JPH0320911A - High temperature superconductor and its conjunction structure - Google Patents

Abstract

PURPOSE:To achieve high Jc and large current capacity by making a unified final superconductor by bundling a plurality of component superconductors having a small cross section surface area, a large ratio of the circumference/ surface area of the cross section, and thus high critical current density (Jc). CONSTITUTION:A plurality of ceramic-based component superconductors 1 having relatively small cross section surface area and a large ratio of the circumference/surface area of the cross section are bundled to give a final superconductor 2. With this structure, oxygen is enoughly diffused in the superconductors 1 and thus Jc of the final superconductor 2 is kept as high as that of each component superconductor 1. Each superconductor 1 is inserted into a good conductor sheath of such as copper and then inserted into a good conductor block 4 and a plurality of the resultant superconductors 1 are connected electrically in series. Or, each of the superconductors 1 is bound with a current balancing resistor 5 having a good conductor sheath 3 between them and then inserted into a good conductor block 4 of such as copper and bound electrically. By this method, critical current decrease owing to current flow imbalance in a specific superconductor 1 is suppressed to low level.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to increasing the current density and large current capacity of a high temperature superconductor.

(Prior Art) Generally, it is said that the critical current density (hereinafter abbreviated as J0) of a ceramic-based high-temperature superconductor containing yttrium or bismuth tends to increase as the cross-sectional area becomes smaller. One of the major reasons for this is thought to be that oxygen is not sufficiently diffused into the conductor during sintering, and a superconducting layer is formed only on the surface of the conductor. That is, the diffusion distance of oxygen from the conductor surface is almost determined only by factors such as the density of the material or the density of the material, and has little to do with the size and shape of the cross section of the conductor.

Therefore, for example, it is clear that as the conductor cross-sectional area becomes smaller, the overall superconducting layer cross-sectional area increases, and J0 improves accordingly. In other words, if we consider increasing the cross-sectional area of the conductor in order to increase the current capacity, not only will J0 decrease, but we will also have the difficulty of not being able to increase the current capacity in proportion to the increase in the cross-sectional area. there were. (Problems to be Solved by the Invention) An object of the present invention is to provide a structure of a high-temperature superconductor that can achieve a high J0 and a large current capacity.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention uses a large number of elementary superconductors that have a relatively small cross-sectional area and a large value of the circumference/cross-sectional area of the cross section, and therefore have a high J0. The final superconductor is made up of a single piece of paper.

Further, at the end thereof, current balancer resistors having the same resistance value are connected to each element superconductor, and then the current balancer resistors are joined together. Alternatively, after each elemental superconductor is embedded and bonded in a good conductor sheath, each good conductor is bonded as one body.

(Function) In such a configuration, oxygen diffuses sufficiently within the elemental superconductors, so that the final superconductor has a high Jc, similar to that of the elemental superconductors. keep it. Furthermore, in order to increase the capacity, it is sufficient to simply connect a large number of such elementary superconductors in parallel, so the manufacturing method is easy.

On the other hand, the end connection structure between elemental superconductors is connected via a balancer resistor to maintain current balance, or has a structure with little variation in contact resistance, so critical Current (hereinafter referred to as ■).

(abbreviated as ) is small.

(Example) The present invention will be described below with reference to an example shown in the drawings.

Figure (3) shows a ceramic element superconducting body with a relatively small cross-sectional area and a relatively large value of circumference/cross-sectional area. A final superconductor 2 as shown in FIG. 2 is constructed by bundling together a large number of these elementary superconductors 1.

In this case, since the element superconductor 1 has a large value of the circumference/cross-sectional area of its cross section, its proportion in the oxygen diffusion region of the sintered body, that is, the total cross-sectional area of the superconducting layer, is also relatively large. Therefore, J is high. It can be expected to have a value. On the other hand, since the final superconductor 2 is made up of many elemental superconductors l,
J0 will maintain the same high value as element superconductor 2.
On the other hand, it is clear that the current capacity increases in proportion to the number of elastic element superconductors 1.

FIGS. 3 and 4 show the joining structure of the terminal portion of the final superconductor. In FIG. 3, the elemental superconductors 1 are each inserted into a good conductor sheath 3 such as copper, and then inserted into a good conductor block to electrically connect a plurality of elemental superconductors 1 in parallel. Here, each joint surface is joined by a method such as brazing. Now, since the element superconductor 1 is inserted into the good conductor sheath 3 and bonded, the bonding area is large, and even if some external force is applied to the bonded part, there is little peeling of the bonded surface, so it has high reliability and low contact resistance. Extremely small joints can be achieved.

On the other hand, in FIG. 4, after each elemental superconductor 1 is connected to a current balance resistor 5 through a good conductor sheath 3, a plurality of elemental superconductors 1 are electrically connected by inserting and joining into a good conductor block such as copper. It is connected to. Here, the resistance values of the current balancing resistors 5 are selected to be equal and sufficiently larger than the contact resistance of the entire joint surface. This makes the current distribution in each element superconductor 1 substantially uniform. In other words, the current distribution becomes non-uniform due to the unbalance of the contact resistance at the junction, causing a biased current toward a specific element superconductor 1. can be suppressed from decreasing.

〔Effect of the invention〕

In the present invention, a final superconductor is constructed by combining a large number of allotropic superconductors that have a relatively small cross-sectional area and a high value of J0 due to the large values of circumference/cross-sectional area, so that a high-temperature superconductor with a high J0 and a large current capacity can be obtained. can be provided.

[Brief explanation of drawings]

1 and 2 are perspective views showing embodiments of the configuration of a high temperature superconductor diagram according to the present invention, and FIGS. 3 and 4 are sectional views showing embodiments of the joint portion of a high temperature superconductor according to the present invention, respectively. It is. 1... Elemental superconductor 2... Final superconductor 3.
...Good conductor sheath 4...Good conductor block 5...
・Resistor for current balance

Claims (1)

[Claims] (1) Since the cross-sectional area is relatively small and the value of the circumference/cross-sectional area is large, a large number of ceramic-based elementary superconductors are used in which the oxygen diffusion region occupies a relatively large proportion of the whole during sintering. A high-temperature superconductor characterized in that the final superconductor is formed by binding. (2) The element superconductors are electrically connected in parallel by inserting and bonding each of the ceramic element superconductors into a good conductor sheath and then inserting and bonding these good conductor sheaths into a good conductor block. Joint structure of high-temperature superconductor. (3) By inserting and joining a current balancing resistor to the other end of a good conductor sheath with a ceramic element superconductor joined to one end, and then inserting and joining these current balancing resistors into a good conductor block. , a high-temperature superconductor junction structure characterized by electrically connecting each elemental superconductor in parallel.