Superconductor technology: apparatus – material – process – High temperature devices – systems – apparatus – com- ponents,... – Dynamoelectric machine – or components thereof
Reexamination Certificate
2001-09-25
2004-03-23
Dunn, Tom (Department: 1725)
Superconductor technology: apparatus, material, process
High temperature devices, systems, apparatus, com- ponents,...
Dynamoelectric machine , or components thereof
C505S237000, C310S261100, C428S702000
Reexamination Certificate
active
06711421
ABSTRACT:
BACKGROUND OF INVENTION
The present invention relates generally to superconducting tape, and more particularly to a metal reinforced superconducting tape.
Synchronous electrical machines having field coil windings include, but are not limited to, rotary generators and rotary motors. These machines generally comprise a stator and rotor that are electromagnetically coupled. The rotor may include a multi-pole rotor core and one or more coil windings mounted on the rotor core. The rotor cores may include a magnetically-permeable solid material, such as an iron-core rotor.
Recently, superconducting coil windings have been developed for rotors. Superconducting coils are advantageous because they have effectively no resistance. High temperature superconducting coil windings are formed of brittle ceramic superconducting tape. The tape may be formed of a high temperature superconducting material, such as a Bi
1.8
Pb
0.4
Sr
2
Ca
2
Cu
3
O
10+x
(BSCCO 2223), Bi
2
Sr
2
Ca
1
Cu
2
O
8+x
(BSCCO 2212), and YBa
2
Cu
3
O
7−x
(YBCO 123). This tape must be cooled to a temperature at or below a critical temperature to achieve and maintain superconductivity.
When this superconducting tape is put under tension, the ceramic grains in the tape degrade, resulting in a decrease in the critical current carrying capability of the superconducting tape. To address this issue, a paper by K. G. Herd et al. titled “Development and Fabrication of a Bi-2223 Racetrack Coil for Generator Applications”, in IEEE Transactions on Applied Superconductivity, Vol. 7, No. 2 (June 1997) page 531, incorporated herein by reference, describes an epoxy impregnated silver sheathed BSCCO 2223 superconducting tape laminated to copper foils for strength enhancement.
Furthermore, U.S. Pat. No. 5,987,342, incorporated herein by reference, discloses laminating the superconducting tape to a pre-tensioned metal (i.e., steel, copper or superalloy) tape having a thermal expansion coefficient greater than that of the superconducting tape. The metal tape may be laminated to the superconducting tape using solder, epoxy or solderless ultrasonic welding. As the tapes cool after a high temperature lamination, the metal tape causes the superconducting tape to be placed under compression due to the difference in the coefficients in thermal expansion and due to the pre-tensioning of the metal tape. The metal tape improves the superconducting tape's tolerance to tensile and bending stresses, by placing the superconducting tape under compression.
SUMMARY OF INVENTION
In accordance with one preferred aspect of the present invention, there is provided a reinforced superconducting tape comprising a superconducting tape comprising a superconducting ceramic material, a first metal reinforcing layer having a greater coefficient of thermal expansion than that of the superconducting tape, and a second metal reinforcing layer having a greater modulus of elasticity than the superconducting tape and the first reinforcing layer.
In accordance with another preferred aspect of the present invention there is provided an electric machine, comprising a stator comprising stator coils, a rotor comprising a rotor core, and a coil winding around the rotor core. The coil winding comprises a superconducting tape comprising one or more ceramic superconductor filaments located in a noble metal sheath, a first metal reinforcing layer having a greater coefficient of thermal expansion than that of the superconducting tape, and a second metal reinforcing layer having a greater modulus of elasticity than the superconducting tape and the first reinforcing layer.
In accordance with another preferred aspect of the present invention, there is provided a method of making a reinforced superconducting tape, comprising providing a superconducting tape comprising a superconducting ceramic material, forming a first metal reinforcing layer having a greater coefficient of thermal expansion than that of the superconducting tape, and forming a second metal reinforcing layer having a greater modulus of elasticity than the superconducting tape and the first reinforcing layer.
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Christopher G. King et al.: “Mechanical Stabilization of BSCCO-2223 Superconducting Tapes,” IEEE Transactions on Applied Superconductivity, Jun. 1997, pp. 2046-2050, vol. 7, No. 2, IEEE, Jun. 1997.
Kenneth G. Herd et al.: “Development and Fabrication of a Bi-2223 Racetrack Coil for Generator Applications,” IEEE Transactions on Applied Superconductivity, Jun. 1997, pp. 531-534, vol. 7, No. 2, IEEE, Jun. 1997.
Howard E. Boyer et al.: “Metals Handbook, Desk Edition,” pp. 1•44-1•48, 1•51, 2•6, 29•14-29•42, American Society for Metals, Metals Park, Ohio, no date available.
Laskaris Evangelos Trifon
Wang Yu
Cooke Colleen P.
Dunn Tom
Foley & Lardner
General Electric Company
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