JPH04329219A - Oxide superconductor - Google Patents

Abstract

PURPOSE:To provide an oxide superconductor of which the electric superconductive characteristics are less deteriorated even when a large electric current is passed therethrough. CONSTITUTION:Conductors 1 and 4 are longitudinally disposed in a manner that they are circumferentially arranged in parallel. In each of the conductor arrangements 1 and 4, adjacent two of the conductors are alternately located so that one may be a forward current path and the other a backward current path.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to oxide superconducting conductors, and more particularly to the structure of oxide superconducting conductors that can be used as conductors for bus bars through which large currents flow.

0002

2. Description of the Related Art In recent years, yttrium-based, bismuth-based, and thallium-based oxide superconductors have attracted attention as superconducting materials exhibiting higher critical temperatures.

Since these become superconducting at liquid nitrogen temperature (77.3 K), they are expected to be used as current leads for cable conductors, coils, and superconducting magnets.

[0004] The large current busbar conductors currently in use or scheduled to be used in the future have a current of 3.
There are those of 0KA to 45KA.

[0005]

[Problems to be Solved by the Invention] Figure 1 shows the Jc (critical current density) - B (
FIG. 2 is a diagram showing magnetic flux density characteristics. When a large current as described above is applied to a single conductor, the self-magnetic field increases from 3000 to 5
It becomes 000 Gauss. As is clear from Figure 1, under such a high magnetic field, the critical current density (Jc) is reduced to 1/
It drops to 3 to 1/5.

An object of the present invention is to provide an oxide superconducting conductor whose superconducting properties are less degraded even when a large current flows.

[0007]

[Means for Solving the Problems] In the oxide superconducting conductor of the present invention, the conductors are arranged in a ring shape in the circumferential direction along the longitudinal direction, and the conductors are connected to the forward and backward paths of current between adjacent conductors. It is characterized by being arranged alternately so that

FIG. 2 is a sectional view showing an embodiment of the present invention. Referring to FIG. 2, ten fins 3 are formed at equal intervals on the outer circumferential surface of the pipe-shaped external support 2 and protrude outward, and ten external conductors are arranged between the fins 3. Bundle 1 is placed. The external conductor bundle 1 is a conductor formed into a bundle by arranging tape-shaped wires in three horizontal rows and stacking a plurality of these.

A pipe-shaped internal support 5 is also provided within the external support 2 . On the outer peripheral surface of the internal support body 5, ten fins 6 are provided at equal intervals and protrude outward. Between these fins 6, an inner conductor bundle 4
A total of ten inner conductor bundles 4 are arranged around the inner support 5. The internal conductor bundle 4 is formed into a bundle by arranging two tape-shaped wires horizontally and stacking a plurality of layers.

As shown in FIG. 2, the outer conductor bundle 1 and the inner conductor bundle 4 are arranged alternately so that the current flows between adjacent conductors in an outgoing and incoming path.

[0011]

[Operation] Figure 3 shows the current I and magnetic field H in a wire with radius a.
FIG. When the distance r from the center of the conductor is larger than the radius a of the conductor, a magnetic field expressed by the following equation 1 is generated.

0012

[Math 1]

Further, when the distance r from the center of the conductor is smaller than the radius a of the conductor, a magnetic field H expressed by the following equation 2 is generated.

[0014]

[Math 2]

FIG. 4 shows the relationship between the distance r from the center of the wire and the magnetic field H from the above equations 1 and 2.

As is clear from FIG. 4, the magnetic field generated is largest at the surface of the conductor, ie, at the portion where r=a.

For example, 45K is applied to a conductor with a diameter of 40mm.
When a current of A is applied, the magnetic field on the surface of the conductor is as follows:
It is expressed as

[0018]

[Math 3]

Further, the magnetic flux density is expressed by the following equation 4.

[0020]

[Math 4]

In order to reduce the generated magnetic field, it is necessary to reduce the current I, and therefore it is preferable to divide the conductor into a plurality of parts as in the present invention.

[0022] In the present invention, a plurality of divided conductors are further arranged alternately so that the current flows between adjacent conductors in an outgoing and incoming path, thereby canceling out the effects of magnetic fields from other conductors. I have to.

[0023]

EXAMPLE An oxide superconducting conductor according to the present invention as shown in FIG. 2 was prepared. As the outer conductor bundle 1, 6500
10 conductors of A, the inner conductor bundle 4 is 2500A
As shown in FIG. 2, ten conductors are arranged alternately so that adjacent conductors form forward (+) and backward (-) current paths. When a current of 45 KA was passed through this conductor, the maximum magnetic flux density Bm of the conductor was 1600 Gauss.

For comparison, a conductor as shown in FIG. 5 was prepared. In the comparative conductor shown in FIG. 5, the outward path (+) of the conductor was collected on one side of the outer conductor bundle 1 and the internal conductor bundle 4, and the return path (-) of the conductor was collected on the other side, making it an oxide superconducting conductor. When a current of 45 KA was passed through this conductor, the maximum magnetic flux density Bm of the conductor was 3870 Gauss.

When the magnetic flux density distributions of the oxide superconducting conductors of the example shown in FIG. 2 and the comparative example shown in FIG. 5 were analyzed, it was found that in the example shown in FIG. On the other hand, in the superconducting conductor of the comparative example shown in FIG. 5, 80% of the portions had a magnetic flux density of 1000 Gauss or more.

Table 1 shows the magnetic flux density and its area ratio in the embodiment shown in FIG.

[0027]

[Table 1]

Table 2 shows the magnetic flux density and its area ratio in the comparative example shown in FIG.

[0029]

[Table 2]

[0030] Bi-based superconducting wire has a magnetic flux density of 1000
In the Gaussian section, the critical current density (Jc) drops to 1/2 of that in the zero field case. Further, at 3500 Gauss, the critical current density is reduced to 1/3.

Accordingly, when calculated from Table 1, the magnetic flux density of the oxide superconducting conductor of the example according to the present invention is 83% of the characteristic at zero magnetic field.

On the other hand, the oxide superconductor of the comparative example has
Calculating from Table 2, it is 43% of the zero magnetic field.

[0033] Therefore, by following this invention,
Performance can be almost doubled and twice as high critical current density can be obtained. Therefore, the conductor itself can be made more compact.

[0034]

As explained above, according to the present invention, even when a large current is passed, a decrease in the critical current density can be significantly suppressed. Therefore, the conductor can be made more compact.

Therefore, the oxide superconducting conductor according to the present invention can be effectively used as a cable conductor, a busbar conductor, a current lead to a coil, a superconducting magnet, and the like.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the critical current density (Jc)-magnetic flux density (B) characteristics of a bismuth-based superconducting wire at 77.3K.

FIG. 2 is a sectional view showing an embodiment of the invention.

FIG. 3 is a diagram showing the relationship between current I and magnetic field H in a wire with radius a.

FIG. 4 is a diagram showing the relationship between the distance r from the center of the wire and the magnetic field H.

FIG. 5 is a sectional view showing a superconducting conductor of a comparative example.

[Explanation of symbols]

1 Outer conductor bundle 2 External support 3 Fin 4 Internal conductor bundle 5 Internal support 6 Fin

Claims (1)

[Claims] 1. An oxide superconducting conductor comprising conductors arranged in a ring shape in the circumferential direction along the longitudinal direction, wherein the conductors are arranged alternately so that the conductors serve as an outgoing path and a returning path for current between adjacent conductors. An oxide superconducting conductor, characterized in that: