S. Fleshler

Progress in high temperature superconductor coated conductors and their applications

Second generation (2G) high temperature superconductor (HTS) wires are based on a coated conductor technology. They follow on from a first generation (1G) HTS wire consisting of a composite multifilamentary wire architecture. During the last couple of years, rapid progress has been made in the development of 2G HTS wire, which is now displacing 1G HTS wire for most if not all applications. The engineering critical current density of these wires matches or exceeds that of 1G wire, and the mechanical properties are also superior. Scale-up of manufacturing is proceeding rapidly, with several companies already supplying the order of 10 km annually for test and demonstration. Coils of increasing sophistication are being demonstrated. One especially attractive application, that relies on the specific properties of 2G HTS wire, is fault current limitation. By incorporating a high resistivity stabilizer in the coated conductor, one can achieve high resistance in a quenched state during a fault event and at the same time provide significant heat capacity to limit the temperature rise. A test of a 2.25 MVA single phase system at 7.5 kV employing such wire by the Siemens/AMSC team has demonstrated all the key features required for a cost-effective commercial system. A novel approach to providing fault current limiting functionality in HTS cables has also been introduced.

Advances in second generation high temperature superconducting wire manufacturing and R&D at American Superconductor Corporation

The RABiTS?/MOD-YBCO (rolling assisted biaxially textured substrate/metal?organic deposition of YBa2Cu3O7??) route has been established as a low-cost manufacturing process for producing high performance second generation (2G) wire. American Superconductor Corporation (AMSC) has used this approach to establish a production scale manufacturing line based on a wide-web manufacturing process. This initial production line is currently capable of producing 2G wire in lengths to 500?m with critical currents exceeding 250? A?cmwidth?1 at 77?K, in the self-field. The wide-web process, combined with slitting and lamination processes, allows customization of the 2G wire width and stabilizer composition to meet application specific wire requirements. The production line is currently supplying 2G wire for multiple cable, fault current limiter and coil applications. Ongoing R&D is focused on the development of thicker YBCO layers and improved flux pinning centers. This paper reviews the history of 2G wire development at AMSC, summarizes the current capability of the 2G wire manufacturing at AMSC, and describes future R&D improvements.

HTS wire at commercial performance levels

Short rolled multifilamentary BSCCO-2223 oxide-powder-in-tube (OPIT) wire has reached a core critical current density J/sub c/ over 73,000 A/cm/sup 2/ (77 K, self-field, 1 /spl mu/V/cm) in multiple samples, with engineering (full-cross-section) current density J/sub c/ of 22,800 A/cm/sup 2/ (77 K, self-field, 1 /spl mu/V/cm). Regular production wires several hundred meters long show average engineering current density over 10,000 A/cm/sup 2/ (77 K, self-field, 1 /spl mu/V/cm), a benchmark for commercial electric power applications such as cables and motors. Cost studies indicate that cost-performance below

HTS Wire: status and prospects

10/kA-m is attainable for full-scale production levels, Next-generation YBCO-123 coated conductor technology offers further potential cost-performance improvements.

Measurement of the ac power loss of (Bi,Pb)2Sr2Ca2Cu3Ox composite tapes using the transport technique

Abstract Practical, robust high temperature superconducting (HTS) wire is a composite of high temperature superconductor and metal. The composite provides many advantages, including improved mechanical properties and stability. Multi-filamentary composite fabricated with the BSCCO HTS material has achieved performance for commercial applications, and commercial price/performance is on the near horizon. This wire enables HTS applications such as power cables, marine propulsion motors, utility generators and magnets for materials processing. Coated conductor is also a composite, combining the YBCO HTS material with a metal or metal-alloy substrate; this technology is in the stage of research and development. The status and commercial prospects of these wire technologies are reviewed.

Stability of bare and copper-laminated YBCO samples: experimental & simulation results

The transport self‐field ac loss voltages of (Bi,Pb)2Sr2Ca2Cu3Ox (Bi‐2223) multifilamentary tapes depend strongly on the voltage lead configuration. We have measured the loss voltage as a function of the measuring circuit loop size defined by the voltage leads and the tapes for well‐defined lead geometries. The loss signal was found to reach a limiting value when the length of the loop transverse to the tape was several times the tape width. This limiting voltage represents the ‘‘true’’ self‐field ac loss as predicted by new theoretical analysis.

Industrial high temperature superconductors: perspectives and milestones

In this study of stability of YBCO composite, we investigate quench/recovery behavior of YBCO test samples, bare and copper-laminated, by subjecting each test sample, immersed in a bath of liquid nitrogen boiling at 77.3 K, to a transport current pulse superimposed to a baseline DC current of 90-95% the critical current. The current pulse has an amplitude up to /spl sim/4.5 times the critical current and a duration of 300 ms. This paper presents both experimental and simulation results showing that composite YBCO tape that incorporates a copper lamina stabilizes and to a degree protects the conductor against large over-current pulses.

Rapid doubling of the critical current of YBa2Cu3O7-δ coated conductors for viable high-speed industrial processing

High Temperature Superconductors (HTS) are widely considered for large power applications used by industrial end-users and electric utilities. The prominent application areas include power transmission cables, electric motors, generators, current limiters, and transformers. The promising design concepts rely on HTS to be a flexible composite conductor, robust enough to handle an industrial environment. Currently, the most advanced manufacturing method for flexible composite conductor is the Bi-2223-OPIT, used by many organizations. Significant advances in HTS technology have been made, with average critical current performance above 115 A at 77 K which is equivalent to an engineering current density of 13.8 kA/cm/sup 2/. During the past 18 months, American Superconductor increased its HTS wire manufacturing capacity from 250 km to 500 km per year to meet the increased demand for development and demonstrations. While this level of quality and quantity enables impressive demonstrations of prototype power applications, it does not fully meet the requirements of commercial economic viability. Therefore, to further decrease wire price to

Progress in Bi-2223 tape performance

50/kA-m, American Superconductor is currently siting a new facility dedicated to the manufacturing of Bi-OPIT-2223 wire in quantities of 10000 km per year. Initial applications for this wire are power transmission cables, industrial motors and electrical generators. This paper will report on the performance and reliability testing of Bi-2223 tapes. We will discuss the electrical, tensile, compression, and fatigue testing results of tapes manufactured for specific key projects. Also, we will review mass availability of High Temperature Superconductors and we will report on technological and price/performance limitations to be overcome to increase the applicability of HTS in research and industrial devices and equipment.

Fatigue of a Reinforced High Temperature Superconducting Tape

We demonstrate that 3.5-MeV oxygen irradiation can markedly enhance the in-field critical current of commercial second generation superconducting tapes with an exposure time of just 1 s per 0.8 cm2. The speed demonstrated here is now at the level required for an industrial reel-to-reel post-processing. The irradiation is made on production line samples through the protective silver coating and does not require any modification of the growth process. From TEM imaging, we identify small clusters as the main source of increased vortex pinning.