Coated Conductor Wire Research Articles

Electrical Test of Bifilar-Wound Pancake Limiting Module Based on Multi-Stacked Coated Conductor for Application to a Power System

Development of superconducting power equipments is closely related to that of superconducting wires. Recently, continuing from the first generation (1G) BSCCO wire, commercialization of the second generation (2G) wire, coated conductor (CC), is near at hand. Superpower Inc., has already commercialized 2G wire of 600 m piece length. With the development of CC, superconducting power equipments are actively developed and some research groups reported successful demonstration results of the power devices such as cable, fault current limiter, and so on. Since critical current of commercialized coated conductor (CC) of 1.2 mm width is about 250 A at 77 K, methods like stacking or parallel connection that increase operating current are needed. This paper describes fabrication of large current limiting coil and presents electrical test results. The limiting coil was fabricated by assembling 2 modules in parallel; each module was wound by stacking 4 CC wires on a non-inductive pancake bobbin.

Thermal conductivity of 2G HTS wires for current lead applications

We have studied the thermal conductivity of several 2G HTS coated conductor wires produced by AMSC's RABiTSTM/MOD processes. The measurements employed a non-steady state method in which the sample is connected to a cold head on one end and a copper block on the other end. The heat capacity of the copper block is used to determine heat flow through the sample as the cold head slowly warms up. Measurements were done at temperatures ranging from 10 K to 130 K on 2G wires made with a Ni 5at%W substrate and different lamination architectures. The focus of the investigation was on the effects of lamina material type, thickness of the silver layer and alloyed silver. The data show that 2G wires can be 3 times less thermally conductive when compared to 1G BSCCO wires with a Ag-Au matrix, making them excellent candidates for use in current lead applications.

Characteristics of Simultaneous Quenches in Series-Connected YBaCuO Coated Conductors

This paper deals with characteristics of quenches in series-connected YBaCuO coated conductor (CC) samples to gain design parameters of non-inductive superconducting fault current limiter (SFCL). The extremely rapid superconductor-normal transition and inhomogeneous superconducting material cause the uneven quenches in series-connected CC samples. For this experiment, four stabilizer-free CC samples with 200 mm length had been connected in series to investigate the characteristics of quenches and voltage distribution in series-connected CC samples, and the short-circuit test was performed in the case of having shunt resistors of 363 mOmega in parallel with each CC sample and not, respectively. As the result of the experiment, the use of shunt resistors in parallel with CC wires enables to increase in the uniformity of quenching characteristics and parity of voltage distribution. The test results had been compared with the theoretical predictions by using finite element method (FEM).

Nondestructive Investigation of Position Dependent $I_{\rm c}$ Variations in Multi-Meter Coated Conductors

A coated conductor wire produced by the MOD-RABiTS process was nondestructively characterized for I c uniformity along its length. Regions of interest were identified by variations in the I c-n value relationship. These regions were investigated using I c(B,angle) and I c(B||c) measurements. It was found that the conductor properties vary from isotropic to anisotropic over a length of a few centimeters. Additionally, the exponent of the power law fit to the field dependence is shown to vary between 0.84 and 0.67. The position dependence of I c was then measured at two field orientations, H||c and H||ab, along the conductor in a new two measuring stage system. This system allows rapid characterization of a long conductor while providing easily interpreted data on the source of variations.

Progress in research and development on long length coated conductors in Fujikura

This paper describes a process for the fabrication of coated conductor (CC) wires, which is developed by Fujikura, and discusses their properties. These wires are composed of a buffer layer, which is formed by the ion beam assisted deposition (IBAD) technique, and a superconducting layer, which is formed by the pulsed laser deposition (PLD) process. In order to increase the I c × L which means the product of critical current ( I c ) and the length ( L) of the CC wires the I c value and I c distribution along the length of CC wires have been improved by using a new PLD pilot plant. The I c value increases approximately linearly with the thickness of the superconducting layer, and it continues to increase up to a thickness of approximately 4 μm or 5 μm. The I c × L value of our fabricated CC wire is 176,023 Am. The I c value of a short sample is 972 A/cm. The process rate of IBAD is enhanced up to 100 m/h and that of PLD is enhanced up to 20 m/h. A 40-m long CC tape, which has an average I c of 300 A, is fabricated by the improved IBAD and PLD techniques.

Microstructural and superconducting properties of high current metal–organic chemical vapor depositionYBa2Cu3O7−δ coated conductor wires

Metal–organic chemical vapor deposition (MOCVD) on flexible, ion beam assisteddeposition MgO templates has been used to produce high critical current density(Jc) (Y,Sm)1Ba2Cu3Oy (REBCO) films suitable for use in producing practical high temperature superconducting(HTS) coated conductor wires. Thick films on tape were produced with sequential additions of0.7 µm of REBCO via a reel-to-reel progression through a custom-designed MOCVDreactor. Multi-pass processing for thick film deposition is critically dependentupon minimizing surface secondary phase formation. Critical currents(Ics) ofup to 600 A/cm width (t = 2.8 µm, Jc = 2.6 MA cm−2, 77 K, self-field) were obtained in short lengths of HTS wires. Thesehigh performance MOCVD films are characterized by closely spaced(Y,Sm)2O3 nanoparticle layers that may be tilted relative to the film normaland REBCO orientation. Small shifts in the angular dependence ofJc in low and intermediate applied magnetic fields can be associatedwith the tilted nanoparticle layers. Also present in these films wereYCuO2 nanoplates aligned with the YBCO matrix (short dimension perpendicularto the film normal), threading dislocations, and oriented compositedefects (OCDs). The latter structures consist of single or multiplea-axis oriented grains coated on each side with insulating(Y,Sm)2O3 or CuO. The OCDs formed a connected network of insulating phases by the end of thefourth pass. Subsequent attempts at adding additional layers did not increaseIc. There is an inconsistency between the measuredJc and the observed microstructural degradation that occurs with each additional layer,suggesting that previously deposited layers are improving with each repeated reactor pass.These dynamic changes suggest a role for post-processing to optimize superconductingproperties of as-deposited films, addressing issues associated with reproducibility andmanufacturing yield.

Polycrystalline ${\rm MgB}_{2}$ Films on Flexible YSZ Substrates Grown by Hybrid Physical-Chemical Vapor Deposition

We report properties of polycrystalline MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> films deposited on thin flexible yttium-stabilized zirconia (YSZ) substrates by hybrid physical-chemical vapor deposition. The MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> films show a transition temperature of 38.9 K with a narrow superconducting transition (0.1 K). The self-field critical current density in the films reaches 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at low temperatures. These properties do not change after repeated bending over a radius of 10 mm. Low microwave surface resistance comparable to those obtained in epitaxial MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> films on single-crystalline sapphire substrate was observed. The result shows promise of polycrystalline MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> films for applications in superconducting digital circuits as well as in coated conductor wires.

Investigation of YBCO Coated Conductor for Application in Resistive Superconducting Fault Current Limiters

These R&D of YBCO coated conductor wire is progressing very fast. The manufacturing lengths for a single wire have reached up to several hundred meters with high quality. Due to its promising cost predictions, YBCO coated conductor (CC) material might considerably increase the economic feasibility of superconducting power devices (cables, transformers, machines, current limiters and energy storage) in near future. The main requirement for YBCO wire in resistive superconducting fault current limiters (SCFCLs) is quench safety for various short-circuit conditions. Up to now, only a few authors report on this subject. This paper presents experimental quench test results with short and medium length samples of YBCO coated conductor wire for different test conditions. The experimental results confirm the feasibility of YBCO coated conductor wire for application in resistive SCFCLs. Short samples showed fast and effective limitation up to an electric field of 2.7 V/cm for a short-circuit time of 100 ms without material degradation. Even relatively inhomogeneous short samples showed a non-destructive quench. The tests clearly demonstrate that a good contact between the cap layer and the substrate is mandatory to avoid hot spots during quench.

Current limiting characteristics of coated conductors with various stabilizers

Recently, YBCO coated conductor (CC) called as second generation (2G) wire has been developed rapidly. The CC has a stabilizer layer for protecting the wire during a quench of the wire. In resistive superconducting fault current limier (SFCL), the stabilizer makes the resistance and limits the fault current during the fault. Therefore, specification of the stabilizer is one of important design factors in SFCL. This paper describes the current limiting characteristics of three coated conductors with respect to the specifications of the stabilizer. Two samples made by American Superconductors ® have copper stabilizers attached by soldering. However, the two samples have not same structures. One has one-sided stabilizer, the other has both-sided stabilizer. On the other hand, another sample made by IGC-SuperPower ® has copper stabilizer attached by electroplating, and the stabilizer layer surrounds the whole cross-section of the wire. Over-current tests of the three samples with various stabilizers were performed. Each sample has 8 cm in length. From the results, the SFCL using the CC wire could be designed.

Industrial Cu-Ni alloys for HTS coated conductor tape

Copper rich Cu-Ni alloys have been textured with the RABiTS method in order to get non-magnetic and cost efficient substrates for coated conductor wires. The study is focused on two industrial compositions: Cu55Ni45 (Constantan) and Cu70Ni30. Studies on surface roughness have been done. The effects of annealing conditions (temperature and atmosphere) on the grain boundaries deepness were analyzed. Electrolytic polishing was also applied to improve the surface quality. RX pole figures and micro hardness measurements have been achieved on samples annealed up to 950°C. Attention has been paid to the rolling texture and to the annealing processes. The rolling texture has been found to be mainly copper-type (C, S and B contributions). Beginning of recrystallization occurred between 400°C and 600°C and stabilized between 900°C to 950°C, depending on the nickel content of the alloy. Finally both samples, rolled and annealed under the appropriate conditions, have been characterized. Pole figure measurements gave the global in plane and out of plane disorientations of our samples which are in-plane 7.4° and out-plane (RD) 4.3° for both samples. EBSD maps have shown the details of the distribution and have allowed us to quantify the ratio between cubic {100}<001> and twined {122}<21-2> orientations.

Flexible HTS Wires: From Start-Up of a Full-Sized Plant to Industrial Applications

For over a decade high temperature superconducting (HTS) wires have seen a continuous performance increase and have arrived at the level of technical maturity. Among the manufacturers of such wires, Trithor is the only European company that specializes exclusively in HTS wires. To meet the increasing demand for HTS wires, Trithor completed a full-sized manufacturing plant with a design capacity of 2,500 km per year. This paper reports on the plant design. Performance, reliability, quality and cost are of equal importance to the wire user. This paper addresses these areas and presents wire data. Added value in form of high performance insulation, efficient current leads, and coil winding has become available. Performance attributes will be reported in this paper. HTS wire has industrial application throughout the power infrastructure. This paper also provides information on the various prototype applications of Trithor wire. Whereas BSCCO-2223 class multifilamentary composite wire is commercially available now, the YBCO coated conductor wire to be developed by a consortium led by Trithor enables similar or improved performance at further reduced cost. 2G wire will contribute to a widespread use of HTS from 2010 onwards.

Rapid processing method for solution deposited YBa 2Cu 3O 7− δ thin films

YBa 2Cu 3O 7− δ (YBCO) films, deposited on buffered metal substrates, are the primary candidate for second-generation superconducting (SC) wires, with applications including expanded power grid transmission capability, compact motors, and enhanced sensitivity magnetic resonance imaging. Feasibility of manufacturing such superconducting wires is dependent on high processing speed, often a limitation of vapor and solution-based YBCO deposition processes. In this work, YBCO films were fabricated via a new diethanolamine-modified trifluoroacetic film solution deposition method. Modifying the copper chemistry of the YBCO precursor solution with diethanolamine enables a hundredfold decrease in the organic pyrolysis time required for MA/cm 2 current density ( J c) YBCO films, from multiple hours to ∼20 s in atmospheric pressure air. High quality, ∼0.2 μm thick YBCO films with J c (77 K) values ⩾2 MA/cm 2 at 77 K are routinely crystallized from these rapidly pyrolyzed films deposited on LaAlO 3. This process has also enabled J c (77 K)=1.1 MA/cm 2 YBCO films via 90 m/h dip-coating on Oak Ridge National Laboratory RABiTS™ textured metal tape substrates. This new YBCO solution deposition method suggests a route toward inexpensive and commercializable ∼$10/kA m solution deposited YBCO coated conductor wires.

Practical neutral-axis conductor geometries for coated conductor composite wire

To optimize mechanical properties, particularly under bending deformation, a composite laminated architecture is proposed for second generation high temperature superconducting (HTS) coated conductor wire in which the superconductor layer is located at or near the neutral mechanical axis. ‘Neutral-axis’ conductors, each approximately 7 cm long, were fabricated by solder-laminating copper strip onto silver-coated HTS coated conductor strands. ‘Neutral-axis’ and non-laminated samples were bend/reverse-bend tested on mandrels of successively smaller diameters while measuring critical current after each reduction in mandrel size. The ‘neutral-axis’ samples showed significantly improved Ic retention compared to the non-laminated strands.

The status of commercial and developmental HTS wires

This paper provides an update on the development, performance and application of first and second generation high temperature superconductor (HTS) wires fabricated at American Superconductor (AMSC). First generation, multifilamentary composite wire is available commercially today in different viable product forms. This conductor carries 140 × the current of copper of the same cross-section, and is robust enough to stand tough industrial requirements. Second generation HTS wires, having a coated conductor composite architecture, are under development today and achieved substantial progress recently. AMSC’s first generation wire will continue as the workhorse of the industry for the next 3–4 years while AMSC’s second generation coated conductor wire is on track to be reproducible, uniform, scalable, and low cost. This paper provides a product differentiation with a view on the application of HTS wire in the electric power sector. Basic engineering data is reviewed that shall aid the engineer in the selection of the HTS wire product.

High critical current MOD ex situ YBCO films on RABiTS TM and MgO-IBAD templates

Epitaxial YBCO films with a thickness of 0.9 μm have been deposited by ex situ conversion of a trifluoroacetate-based metal organic decomposition precursor on both RABiTS TM (NiW) and MgO-IBAD Hastelloy substrates. These are potential processes for fabricating second generation coated conductor wires. I c values, at 77 K and self-field, as high as 202 and 194 A/cm-width have been achieved on the RABiTS TM and MgO-IBAD samples, respectively.