American Superconductor Corporation

Other

American Semiconductor Corporation

American Superconductor Corpration

Abb Technology Ag

Craig J Christopherson

Gilbert N Riley, Jr

Alexander Otto

Gregory L Snitchler

Qi Li

Eric R Podtburg

Peter R Roberts

Kenneth L DeMoranville

Alexis P Malozemoff

Jeffrey M Seuntjens

Ralph P Mason

Peter D Antaya

William L Carter

Swarn S Kalsi

Martin Lakner

Willi Paul

John D Scudiere

Lawrence J Masur

Christopher A Craven

Dietrich Bonmann

Steven Fleshler

William L Barnes

Harry Zueger

Bruce R Bent

William J Michels

Jeffrey Michael Seuntjens

Derek Patrick Daly

Steven Hancock

Sy-Jenq Loong

Robert C Diehl

Jennifer H Garrant

Thomas De Santos

Deborah L Ouellette

David M Olen

Gilber N Riley

An elongated current limiting composite material comprising one or more high-temperature superconductor filaments and a second electrically conductive member, which may include a sheath of high bulk resistivity surrounding the filament. The current limiter exhibits dissipation in the range of 0.05-0.5 V/cm at currents of 3-10 times the operating current, thereby minimizing fault currents and improving recovery capability.

Current limiting composite material

An oxide superconducting cable is provided having a plurality of strands comprised of at least one oxide superconductor filament sheathed in a ductile and conductive metal matrix and least one of said strand further comprising a substantially continuous high resistivity coating substantially surrounding said at least one strand. The strands are positioned and arranged to form a cable. The cable is prepared by (a) applying a ductile predecessor coating to a plurality of strands, each said strand comprised of at least one oxide superconductor filament or a precursor thereto sheathed in a ductile metal matrix, and the ductile predecessor capable of conversion into a high resistivity material; (b) assembling the plurality of strands into a cable; and (c ) converting the ductile predecessor into a high resistivity material, where steps (a) and (b) can be performed in any order.

Decoupling of superconducting elements in high temperature superconducting composites

The invention provides a multifilamentary superconducting composite article comprising multiple substantially electrically decoupled domains, each including one or more fine, preferably twisted filaments of a desired superconducting oxide material. In a preferred embodiment, the article comprises a matrix, which substantially comprises a noble metal, a conductive jacketing layer surrounding the matrix, a plurality of discrete filament decoupling layers, each comprising an insulating material, disposed within the matrix to separate the matrix into a plurality of substantially electrically decoupled domains; a plurality of filaments, each comprising a desired superconducting oxide, which are disposed within and essentially encapsulated by the matrix and chemically isolated thereby from the decoupling layers, each of the electrically decoupled domains containing at least one filament. It provides multifilamentary articles that exhibit high DC performance characteristics and AC performance markedly superior to any currently available for these materials. A process and intermediate for making the article are also provided. The article may be manufactured by first, forming a composite intermediate comprising multiple domains, each including one or more fine, preferably twisted filaments of a superconducting oxide or its precursors and then thermomechanically processing the intermediate at conditions sufficient to produce at least one of the effects of texturing, crack healing and, if a precursor to the desired superconducting oxide remains, phase transformation in the filament material under conditions which support the electrical separation of the domains. Preferably, the forming step includes the step of providing filament decoupling layers comprising insulating materials or their predecessors to provide the desired domain separation and most preferably, the insulating material is formed in situ from its predecessor during the thermomechanical processing step. Oxide-forming predecessors are preferred, especially oxide forming materials selected from the group consisting of the transition metals, the alkaline earths, titanium, zirconium, niobium, molybdenum, aluminum, and their alloys. In a preferred embodiment, the desired superconducting oxide material is a member of the bismuth or yttrium families of oxide superconductors.

Structure and method of manufacture for minimizing filament coupling losses in superconducting oxide composite articles

A multifilamentary superconductor composite having a high fill factor is formed from a plurality of stacked monofilament precursor elements, each of which includes a low density superconductor precursor monofilament. The precursor elements all have substantially the same dimensions and characteristics, and are stacked in a rectilinear configuration and consolidated to provide a multifilamentary precursor composite. The composite is thereafter thermomechanically processed to provide a superconductor composite in which each monofilament is less than about 50 microns thick.

Fine uniform filament superconductors

A method of texturing a multifilamentary article having filaments comprising a desired oxide superconductor or its precursors by torsionally deforming the article is provided. The texturing is induced by applying a torsional strain which is at least about 0.3 and preferably at least about 0.6 at the surface of the article, but less than the strain which would cause failure of the composite. High performance multifilamentary superconducting composite articles having a plurality of low aspect ratio, twisted filaments with substantially uniform twist pitches in the range of about 1.00 inch to 0.01 inch (25 to 0.25 mm), each comprising a textured desired superconducting oxide material, may be obtained using this texturing method. If tighter twist pitches are desired, the article may be heat treated or annealed and the strain repeated as many times as necessary to obtain the desired twist pitch. It is preferred that the total strain applied per step should be sufficient to provide a twist pitch tighter than 5 times the diameter of the article, and twist pitches in the range of 1 to 5 times the diameter of the article are most preferred. The process may be used to make a high performance multifilamentary superconducting article, having a plurality of twisted filaments, wherein the degree of texturing varies substantially in proportion to the radial distance from the center of the article cross-section, and is substantially radially homogeneous at any given cross-section of the article. Round wires and other low aspect ratio multifilamentary articles are preferred forms. The invention is not dependent on the melting characteristics of the desired superconducting oxide. Desired oxide superconductors or precursors with micaceous or semi-micaceous structures are preferred. When used in connection with desired superconducting oxides which melt irreversibly, it provides multifilamentary articles that exhibit high DC performance characteristics and AC performance markedly superior to any currently available for these materials. In a preferred embodiment, the desired superconducting oxide material is BSCCO 2223.

Torsional texturing of superconducting oxide composite articles

Methods of treating superconducting composites to enhance their wettability in solder, and composites having enhanced wettability. It has been found that wettability can be substantially enhanced by stripping a thin layer off the surface of the composite before incorporating it into a laminated component. This layer can be stripped, for example, by chemically etching the composite, for example in a solution of nitric acid and ammonium bifluoride.

Composites having high wettability

A low-aspect ratio multi-filament superconductor wire includes a plurality of oxide superconductor filaments arranged in an elongated wire structure. Each filament of the wire also has a low-aspect ratio. The filaments are textured such that a crystallographic c direction of each filament is aligned with a crystallographic c direction of all other filaments with the crystallographic c directions being perpendicular to the longitudinal axis of the wire structure. The invention also features a groove rolling machine for forming a low-aspect ratio multi-filament superconductor wire by texturing a precursor tape by deforming the tape to a low-aspect ratio wire by reducing a larger dimension of the tape in such a way as to prevent buckling of the tape. A superconducting cable can be formed by planetary winding a plurality of multi-filament superconductor wires.

Low-aspect ratio superconductor wire

The combination of one or more high reduction drafts with controlled, low back tensions increases the range of deformation conditions over which dimensional tolerances and J,may be optimized. The method comprises the steps of: first, providing a precursor article comprising a metal matrix surrounding a plurality of filaments extending along the length of the article and comprising precursors to a desired superconducting ceramic; next, roll working the precursor article during a breakdown stage at a back tension less than the elastic to plastic transition threshold of the composite during at least one high reduction roll working draft, and, then, sintering the rolled article to obtain the desired superconducting ceramic. In a preferred embodiment, the rolling step further comprises rolling the article at a front tension less than the elastic to plastic transition threshold of the rolled, unsintered article.

Tensioning process for manufacture of superconducting ceramic composite conductors

A superconducting article having a high bulk sheath resistivity, and methods of manufacture of such an article. High-temperature superconductor filaments are disposed in a ductile matrix comprising a high silver content. The matrix is then coated with a solute and heated to a temperature high enough to allow the solute to diffuse into the matrix, but not high enough to allow substantive degradation or poisoning of the superconductor. After diffusion and cooling, the matrix comprises a silver alloy having a higher bulk resistivity than the pure silver.

Superconducting composite with high sheath resistivity

A multifilamentary superconducting composite article comprising multiple substantially electrically decoupled domains, each including one or more fine, preferably twisted filaments of a desired superconducting oxide material. In a preferred embodiment, the article comprises a matrix, which substantially comprises a noble metal, a conductive jacketing layer surrounding the matrix, a plurality of discrete filament decoupling layers, each comprising an insulating material, disposed within the matrix to separate the matrix into a plurality of substantially electrically decoupled domains; a plurality of filaments, each comprising a desired superconducting oxide, which are disposed within and essentially encapsulated by the matrix and chemically isolated thereby from the decoupling layers, each of the electrically decoupled domains containing at least one filament. It provides multifilamentary articles that exhibit high DC performance characteristics and AC performance markedly superior to any currently available for these materials. The article may be manufactured by first, forming a composite intermediate comprising multiple domains, each including one or more fine, preferably twisted filaments of a superconducting oxide or its precursors and then thermomechanically processing the intermediate at conditions sufficient to produce at least one of the effects of texturing, crack healing and, if a precursor to the desired superconducting oxide remains, phase transformation in the filament material under conditions which support the electrical separation of the domains. Preferably, the forming step includes the step of providing filament decoupling layers comprising insulating materials or their predecessors to provide the desired domain separation and most preferably, the insulating material is formed in situ from its predecessor during the thermomechanical processing step. Oxide-forming predecessors are preferred, especially oxide forming materials selected from the group consisting of the transition metals, the alkaline earths, titanium, zirconium, niobium, molybdenum, aluminum, and their alloys. In a preferred embodiment, the desired superconducting oxide material is a member of the bismuth or yttrium families of oxide superconductors.

Structure and method of manufacture for minimizing filament coupling

A method of forming a textured superconductor wire includes constraining an elongated superconductor precursor between two constraining elongated members placed in contact therewith on opposite sides of the superconductor precursor, and passing the superconductor precursor with the two constraining members through flat rolls to form the textured superconductor wire. The method includes selecting desired cross-sectional shape and size constraining members to control the width of the formed superconductor wire. A textured superconductor wire formed by the method of the invention has regular-shaped, curved sides and is free of flashing. A rolling assembly for single-pass rolling of the elongated precursor superconductor includes two rolls, two constraining members, and a fixture for feeding the precursor superconductor and the constraining members between the rolls. In alternate embodiments of the invention, the rolls can have machined regions which will contact only the elongated constraining members and affect the lateral deformation and movement of those members during the rolling process.

Method of texturing a superconductive oxide precursor

The invention relates to a processing method for fabricating a superconducting magnetic coil using a mandrel having a consumable component. When exposed to a final processing step, the consumable component is mechanically weakened through oxidation or thermal decomposition. The mandrel can then be easily removed from the coil without straining the conductor, thus preserving the coil's electrical and mechanical properties.

Consumable mandrel for superconducting magnetic coils

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Worcester, MA, United States of America

Craig J Christopherson