of 10-85% 1-8,9. and 0.71x10$\^$-6/-0.13x10$\^$-6/Ω, respectively. depending on their filler materials. Specifically it is believed that the electrical properties of resistive joint tape are significantly related to the resistivity of filler materials. On the other hand the CCR of superconductin joint type was varied 55 to 85% with uniaxial pressure probably due to the irregular microstructure in the transition region.

• Progress in Superconductivity and Cryogenics
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• v.7 no.1
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• pp.47-50
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• 2005

The AC loss is an important issue in the design of the high temperature superconductor (HTS) power cables, which consist of a number of lli 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. These make loss measurements considerably complex, especially for short samples of laboratory size. In this work we have prepared a multi-tape conductor composed of Bi-2223 tapes. The at losses of the conductor have experimentally investigated. The loss tests indicate that the effect of tapes critical currents on AC loss measurement in the multi tape conductor is negligible only if currents in the tapes flow uniformly Moreover, the measured tosses of the conductor are in good agreement with the sum of the transport losses in the tapes. However, in the case of non-uniform current distributions, the measured AC losses considerably depend on the current distribution parameter of the positioning of a voltage lead. Thus special cautions should be needed for the measurement of the true AC losses in the short power cable samples.