Superconductor technology: apparatus – material – process – High temperature devices – systems – apparatus – com- ponents,... – Superconducting wire – tape – cable – or fiber – per se
Reexamination Certificate
1999-09-23
2001-05-08
Talbot, Brian K. (Department: 1762)
Superconductor technology: apparatus, material, process
High temperature devices, systems, apparatus, com- ponents,...
Superconducting wire, tape, cable, or fiber, per se
C505S232000, C505S236000, C505S237000, C505S704000, C428S930000
Reexamination Certificate
active
06230033
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to superconducting ceramic tapes, and particularly to laminated superconducting ceramic tapes.
When a superconductor tape is put under tension the ceramic grains in the tape degrade resulting in a decrease in the critical current carrying capacity of the superconductor tape. To address this issue, it has been known to form superconductors by laminating the superconductor tape which may be a previously compressively strained tape to a support structure having a thermal expansion coefficient larger than that of the superconducting tape to improve the tape's tolerance to tensile and bending stresses.
SUMMARY OF THE INVENTION
A superconducting ceramic formed by laminating a superconducting ceramic tape to a tensioned laminate results in a superconducting ceramic tape that is under compression and enables higher level of tensile strain to be applied to the superconductor during use without causing degradation of the tapes critical current carrying capacity.
The invention relates to a superconducting ceramic including a laminate and a superconducting ceramic tape joined to the laminate. The laminate and superconductor tape are joined such that the tape is under a compressive stress. The compressive stress is of a greater amount than the compressive stress which results from differences in thermal expansion of the tape and the laminate.
In particular embodiment of the invention, the superconductor tape is under a compressive stress in the range of about 10 to 150 MPa, preferably about 30 to 120 MPa, and most preferably about 60 to 120 MPa. The laminate is a tape formed from stainless steel, copper, copper alloys, or superalloys. Solder or epoxy can be used for joining the superconductor tape to the laminate. A first side of the superconductor tape can be joined to one laminate and a second side of the superconductor tape can be joined to a second laminate.
According to another aspect of the invention, a superconducting ceramic includes a laminate and a superconducting ceramic tape joined to the laminate such that the tape is under compression. The superconducting ceramic can withstand tensile strains in a single bend test of at least 1.5% without degrading current carrying capability of the tape more than 10%, that is below 90% of its unbent value. In another aspect, the superconducting ceramic can withstand tensile strains in a tension test of at least 0.5% and preferably 0.6without degrading current carrying capability of the tape more than 10%, that is below 90% of its unbent value.
According to additional aspects of the invention, a superconducting coil and a cable conductor are formed from the superconducting ceramic of the invention.
According to yet another aspect of the invention, a superconducting ceramic is formed by joining a superconducting ceramic tape to a laminate. The laminate is at a greater tension than the superconductor tape during joining.
According to another aspect of the invention, an apparatus for laminating a superconducting ceramic tape to a laminate includes a laminator and a feed guide for guiding the superconducting ceramic tape and the laminate along a laminate process path into the laminator. Throughout the laminating process, the radius of curvature of the superconducting ceramic tape is maintained at greater than about 3 inches.
In particular embodiments of the invention, the laminate has a coefficient of thermal expansion greater than that of the superconducting ceramic tape. A heater enables lamination at a predetermined elevated temperature and a cooler cools the superconducting ceramic tape and the laminate thereby placing the tape under compression.
A laminate payoff roll and a superconducting ceramic tape payoff roll are located at an upstream end of the laminate process path. A brake is associated with the laminate payoff roll for tensioning the laminate. A take-up roll including a motor is located at a downstream end of the laminate process path. A second brake is associated with the superconducting ceramic tape payoff roll for independently tensioning the tape. In another aspect of the invention, a second laminate payoff roll including a third brake is located at the upstream end of the laminate process path. The laminates are tensioned at a higher tension than the superconducting tape and the superconducting tape is laminated between the two laminates.
According to another aspect of the invention, an apparatus for laminating a superconducting ceramic tape to a laminate includes a laminator and a feed guide for guiding the superconducting ceramic tape and the laminate along a substantially straight laminate process path into the laminator.
According to yet another aspect of the invention, a method of laminating a superconducting ceramic tape includes. the steps of feeding the superconducting ceramic tape through a laminator while maintaining a radius of curvature of the superconducting ceramic tape greater than about 3 inches; feeding a laminate into the laminator; and laminating the superconducting ceramic tape to the laminate.
In particular embodiments of the method of the invention. the tape and the laminate are heated during lamination to expand the tape and the laminate. The tape and the laminate are cooled after lamination to put the tape under compression. The laminate is tensioned prior to lamination. A second laminate is fed into the laminator and the superconducting ceramic tape is laminated to the second laminate.
According to another aspect of the invention, a method of laminating a superconducting ceramic tape includes feeding the superconducting ceramic tape through a laminator along a substantially straight path, feeding a laminate into the laminator, and laminating the superconducting ceramic tape to the laminate.
Advantages of the system may include one or more of following. The superconducting ceramic tape is not subject to strains during lamination that would result in degradation of the tape's critical current carrying capacity. Tensions placed on the laminates and on the superconducting ceramic tape are independently controllable to enable a larger tension to be placed on the laminates than on the superconducting ceramic tape.
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Buczek David M.
Di Pietro Paul J.
Scudiere John D.
Snitchler Gregory L.
American Superconductor Corporation
Fish & Richardson P.C.
Talbot Brian K.
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