JPH05109323A - Superconductive assembled conductor - Google Patents

Abstract

PURPOSE:To provide improvement in the current density required for an assembled conductor by using wire rods each reading a low-resistance value under a current density of not less than the critical current density of oxide group superconductive wire-rods for at least one part of the oxide group superconductive wire-rods forming the assernbled conductor. CONSTITUTION:For an oxide group superconductive wire-rods are used different types of tape-like wire-rods 1a and 1b each comprising a core 2 which is made of an oxide group superconductor, such as Y-Ba-Cu-O, Bi-Sr-Cu-O, Tl-13a-Cu-C, La-Na-Cu-O or the like, coated with a film 3 made of Ag, Cu, Al or the like. A plurality of the wire rods 1a, 1b are laminated upon one another, and subsequently fine lead-wire 4 is wound round the resultant laminate to assemble the wire rods into a conductor. Each of the wire rods 1a, 1b is manufactured through the process of reducing the resistance value of the wire rod given under a current density of not less than the critical current density of the wire rod by priority to the resistance value of the wire rod given under the critical current density. This process provides improvement in the current density required for the resultant assembled conductor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aggregate conductor using an oxide-based superconducting wire.

[0002]

2. Description of the Related Art In order to increase the current capacity of a superconducting conductor, it has been studied to assemble oxide-based superconducting wires into a conductor.

The current density (Jc) that can flow in the superconducting wire changes depending on the magnetic field (B). The Jc-B characteristics differ depending on the material or temperature of the superconducting wire, and even the materials of the same system may differ greatly depending on the heat treatment conditions and the difference in additives. Also, although oxide-based superconducting wires are currently under development, not only the Jc-B characteristics but also the resistance value under a current density of Jc or more due to differences in additives, compounding ratio, heat treatment conditions, surface-reduction processing conditions, etc. Is also different.

[0004]

It is known that the critical current (Ic) of an oxide-based superconducting wire decreases even in a weak magnetic field of several mT. Therefore, even when the oxide-based superconducting wires are assembled to increase the current capacity, the Ic as the assembled conductor is restricted by the self-magnetic field value due to conduction of the conductor.

When designing such a superconducting collective conductor, the same magnetic field-critical current density (Jc-B characteristic) of each wire is often used. However, the self-magnetic field distribution in the conductor cross section is not uniform, and bundling wires having the same Jc-B characteristics is not the best method for increasing Ic as a collective conductor.

Conventionally, as a method of designing a superconducting conductor, J
The required current value is determined on the assumption that it will be used at a current of c or less. The Jc value of oxide-based superconducting wire has not reached a practical level, and high Jc has become a major technical issue.

An object of the present invention is to provide a superconducting collective conductor capable of improving the required current density of a large-current-capacity conductor using an oxide-based superconducting wire.

[0008]

Means for Solving the Problems The gist of the present invention is to provide a superconducting element wire for use as an assembly conductor of an oxide-based superconducting wire,
It is to improve the required current density of the superconducting conductor by using a current of Jc or more as a required current for at least a part of the wires.

In this case, as the oxide-based superconducting wire,
For example, Y-Ba-Cu-O, Bi-Sr-Cu-O, B
i-Sr-Ca-Cu-O, Tl-Ba-Cu-O, T
l-Ba-Ca-Cu-O, Tl-Sr-Ca-Cu-
O, La-Na-Cu-O, La-Ba-Cu-O, L
Ag, C in oxide-based superconductors such as a-Sr-Cu-O
A material coated with a normal conductor such as u, Al, or an alloy mainly containing them is used.

At least a part of the wire made of such a wire is manufactured by giving priority to the reduction of the resistance value under the current density of Jc or more rather than the improvement of the Jc value.

[0011]

EXAMPLE FIG. 1 shows the structure of a superconducting collective conductor prototyped according to the present invention. Here, a core 2 made of a Tl-based oxide superconductor is used as the oxide-based superconducting wire 1.
The tape-shaped wire rods 1a and 1b of different types having the coating 3 made of Ag on are used, a plurality of the tape-shaped wire rods 1a and 1b are stacked, and then the thin conductive wire 4 is wound to be assembled. The dimensions of the tape-shaped wire rods 1a and 1b are all the same, with a thickness of 0.15 mm, a width of 2.7 mm, and a superconducting space factor of about 30%. After 10 sheets and 30 pieces of the wire rods 1b are arranged on the inner side and laminated, the conductor wire 4 having a small diameter is wound around the outer periphery thereof to be assembled.

In this case, the manufacturing conditions of the respective wire rods 1a and 1b were the same until the heat treatment at 900 ° C. for 50 hours was repeated four times, after which the heat treatment at 800 ° C. for 20 hours was added to the wire rod 1a. Thus, a wire having a difference in resistance value under the current density of the Jc value of the wire or more is obtained, and the assembly conductor is required to be energized with the current of the Jc value or more of the wire with the lower Jc value. It is regarded as a driving load.

FIG. 4 shows the liquid nitrogen temperature (7
The relationship between the voltage (V) and the current (I) (V-
I characteristic), the resistance is generated at a current value of 200 A or more, but the resistance when the current is 1000 A is much smaller than the resistance value of the copper wire aggregate conductor.

Although the oxide superconducting wire has a low Jc value, it has a feature that the resistance value is small in the current-carrying state of Jc or more. Therefore, it is possible to improve the required current density as a superconducting wire aggregate conductor by utilizing this characteristic.

When the collective conductor of the superconducting wire is energized, the self-magnetic field distribution on the cross section of the conductor is not uniform, and some wires exceed Jc of the conductor and other wires become Jc or less. The critical current as the collective conductor in such a case is determined by the characteristics of the wire having the lowest Jc value.
If it is used in a low resistance state on the assumption that it is energized over c, each wire can fully utilize its performance, and it can be applied to superconducting power cables, conductors of current leads, etc. Another example of the conductor is shown, in which a plurality of oxide-based superconducting wires are alternately arranged around the hollow pipe 6 made of a stabilizing material such as Cu or Al, and wire rods 5a and 5b of different types are alternately arranged. The wire rods 5a and 5b treated in the same manner as the wire rods 1a and 1b in FIG. 1 are used.

In the case of this example, the cooling effect can be enhanced by flowing a cryogen such as liquid nitrogen or liquid helium in the hollow pipe 6.

FIG. 3 shows another example of the collective conductor. For example, a plurality of tape-shaped oxide-based super electric wire materials are provided inside a stabilizing material 8 in which a copper plate is formed in a U shape. Wire rod 1b, and type A wire seat 1a on the outer side, which are housed in a laminated state and collectively integrated with low temperature solder 7 etc., are joined together through a tape-shaped electric insulating layer 9 to form a current reciprocating type. Is.

In any of the conductor configurations, the required operating load is set under the current flow of the superconducting critical current density or less.

[0019]

As is apparent from the above description, according to the present invention, wire rods to be assembled are provided on the assumption that a current density higher than the critical current density as the assembly conductor is the required current density during operation. Since a wire having a low resistance value under a current density equal to or higher than the critical current density is used for at least a part of the above, the performance of each wire can be fully utilized, and the required current density as an aggregate conductor can be improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram outlining an embodiment of a superconducting conductor according to the present invention.

FIG. 2 is an explanatory view showing another example of a superconducting conductor.

FIG. 3 is an explanatory view showing another example of a superconducting conductor.

FIG. 4 is a Jc-B characteristic diagram.

[Explanation of symbols]

 1a, 1b, 5a and 5b Oxide-based superconducting wire 2 Oxide-based superconducting core 3 Ag coating 4 Conductive wire 6 Hollow pipe 7 Low temperature solder 8 Stabilizer 9 Electrical insulation layer

Claims (1)

[Claims] 1. A conductor obtained by assembling a plurality of oxide-based superconducting wires containing a coating material of a normal-conducting metal, wherein at least a part of the wires has a low resistance value under a current density of a critical current density or higher. A superconducting collective conductor characterized by using.