• Progress in Superconductivity and Cryogenics
• /
• v.7 no.4
• /
• pp.20-23
• /
• 2005

The Resistive Type High Temperature Superconducting Fault Current Limiter (SFCL) has been developed in many countries. Until now, materials of the resistive SFCL were Bi2212 bulk and YBCO thin film. Although YBCO coated conductor (CC) has many advantages such as high n-value and critical current for applying resistive SFCL, the resistive SFCL using CC doesn't have developed yet. The bifilar winding type SFCL was manufactured and tested rated on 30V/80A. In normal state, the SFCL using pancake type bifilar winding had very low impedance. When a fault occurred, the SFCL limited the fault current efficiently. Through these results of experiment, large-scale SFCL using CC should be developed in the future.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.07a
• /
• pp.527-530
• /
• 2002

A lot of efforts have been focused on the optimization of PIT parameters for Bi-2223/Ag wire. In this paper, initial annealing of Bi-2223/Ag wire to transform Bi-2212 orthorhombic from Bi-2212 tetragonal Precursor was investigated. This initial annealing step at low oxygen partial pressure were to transform Bi-2212 orthorhombic structure and to reduce the formation of second phases at superconducting wire. However Bi-2223 Phases were appeared at higher annealing temperature. Critical currents(Je) of Bi-2223/Ag tapes were sintered at low oxygen Partial pressure were higher than that of the wires sintered at atmosphere condition. In order to investigate the effect of rolling reduction ratio, Bi-2223/Ag HTS tapes were rolled with different reduction ratio. There were no clear difference of Je and filaments shape with various rolling reduction ratio.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.11b
• /
• pp.288-291
• /
• 2001

It is very important to select suspension solution for forming electrophoretic deposited YBCO thick mm, because it is heavily affected to its superconducting properties. In this paper, high-temperature superconductor films of $YBa_{2}Cu_{3}O_{7-x}$ were fabricated by electrophoretic deposition (EPD) from alcohol-based suspension such as iso-propanol, iso-butanol, and their mixture. For the formation of YBCO dense and adherent coating on a silver wire by EPD, 1 % PEG(1000) 2 ml, as a additive for making their surface crack-free, was used for electrophoresis. As a results, the cracks were considerably decreased and the superconducting critical current density $(J_e)$ without/with PEG was $1200A/cm^2$ and $2020A/cm^2$, which films deposited in mix iso-propanol and iso-butanol suspension.

• Journal of the Korean institute of surface engineering
• /
• v.24 no.2
• /
• pp.67-72
• /
• 1991

The feasibility of preparing superconducting $Y_1Ba_2Cu_3O_y$ films on metallic substrate was exmined in an attempt to fabricate a tape conductor. Deposition methods employed were sputtering, laser ablation, and plasma flash evaporation. Although zero resistance temperature (Tc) is achieved above 90 K, critical current density values (Jc) obtained so far is still low as compared with those reported in the films grown on single crystal substrates. This may be caused by the misalignment of the crystal structure of the films on metal substrates. A further improvement if Jc for highly-oriented polycrystalling films is being investigated at the present time.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1999.05a
• /
• pp.65-68
• /
• 1999

A well oriented Bi2212 superconductor thick films were fabricated by screen printing with a Cu-free Bi-Sr-Ca-O mixture powder on a copper plate and heat-treating at 820-88$0^{\circ}C$ for several minute in air. During the heat-treatment, the printing layer partially melted by reaction between the Cu-free precursor and CuO of the oxidizing copper plate. In the partial melting state, it is believed that the solid phase is Bi-free phase and Cu-rich phase and the composition of the liquid is around Bi : Sr : Ca : Cu = 2 : 2 : 0 : 1. Following the partial melting, the Bi2212 superconducting phase is formed at Bi-free phase/liquid interface by nucleation and grows. With decreasing the Bi composition in the precursor powder, the critical temperature(T$_{c}$) of the fabricated Bi2212 thick film increased to about 79 K.K.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.11a
• /
• pp.288-291
• /
• 2001

It is very important to select suspension solution for forming electrophoretic deposited YBCO thick film, because it is heavily affected to its superconducting properties. In this paper, high-temperature superconductor films of YBa$_2$Cu$_3$$O_{7-x}$ were fabricated by electrophoretic deposition (EPD) from alcohol-based suspension such as iso-propanol, iso-butanol, and their mixture. For the formation of YBCO dense and adherent coating on a silver wire by EPD, 1% PEG(1000) 2 $m\ell$, as a additive for making their surface crack-free, was used for electrophoresis. As a results, the cracks were considerably decreased and the superconducting critical current density (J$_{c}$) without/with PEG was 1200 A/$\textrm{cm}^2$ and 2020 A/$\textrm{cm}^2$, which films deposited in mix ism-propanol and iso-butanol suspension.ion.

• KEPCO Journal on Electric Power and Energy
• /
• v.1 no.1
• /
• pp.157-162
• /
• 2015

Large scale superconducting magnetic energy storage (SMES) system requires very high magnetic energy density in its superconducting coils to enhance the energy capacity and efficiency of the system. The recent high temperature superconducting (HTS) conductors, so called 2G conductors, show very good performance under very high magnetic field so that they seem to be perfect materials for the large scale SMES coils. A general shape of the coil system with the 2G HTS conductor has been a tor oid, because the magnetic field applied perpendicularly to the surface of the 2G HTS conductor could be minimized in this shape of coil. However, a toroid coil requires a 3-dimensional computation to acquire the characteristics of its critical current density - magnetic field relations which needs very complicated numerical calculation, very high computer specification, and long calculation time. In this paper, we suggested an analytic and statistical calculation method to acquire the maximum magnetic flux density applied perpendicularly to the surface of the 2G HTS conductor and the stored energy in the toroid coil system. Although the result with this method includes some errors but we could reduce these errors within 5 percent to get a reasonable estimation of the important parameters for design process of the HTS toroid coil system. As a result, the calculation time by the suggested method could be reduced to 0.1 percent of that by the 3-dimensional numerical calculation.

• Progress in Superconductivity and Cryogenics
• /
• v.4 no.1
• /
• pp.45-59
• /
• 2002

Evaluation of the mechanical properties of Bi-2223/Ag HTS tapes was carried out by the tension and bending tests. Most of the Bi-2223/Ag tapes retained critical current up to 10 kgf/mm$_2$ axial tension stress, and 0.2% tension strain at room temperature. Applied tension strain exceeding 0.3% in superconducting tapes at 77 K leaded to rapid degradation of the critical current. It was observed that the more filaments, the better axial tension property at 77 K, self-field The influence of bending strain on critical current degradation was revealed to be less sensitive for Bi-2223/Ag HTS tapes with a more number of filaments and higher silver ratio.

• Progress in Superconductivity and Cryogenics
• /
• v.13 no.4
• /
• pp.26-29
• /
• 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
• /
• v.6 no.4
• /
• pp.51-54
• /
• 2004

A 1 MV A single phase high temperature superconducting (HTS) transformer was manufactured. In order to reduce AC loss generated in the HTS winding, winding was concentrically arranged. Operation temperature is set at 65K to increase the critical current and reduce the amount of HTS tape usage and the volume. The cryogenic system which consists of main cryostat with the windings and secondary cryostat with 2 GM coolers and cryopump on top and heat exchanger inside is also designed and the cooling performance is simulated with Fluent. Temperature distribution of the windings is investigated whether the windings are kept under designed operation temperature.