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The study presents the characteristics analysis of a high-[T.sub.c] persistent current system with double pancake magnet using coated conductor. The voltage generated in the load can be easily used for the determination of the characteristics of the initial current decay.

The study explains the processing variables of the BSCCO-2212 bulk superconductors, which are prepared by a casting process. The analysis reveals that the rods with lower porosities, larger grain sizes and stronger textures exhibit the highest critical current.

Investigating Ni substrates by the powder metallurgy method and evaluated the effects of pressure distribution such as uniaxial pressure and cold isostatic, pressure (CIP) to the compact and the effects of the annealing time on the texturing and microstructure of the substrate is discussed. The development of strong cube texture and high fraction of low angle grain boundaries of Ni-substrates made by powder metallurgy technique is considered useful in the deposition of YBCO coated conductors.

In the study conducted, it shows that the effect of heat treatment condition on the texture development, microstructure, and surface roughness are reported. In the conclusion the sintering condition for the Ni powder compacts is determined by the tensile test for the sintered Ni rods.

Fabricating Ag substrate and evaluated the effects of annealing temperatures on the texture, grain morphology, and surface roughness is investigated. It is concluded that the substrate of strong texture and smooth surface, fabricated in the discussion, is considered suitable for use as a substrate for the epitaxial deposition of superconductor films.

CeO2 buffer layers for YBCO coated conductors are deposited on biaxially textured Ni substrates by a metalorganic chemical vapor deposition (MOCVD) method using a liquid source are investigated. The variables for the texture of CeO2 films were the oxygen partial pressure (P (sub O2)), deposition temperature, and time.

Investigating the NiO buffer layers for YBCO coated conductors by a metal organic chemical vapor deposition (MOCVD) method using a liquid source is presented. It is concluded that the growth rates of the films is much higher by one and two orders of magnitudes than that of the CeO2 film deposited by the PVD methods.

Seed dissolution was observed during top-seeded melt growth of an Yba2Cu3O7-y (Y123) single-domained crystal. The dissolution, which occurred when the seed was in contact with Ba-Cu-O liquid, ended with the resolidification of the dissolved parts during cooling. Upon resolidification to a polycrystal, Y123 evolved into a polycrystalline form. The dissolution behavior of the SMBa2Cu3O7-y (Sm123) is attributed to samarium's solubility in Ba-Cu-O liquid.

A method for producing single-domained Y123 crystals via top-seeded melt growth using two step undercooling has been developed. The technique resulted in a large reduction in the amount of time needed to grow the Y123 single-domained crystal. The two step undercooling process, whose resulting Y123 crystals were subjected to analyses of both microstructure and texture, also exhibited no degradation in the superconducting characteristics of the fabricated superconductors.

We fabricated cube textured Ni substrates for YBCO coated conductors from the initial Specimens prepared by powder metallurgy (P/M) and casting and evaluated the effects of annealing temperature on microstructural evolution and texture formation. To characterize the roles of the two preparation methods, the initial specimens were prepared to be of the same size and experienced the same rolling conditions, and were then annealed in the temperature range of 600° C to 1200° C. The texture was evaluated by X-ray pole-figure analysis and transmission electron microscopy (TEM). The texture analysis indicated that a strong cube texture formed for the substrate made by P/M and this texture did not vary significantly with annealing temperature in the range of 600-1200°C. On the other hand, the texture of the substrate made by casting was more dependent on the annealing temperature, and a twin texture ({221}á221ñ) and several minor texture components began to form at 1000° C. Microstructural observation showed that the morphology of deformation band together with micro-band in the as-rolled tape prepared by P/M was more homogeneous and of higher density than that produced by casting, resulting in a strong cube texture in wider range of annealing temperatures and a finer microstructure after recrystallization. [ABSTRACT FROM AUTHOR]

A 1 MVA single phase high temperature superconducting (HTS) transformer was manufactured and tested. The rated voltage of primary and secondary of HTS transformer are 22.9 kV and 6.6 kV respectively. BSCCO-2223 HTS tape was used for HTS windings of 1 MVA HTS transformer. In order to reduce AC loss generated in the HTS winding, the concentrically arranged winding was adopted to 1 MVA HTS transformer. Single HTS tape for primary windings and 4 parallel HTS tapes for secondary windings were used considering the each rated current of the HTS transformer. A core of HTS transformer was fabricated as a shell type core made of laminated silicon steel plate. And a GFRP cryostat with a room temperature bore was also manufactured. The characteristic tests such as no load test, short circuit test and several insulation tests were performed at 65 K using sub-cooled liquid nitrogen. Through these test results, the validity of design of HIS transformer was ascertained. [ABSTRACT FROM AUTHOR]

AC loss is one of the important parameters in HIS (High Temperature Superconducting) AC devices. Among the HTS AC power devices, the transformer is an essential part in electrical power system. But, AC loss is one of the most serious problems of the HIS transformer, especially with pancake windings, because high alternating magnetic field is applied perpendicularly to the surface of BSCCO wire in HIS windings of that, comparing with the other HTS AC power devices. For the reason above the calculation of AC loss generated in the HTS windings should be carried out in advance when designing the HTS transformer. In the paper we performed study for optimization of winding design to minimize the magnetization loss of HTS winding such as the spaces between pancake windings and operating temperature of HIS wire. The calculation of the AC loss was accomplished by 2-dimensional Finite Element Method. [ABSTRACT FROM AUTHOR]

AC loss is one of the most important parameters in high-temperature superconducting (HTS) ac devices. Among the HTS ac power devices, the transformer is the essential part in the electrical power system. But unfortunately, the transformer is the worst device concerning ac loss because of very large magnetization loss due to high magnetic field applied to the HTS wire. We calculated the magnetization losses in HTS pancake windings for transformer according to the operating temperature. Two kinds of arrangements of HTS pancake windings were adopted for calculation of ac loss of shell-type transformer, and the analysis results were presented and discussed. [ABSTRACT FROM AUTHOR]

We fabricated the textured Ni substrate and evaluated the effects of processing variables on microstructural evolution and texture transformation. Ni-rods as an initial specimen were prepared by two different methods, i.e., powder metallurgy (PIM) and plasma arc melting (PAM). To evaluate the effect of two preparation methods, the initial specimens were prepared to be of same size and experienced by same rolling conditions. The texture of the substrate was characterized by pole-figure and surface condition was evaluated by atomic force microscopy. It was observed that the texture of substrate made by PIM did not significantly varied with annealing temperature of 800 ∼ 1200°C and the full-width at half-maximums (FWHM) of both in-plane and out-of-plane were 9° ∼ 10°. On the other hand, the texture of substrate made by PAM was more dependent on the annealing temperature and the FWHM of in-plane texture was 9° ∼ 13° at the temperature range. In addition, twin texture, (221) (221), was formed as the temperature increased further. OM micrographs showed that the grain size of substrate made by P/M was smaller than that made by PAM and this difference was correlated to the microstructure of initial specimens. [ABSTRACT FROM AUTHOR]

A 1 MVA single phase high temperature superconducting (HTS) transformer was fabricated and a part of experimental test for characteristics of the transformer was performed. The rated voltages of primary and secondary of the HTS transformer are 22.9 kV and 6.6 kV respectively. BSCCO-2223 wire was used for HTS windings whose shapes are double pancake arranged reciprocally. Single HTS wire for primary windings and 4 HTS wires for secondary windings were used considering the rated current of the transformer. Four HTS wires in secondary windings were transposed at the connection between double pancakes 3 times. The electrical insulation and transport current test were performed at 77 K using liquid nitrogen. The rest of the test for the characteristics of the transformer is in progress. [ABSTRACT FROM AUTHOR]

CeO[sub 2] buffer layers for YBa[sub 2] Cu[sub 3]O[sub 7](YBCO) coated conductors were deposited on biaxially textured Ni substrates by metalorganic chemical vapor deposition (MOCVD) method. The variables were the oxygen partial pressure (P[sub O2]), deposition temperature and time. The (200) texture of CeO[sub 2] was formed at T = 500°C-520 °C, t = 3-15 min and P[sub O2] = 2.30 torr, while the (111) and (200) texture were competitively formed at other condition. The surface roughness of CeO[sub 2] films was as good as 5-15 nm up to 500 °C, while it rapidly increased as a result of grain growth of the CeO[sub 2] at T ≥ 520 °C. The surface roughness of the CeO[sub 2] films also increased as the deposition time increased. The growth rate of the CeO[sub 2] films at T = 520 °C and P[sub O2] = 2.30 torr was 200 nm/min, which is much higher than those prepared by other physical deposition methods. [ABSTRACT FROM AUTHOR]

It is common practice to wind coils in pancake shape for conventional high voltage transformers because of electrical insulation problems. In HTS superconducting transformers, the perpendicular component of magnetic flux density (B[sub r]) applied to HTS tapes of pancake windings becomes larger than that of solenoid winding, thereby decreasing the critical current in the HTS tapes. This paper introduces several methods to reduce B[sub r] applied to the HTS tapes in the transformer with double pancake windings by changing winding arrangements and the relative permeability of flux diverters. We have conducted a winding design for a single-phase 1 MVA 22.9 kV/6.6 kV HTS transformer. The magnetic field in the spaces occupied by the windings and its vicinity was numerically simulated. We observed a change of B[sub r] due to various gap arrangements of high voltage and low voltage windings and various reciprocal arrangements. We also observed a change of B[sub r] on the HTS tapes due to variation of relative permeability of flux diverters placed between the high voltage winding and the low voltage winding. [ABSTRACT FROM AUTHOR]

Examines interface irregularity and texture evolution of Bi-Sr-Ca-Cu-O superconducting tape processed by the powder-in-tube method. Core diameter and thickness; Improvement in the degree of texture of BSCCO grains during the rolling and drawing processes; Combined effects of interface irregularity and degree of texture on the critical current of the tape.

Studies the preparation of oxide buffers on a cube-textured Ni substrate for coated superconductors by metal organic chemical vapor deposition (MOCVD). Presentation of a schematic diagram of the belt-driven precursor feeding system and MOCVD reactor; Intensity ratio of CeO2 film with deposition temperature.

The melt processed Y123 oxide superconductor shows a very high magnetic levitation force and there is lots of research to develop its application technology such as a fly wheel energy storage device. Our recent study on the microstructure of the melt-processed samples showed that oxygenation condition significantly affected the magnetic properties of the YBCO sample. We examined the microstructure around the Y211 inclusion trapped within the melt-textured domain to understand the formation mechanism of the defects such as CuO stacking faults, dislocations and BaCuO platelet boundaries. The microstructures of the YBCO samples were heat-treated in flowing oxygen for various times. No defects were observed around the trapped Y211 inclusions and in the Y123 matrix of the tetragonal sample. Meanwhile, dislocation, transformation twins, the CuO stacking fault and BaCuO platelet structure were observed in the sample transformed into superconducting orthorhombic phase by low temperature heat treatment. The CuO stacking fault and BaCuO platelet structure are developed along the [100] and [010] direction on the a-b plane of the orthorhombic Y123. The formation mechanism of the defects was discussed on the basis of the oxygenation-induced decomposition mechanism. [ABSTRACT FROM PUBLISHER]

YBCO thin films were prepared on LaA1O3 (100) single-crystal substrates using the metalaorganic deposition of trifluoroacetates (TFA-MOD). Unlike the normal TFA-MOD process, TFA based solutions were prepared dissolving YBCO powder into the trifluoroacetic acid solvent. The solutions were coated on the substrates by spin coating, fired at the temperature up to 400°C in 4.2% humid and oxygen atmosphere, fired again at the temperature region of 725-850°C for 2 h in 4.2% humidity and 1000 ppm oxygen partial pressure, and finally Oxygenated at 450 °C for 1 h. Similar to the normal TFA-MOD process, both microstructure and superconducting properties of YBCO films were highly sensitive to the firing temperature. Optimally processed YBCO films of ∼250 nm thickness exhibited TC,zero of 90 K and JC of 2.9 MA/cm² at 77 K in a self-field. The present results clearly evidence that our cost-effective modified TFA-MOD process is applicable to the fabrication of YBCO coated conductors. [ABSTRACT FROM AUTHOR]