• Progress in Superconductivity and Cryogenics
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• v.13 no.4
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• pp.26-29
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• 2011

In a High temperature superconducting (HTS) tape with high aspect ratio, the magnetic field applied to the HTS tape can be different considerably within the HTS tape. The current distribution in the HTS tape is generally non-uniform because the current distribution is strongly dependent on the applied magnetic field. Non-uniform current distribution in a HTS tape has not been properly considered when the critical current has been estimated. This paper shows the calculation of critical current of a HTS magnet consisting of pancake windings. Non-uniform distribution of current in the HTS tape is considered during the calculation of the critical current. Results of calculation show the current concentrated in the middle part of the HTS tape which is used for one pancake winding.

• Progress in Superconductivity and Cryogenics
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• v.17 no.3
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• pp.47-50
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• 2015

The high temperature superconducting (HTS) magnet has been developed for the high magnetic field applications such as NMR, MRI and other industrial machinery. In designing process of these HTS magnets, the accurate estimation on the critical current (Ic) is essential to predict and secure the electromagnetic performance. The critical current of 2G HTS tape has anisotropic Ic degradation characteristics with the application of magnetic field - angular dependency of critical current. It is known that the perpendicular magnetic field to the face of HTS tape makes dominant degradation on the critical current for conventional 2G HTS tape. However, recently developed 2G HTS tape has more complex characteristics due to the artificial pinning center. Therefore, the method for Ic estimation reflecting such characteristics of 2G HTS tape needs to be devised. The method considering the angular dependency is introduced in this paper. And the result of newly devised method is compared with that of previous method.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.378-382
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• 1999

We evaluated the effect of joining process such as contact method, shape of joined area and pressure on the electrical property of Bi-2223 superconducting tape. It was observed that the current capacity was reduced at the transition area of the joined tape and was significantly dependent on the uniaxial pressure. The lap-joined tape, fabricated with a pressure of 1,000-1,600 MPa, show the highest value of current capacity(80-90%) of the tape itself. It is believed the highest value of current capacity results from improvement in core density, contacting area and grain alignment, etc. In addition, the irreversible strain( ${\varepsilon}$ irrev) for the joined tape· was measured to be 0.1%, smaller than that of enjoined tape( ${\varepsilon}$ irrev = 0.3%). The decrease in the strength and irreversible strain for joined tape is believed to be due to the irregular geometry/morphology of the transition area of the tape.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.280-290
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• 1999

The microstructures of a Tl$_{0.8}Pb_{0.2}Bi_{0.2}Sr_{1.6}Ca_2Cu_3O_{9+{\delta}}$/Ag tape (tape I ) with J$_c$ of 17,600 A/cm$^2$ at 77 K and 0 T and three Tl$_{0.8}Pb_{0.2}Bi_{0.2}Sr_{1.8}Ba_{0.2}Ca_{2.2}Cu_3O_{9+{\delta}}$/Ag tapes with J$_c$'s of 9,300 (tape II), 16,700 (tape III) and 25,200 A/cm$^2$ (tape IV)prepared using the powder-in-tube method and an in-situ reaction method, were investigated using scanning electron microscopy and high-resolution transmission electron microscopy, and compared each other. ln the tape preparation, an intermediate rolling process was incorporated during final heat-treatment for the last tape, but not for the rest of the tapes. The microstructural analysis revealed clear differences in grain-texturing, crystallographic defects and impurity phases, depending on the chemical composition of the tape. Tendency of directional grain-alignment increased in an order of tapes I, II III and IV. In tape IV, T1-1223 grains are textured, at least in local regions. In crystallographic defects, while stacking faults were prevalent in the former composition, dislocations and voids were frequently observed in the latter. Also impurity phases were appeared to be more abundant in the former than in the latter. The relationship between 1,and the microstructure in the tapes was attempted to explain in a term of grain-linking.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.101-104
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• 2002

The influences of the powder packing density on the Bi-2223/Ag tape have been investigated. For packing powder, both method of uniaxial press and packed rod form made by cold isostatic press(CIP) have been applied. As the pressure of cold isostatic press(CIP) is increased, fill factor and critical current (Ic) of Bi-2223/Ag tape is increased. At a pressure of 2000kgf/cm$^2$, fill factor reach ∼3l% and this sample has the engineering current density(Je) value of ∼8.5kA/cm$^2$(Ic ∼77A, Jc ∼ 30kA/cm$^2$). The tape sample packed by uniaxial press method shows more sawsaging effect than the sample processed by cold isostatic press(CIP), resulting from inhomogity of powder distribution produced by the process of uniaxial press.

• Progress in Superconductivity and Cryogenics
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• v.15 no.3
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• pp.9-12
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• 2013

Current-voltage characteristic models of superconducting material are suggested by many researchers. These current-voltage characteristic models are important because they can be used for design or simulation of superconductor devices. But widely used current-voltage models of superconductor wire still have some limitations. For example, a standard E-J power model has no parameters related with stabilizer's resistance in superconductor wire. In this paper, a current-voltage characteristic modeling method for high temperature superconductor (HTS) tape with considering the effect of stabilizer is introduced. And a current-voltage characteristic of a HTS tape is measured under different stabilizer conditions. Those measured current-voltage characteristics of the HTS tape modeled with proposed modeling method and the modeling results are compared.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.6
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• pp.309-315
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• 1999

Coupling loss is generated by the time-varying external magnetic field in the normal matrix of the multi-filamentary HTS tape. This paper calculates the coupling loss in the HTS tape. Analytic calculation of the coupling loss cannot consider the effect of the different shapes and the arrangement of the filaments. Numerical calculation by using finite element method and analytic calculation of the coupling loss have been done in this paper and results of two calculations have been compared. Transverse magnetic field and longitudinal magnetic field were considered as the external field.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.89-90
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• 2006

In this paper, the authors propose the RTDS (Real Time Digital Simulator) simulation method which puts a real HTS (High Temperature Superconducting) tape into the simulated voltage feedback system of HTS tape. To perform the RTDS based simulation, the voltage feedback system of HTS tape with hardware is designed and connected to the RTDS. This simulation method is the world first in order to obtain much better for installation of HTS power cable into a utility network.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.890-893
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• 2001

Two-layer self bonding insulating tape consists of butyl rubber(IIR ; Isobutylene-isoprene rubber) adhesive layer and polyethylene protective film. Butyl rubber have inherent characteristics such as resistance to corrosion and water, low temperature flexibility, excellent electrical insulating properties also resistance to environmental effect such as ozone and ultraviolet. Polyethylene film was used for the purpose of good insulating properties and resistance to ozone and ultraviolet. The tape was manufactured using extrusion and calender method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.556-560
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• 2002

The rheological characteristics of PNN-PZT ceramics with high electromechanical coupling factor and electricstrictive constant was investigated. Green sheets of piezoelectric PNN-PZT ceramics were made by tape-casting method with controlling the mixing ratio of a dispersant, an organic binder, and a plasticizer. When the dispersant content was 1 wt.%, the slurry showed the best rheological characteristics for tape casting. The amounts of the plasticizer and the binder was simultaneously varied in the ranges of 1.5~18 and 3~9 wt.%, respectively. When both the plasticizer and binder of 6 wt.% mixed in the solution, respectiveley, the highest green density of the sheet was obtained without macrodefects. Multilyered structures of PNN-PZT/Ag-Pd were successfully fabricated using the optimized tape casting condition. The polarization behavior of these actuators seemed to similar to typical electricstrictive polarization behavior. The multilayer ceramic actuator is about $0.6{\times}10^{-3}$ of strain.