JPH01107421A - AC superconducting conductor - Google Patents

Abstract

PURPOSE:To abate an AC loss by setting up a superconductive element wire in the central part and the outer circumferential part of a conductor, and installing a normal conductive metal layer in an intermediate part between the central part and the outer circumferential part and the outside of the outer circumferential part. CONSTITUTION:In an AC superconductor 1, a superconductive element wire 2 is divided into two pieces, and its one part is set up on the outer circumferential part and the rest in the central part respectively, then a normal conductive metal 10 is set up in the intermediate part. If so, a superconductive element wire group on the outer circumferential part basks in an outer magnetic field to an outer impressing magnetic field, but a magnetization loss is reduced as much as a portion for reducing the number of filament pieces, whereby a loss of the superconductive element wire group at the central part comes almost zero owing to a shielding effect by the outer circumferential part. Thus, the whole AC loss is surely abated. In addition, if the number of pieces of the superconductive element wire group to be set up on the outer circumferential part is reduced to the almost and the outer magnetic field is effectively shielded, the whole AC loss is further reducible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a superconducting conductor and a method for manufacturing the same, and particularly to a superconducting conductor suitable for superconducting AC equipment and a method for manufacturing the same.

[Conventional technology]

The superconducting conductors used in conventional AC equipment have been developed by placing the superconductor in the form of a filament in a normal conducting metal such as copper aluminum and arranging it in a concentrated manner around the outer periphery of the filament. FIG. 3 Below, the structure and effectiveness of the conventional example will be specifically described according to FIG.

As shown in the figure, the conventional AC superconducting conductor 1 has Nb −
A superconducting filament 4 such as T i , N b a S n etc. is provided with a superconducting strand 2 doubly coated with a first normal conducting metal 5 and a second normal conducting metal 6 on the outer periphery, and a third A normal conductive wire 3 in which a normal conductive metal 7 is coated with a fourth normal conductive metal 8 is placed in the center, and the outermost layer thereof is coated with a fifth normal conductive metal 9. The normal conducting metals 1 to 5 are copper, aluminum, and cupronickel.
species, or a combination of three species, especially the first
and the third normal conducting metal 5.7 is a low resistance metal, and the second
High resistance metals are often used as the normal conductive metals 6 and 8.9 with a temperature of 4.5 degrees. To reduce magnetization loss.

The superconducting wire 2 is thinned and has a diameter of about 1 μm,
The normal conductive wire 3 is also thinned to approximately the same dimensions in order to reduce eddy loss. The high-resistance metal is used to block the coupling current between the superconducting wires 2 and the eddy current between the normal conducting wires 3, and ultimately contributes greatly to reducing the AC loss of the AC superconducting conductor 1. . Further, the AC superconducting conductor 1 is twisted around the central axis so that the coupling current can be more effectively interrupted.

In order to increase the current capacity of the conductor, a plurality of AC superconducting conductors 1 shown here are bundled and twisted into a circular or rectangular shape. Furthermore, depending on the application, the outer periphery of the AC superconducting conductor 1 may be coated with an insulating layer.

When current flows through this AC superconducting conductor 1, it is biased toward the outer periphery of the conductor due to the skin action, and is concentrated in the superconducting filament 4, which has zero resistance. It does not flow into the normal conductor interposed between the superconducting strands, sufficiently suppressing Joule heat generation, and is expected to significantly reduce AC loss. Furthermore, if a current flows through the superconducting strands at the outer periphery, the self-magnetic field generated by this current becomes zero at the center, and there is no eddy loss in the normal conducting strands, resulting in an AC loss reduction effect. is further enhanced. The above are the effects of this type of conductor.

However, the above effectiveness is limited to cases where this type of conductor is a single wire. In order to reduce AC loss, superconducting filaments are made into ultra-fine wires, so the straight line of the manufacturing method rise line also becomes significantly thinner (<1wn), and its current capacity is also smaller (<number + A).
) It is extremely inconvenient in practice. Therefore, in order to increase the current as described above, it is common to bundle and twist a plurality of these single wires.

However, when twisted wires are used, magnetic fields from other adjacent single wires are applied perpendicularly to the single wire of interest (proximity effect), so the above effects cannot necessarily be expected. still,
Regarding superconducting wires for alternating current, for example, Japanese Patent Application Laid-Open No. 60-15
It is disclosed in Japanese Patent Application Laid-open No. 8510, Japanese Patent Application Laid-open No. 62-67156, and the like.

[Problem that the invention seeks to solve]

The above-mentioned conventional technology does not take into consideration practical use of large currents, and has a problem of increased loss due to the proximity effect associated with twisted wires.

The present invention has been made in view of the above-mentioned points, and its purpose is to provide a superconducting conductor as a single wire that can cope with large currents and has lower AC loss than before. and its production method.

[Means for solving problems]

The above purpose is for single-wire AC superconducting conductors.

A normal conductive metal layer is provided between the superconducting strands arranged on the inner and outer peripheries of the cross section and the superconducting strands arranged in the center. This is achieved by weakening the magnetomagnetic caking, by varying the number of superconducting wire groups arranged at the outer periphery and at the center, and by varying the twist pitch.

[Effect]

Breaking down the AC loss in an AC superconducting conductor by loss mechanism, the magnetization loss in the superconducting filament accounts for the majority at approximately 80%, the eddy loss in the normal conductor accounts for approximately 5%, and the remaining approximately 1%.
It is said that 5% is the coupling loss between the superconducting filaments via the normal conducting metal. Moreover, it is said that the loss due to the magnetic field is about two orders of magnitude (about 100 times) larger than the loss due to the current. Based on these two facts, if we consider the case where an alternating current flows through an alternating current superconducting conductor and a perpendicular alternating magnetic field acts on it (a stranded conductor for large current), we can assume that the superconducting filament is It is possible that alternating current loss can be reduced if the arrangement of the

In conventional AC superconducting conductors, superconducting filaments,
In other words, if the number of superconducting wires 2 is divided into two, some of them are placed on the outer periphery, the rest are placed in the center, and the normal conductive metal is placed in the middle. The group of superconducting wires in the center is exposed to an external magnetic field, but the loss (magnetization loss) is reduced by the reduction in the number of filaments, and the loss in the group of superconducting wires in the center becomes almost zero due to the shielding effect of the outer periphery. . Therefore, the overall AC loss is reliably reduced. If you want to reduce the number of superconducting wire groups placed on the outer periphery as much as possible to efficiently shield external magnetic fields,
Overall AC loss can be reduced. As a means of achieving this, there is a method of providing a sufficient distance between the outer periphery and the center, and placing a normal conducting (low resistance) metal in the middle, and a method of making the twist pitch of the superconducting wires on the outer periphery slightly longer. Sh.

There are two possible ways to strengthen the bond.

〔Example〕

An embodiment of the present invention is shown in FIG. 1, and its configuration.

The structure of the AC superconducting conductor 1 according to the present invention is as follows. Superconducting (Nb-T
i) A first normally conducting metal (copper) on the outside of the filament 4
5 and a second normal-conducting metal (cupro nickel) 6 are densely arranged, 857 in the center and 643 on the outer periphery, and a sixth normal-conducting wire is placed in the middle. metal(
Cupro-Nickel) 10 layers are provided, with a fifth layer on the outermost periphery.
A normally conducting metal (cupronickel, 40 μm thick) 9 was placed.

This specific manufacturing method will be described later. Further, for comparison, a conventional conductor having the same circles as the present example was separately prepared. In this embodiment, a set of seven superconducting filaments 4 having a diameter of 1 μm are embedded in the first normal conducting metal 5, but it is more common to form a three-layer structure for each filament. This configuration will not be considered a particular issue here.

Next, the operation of each component will be explained. Superconducting wires 2 are arranged at the outer periphery and the center, and serve to carry alternating current. The layer of normal electric core metal A10 in the middle part prevents electrical coupling between the superconducting strands in the center and the outer periphery, and also has the function of increasing the distance to some extent to weaken the magnetic coupling and reduce AC loss. Motsu. The outermost normal conductive metal 9 not only serves to firmly maintain the shape of the AC superconducting conductor 1, but also to prevent eddy currents and combined currents from flowing if it is a high resistance metal. In some cases, the second normal-conducting metal 6 constituting the superconducting wire 2, which has the function of reducing eddy currents and combined currents in the inner superconducting wire group and reducing overall AC loss, is also a normal-conducting metal. It has the same function as 9. Also, the superconducting strands in the center and the outer periphery were twisted with the same 4I111 pitch as the conventional conductor used in the comparative experiment.The twisting was done as described above. It has the effect of cutting off the electrical connection between the superconducting wires 2 and reducing AC loss.

Furthermore, the effects of the AC superconducting conductor 1 of the present invention will be described. FIG. 4 shows the results of AC loss measurements of the conventional AC superconducting conductor and the AC superconducting conductor according to the present invention.

The solid line shows the AC loss of the present invention, and the dotted line shows the AC loss of the conventional conductor. That is, when compared in an AC magnetic field of 1.0 T, the AC loss was reduced to 1/2.3 compared to the conventional conductor 1. This result suggests that the present invention is effective in reducing AC loss.

In this embodiment, it is possible to further reduce the AC loss by selecting different twist pitches for the superconducting wire group in the center and the superconducting wire group in the outer periphery. As already mentioned, in order to efficiently shield the externally applied magnetic field and reduce the magnetic field of the superconducting strands in the center and the normal conducting metal layer 10 in the middle, it is necessary to adjust the twist pitch of the superconducting strands in the outer periphery. It is only necessary to make it longer so that the coupling current can flow more easily. An increase in the coupling current leads to an increase in the coupling loss, but it does not make the twist pitch infinite, and the coupling loss is only 1% of the total loss.
Considering that it is 75 or less, it will not affect many people. In addition, if the superconducting strands in the center and the outer periphery are twisted at the same pitch, the specific vane inductance of the outer periphery will be larger than that in the center, making it difficult for alternating current to flow, and alternating current will no longer flow evenly through the superconducting strands. there is a possibility.

Therefore, it is necessary to increase the twist pitch at the outer periphery to lower the impedance and make it equal to that at the center. This twist pitch must be selected in a direction that reduces AC loss, taking into account the difference in the number of superconducting strands 2 included in the center and the outer periphery. The twist pitch of the parts is not necessarily long, and the twist directions are not necessarily the same.

Another embodiment of the present invention will be described with reference to FIG.

The difference in structure from FIG. 1 is the normal conductive metal layer 10 in the middle.
It is. That is, in FIG. 1, a single normal-conducting metal vibrator is used, but in FIG. 2, this is multilayered, and different types of normal-conducting metals and normal-conducting strands 3 are combined. The details are shown in Figure 2 (
c) shows four configurations. The cross-section a shows that the sixth normal conductive metal 11 is placed on the inside and the outside, and the seventh normal conductive metal 12 is placed in the middle, and the cross-section b shows the opposite arrangement. Further, in the C section, the eighth normal conductive metal 13 is arranged inside, and the normal conducting cables 3 are arranged densely on the outside, and in the D section, the arrangement is reversed.

This is a countermeasure when it is necessary to increase the amount of low-resistance metal to improve the stability of the AC superconducting conductor 1. If the low-resistance metal is placed in a pipe shape, eddy loss and coupling loss will increase. It is designed to be subdivided or multi-layered. Naturally, various methods of subdivision and multilayering can be considered in addition to those described above.

The expected effects of this example are reduction of loss and further improvement of stability, as in the previous example.

A very basic example of a manufacturing method for embodying the present invention will be described below.

FIG. 5 shows the first manufacturing method of the present invention.

(a) shows the starting point of manufacturing, and the superconducting wire 14 in the center has a round wire shape and has already been twisted. The superconducting wires 15 and 15' forming the outer circumference are rectangular wires, and the required number is determined by their dimensions, twist pitch, etc. As shown in (b), these superconducting wires have a superconducting wire 14 at the center and a superconducting wire 15°1 at the outer periphery.
Wrap 5'. Then, for example, they were passed through a die and brought into close contact with each other to form a single AC superconducting conductor 1 as shown in (c).

FIG. 6 shows a second manufacturing method of the present invention.

(a) shows the starting point of manufacturing, where the superconducting wire 14 that forms the central part is round and has already been twisted, and the superconducting wire 16 that forms the outer periphery is pipe-shaped and is similar to this. Added a twist. These superconducting wires (b
), the superconducting wire 14 serving as the central portion is inserted into the superconducting wire 16 serving as the outer peripheral portion. Then, they were passed through a die and brought into close contact with each other to form a single AC superconducting conductor 1 as shown in (C). In the above two manufacturing methods, no particular twist was added after the close contact processing, but it is of course possible to further twist after the close contact processing to obtain a desired twist pitch. Further, the twist directions in the central part and the outer peripheral part do not need to be the same, and may be in opposite directions.

Needless to say, it is extremely easy to provide the electrically conductive core Wjt layers 9 and 10 between the center and the outer periphery and at the outermost periphery in the above-mentioned fixing method.

The embodiment explained in FIG. 1 follows the manufacturing method explained in FIG. The superconducting wire 14 in the center is coated with a normal conductive metal layer 9 which is the outermost layer, and the superconducting wire 14 in the center is manufactured in accordance with the usual manufacturing method for ultra-fine multi-filament wires.

The number of superconducting filaments (the number of superconducting strands 2) and the twist pitch are as described above.

〔Effect of the invention〕

According to the present invention as described above, it is possible to reduce the AC loss even at the maximum level, and therefore, the industrial effect in the field of AC application of superconductivity is enormous.

[Brief explanation of the drawing]

FIG. 1(a) is a cross-sectional view showing an AC super@freezing conductor according to an embodiment of the present invention, FIG. 1(b) is a detailed cross-sectional view of the superconducting wire, and FIG. A sectional view of an AC superconducting conductor showing another example, FIG. 2(b) is a detailed sectional view of the superconducting wire, and FIG. 2(c) is a sectional view of the conductor showing various combinations of normal conducting metal layers. , FIG. 2(d) is a detailed sectional view of the normal conductive wire. FIG. 3(a) is a sectional view showing a conventional AC superconducting conductor, and FIG. 3(b) is a detailed sectional view of the superconducting strand. Figure 3(c) is a cross-sectional view of the normal conductive wire, and Figure 4 is the same.
FIG. 3 is a characteristic diagram showing the actually measured AC loss characteristics of the conventional AC superconducting conductor and the AC superconducting conductor of the present invention. Figure 5 (a), (b), (c) and Figure 6 (a),
(b). (Q) is a process order diagram showing examples of manufacturing methods for embodying the AC superconducting conductor of the present invention. 1... superconducting conductor for alternating current, 2... superconducting strand, 3...
・・Normal conductive wire, 4・Superconducting filament, 5・・
・First normal conductive metal, 6... Second normal conductive metal, 7.
...Third normal conductive metal, 8...Fourth normal conductive metal, 9
...Fifth normal conducting metal, 10... Normal conducting metal layer, 1
1... Sixth normal conducting metal, 12... Seventh normal conducting metal, 13... Eighth normal conducting metal, 14... Superconducting wire serving as central portion, 15.15'...・Superconducting wire serving as the outer periphery, 16... Pipe-shaped superconducting wire serving as the outer periphery.゛Representative Patent Attorney Small Jl + Katsuo;, 9)゛--7 Chestnut 3 Figure (b) (C) Kyou 4-ku f-';・21I214r, (1 (Seventh Procedural Amendment (Method) % Formula % Title of Invention Superconducting Conductor and Manufacturing Method hli Each 'ICf'l',!-Force Relationship 'L?J'l': I
! Igr1 Person (51) (Hitachi, Ltd.)
Contents 1 of the X-f quadrant section correction of No. 1 amendment, Marunouchi-5-chome, 111-ku, Chiyo, Tokyo, 1+x+1, and Fig. 3 of the drawing of the present application will be amended as shown in the attached drawing.

Claims (1)

[Scope of Claims] 1. In an ultrafine multi-core superconducting conductor consisting of a large number of superconducting strands in which the superconductor is double coated with a low-resistance layer and a high-resistance layer of a normal conducting metal, the superconducting strands are A superconducting conductor characterized in that a normal conductive metal layer is disposed at the center and outer periphery of the conductor, and a normal conductive metal layer is provided between the center and the outer periphery and outside the outer periphery. 2. A superconducting conductor according to claim 1, characterized in that the superconducting wire groups in the central part and the outer peripheral part are twisted at different pitches. 3. The product described in claim 1, characterized in that the normal conductive metal layer disposed between the central part and the outer peripheral part is a composite of a low-resistance metal layer and a high-resistance metal layer. superconducting conductor. 4. In a method for manufacturing an ultrafine multi-core superconductor consisting of a large number of superconducting strands in which the superconductor is double coated with a low resistance layer and a high resistance layer of normal conducting metal, the superconducting strands are coated with a conductor. A superconducting conductor characterized in that, when arranged in a central part and an outer peripheral part, one or more superconducting wires are wound around the central superconducting wire to form the outer peripheral part, and then the superconducting wires are brought into close contact with each other. production method. 5. In a method for manufacturing an ultrafine multi-core superconductor consisting of a large number of superconducting strands in which the superconductor is double coated with a low resistance layer and a high resistance layer of a normal conducting metal, the superconducting strands are coated with a conductor. When placing the superconducting wire in the center and the outer periphery, the superconducting wire that will be the center part is twisted in advance, and the pipe-shaped superconducting wire that will be the outer periphery is twisted with a pitch different from this twist pitch and is manufactured separately. 1. A method for manufacturing a superconducting conductor, which comprises inserting a superconducting wire to serve as a central portion into a pipe-shaped superconducting wire, and then bringing the superconducting wire into close contact with each other.