JPS62285319A - Ac superconductor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Industrial Application] This invention relates to an AC superconducting conductor having ultra-fine multifilament filaments.

[Prior Art] AC loss in a superconducting conductor is roughly divided into hysteresis loss, which depends on the filament diameter, and coupling loss, which depends on the twist pitch and resistance of the matrix metal. In recent years, the development of AC superconducting conductors for use at 50 to 60 Hz has been actively progressed. For example, in NbTi superconducting conductors, conductors with filament diameters of 1 micron or less are being developed.

However, in order to reduce the filament diameter and twist pitch, such wire rods have an outer diameter of lll1f.
less than flφ, for example 0. 3mmφ to 0, lff1
The thickness is about mφ, and for practical use, a process of composing a large number of wires is required. Furthermore, in order to reduce loss due to coupling current between the strands, it is preferable that the cable wires be insulated.

FIG. 5 shows a cross-sectional view of an example of a conventional large-capacity conductor with reduced AC loss. In Figure 5, 0.2a
The strand 1 of ++aφ is covered with an insulator 2 made of formal having a thickness of 25 μm.

Seven strands of wire 1 are twisted, and seven of the strands are further twisted, and the strands are covered with an insulating tape 4 made of, for example, heat-resistant aromatic polyimide.

[Problems to be solved by the invention]However, in a conductor having the structure shown in Fig. 5,
The proportion occupied by the space 3 and the insulator 2 has become very large. For example, in the conductor 7 shown in FIG. The cross-sectional area ratio is 36.2%. As the proportion of space and insulators increases, the rigidity of the conductor itself decreases, so when applied to superconducting magnets, the conductor may become magnetically unstable due to heat generated by friction, or may become distorted due to expansion. This caused problems such as deterioration of the conductor. Furthermore, since the current density in the conductor becomes low, a problem arises in that a high magnetic field cannot be generated.

Therefore, an object of the present invention is to provide an AC superconducting conductor having high conductor rigidity and high current density.

[Means for Solving the Problems] The AC superconducting conductor of the present invention is constructed by twisting together a plurality of superconducting strands each having an ultra-fine multifilament filament and covered with an insulator. By molding and compressing the combined superconducting strands, the superconducting strands are arranged close to each other.

[Function] In the AC superconducting conductor of the present invention, since the superconducting strands are arranged close to each other, the proportion of the space interposed between the superconducting strands is reduced. Therefore, the proportion of the highly rigid metal portion becomes relatively large, and the rigidity of the conductor itself is increased. Furthermore, since the superconducting strands are arranged close to each other, it becomes a conductor with high current density.

[Example] FIG. 1 is a sectional view showing a conductor that is an example of the present invention. In FIG. 1, the strand 1 of 0.2+mnφ is
It is covered with an insulator 2 made of formal with a thickness of 25 μm. The strands 1 are twisted into 7×7 pieces, and first arranged in the same manner as a conventional conductor as shown in FIG.

Next, after molding and compressing this stranded wire with a tax roll,
Insulating tape 4 (heat-resistant aromatic polyimide tape) with a thickness of μm is wrapped in a half overlap, and the first
A conductor as shown in the figure was obtained. In the embodiment of FIG.
Compared to the state before molding and compression shown in the figure, the strands 1 are arranged closer to each other, and the proportion occupied by the space 3 is significantly smaller.

A cross-sectional view of the conductor 5 of this embodiment wound around a bobbin 6 of a superconducting magnet is shown in FIG.

For comparison, FIG. 6 shows a state in which the conventional conductor 7 shown in FIG. 5 is similarly wound around the bobbin 6 of a superconducting magnet. As is clear from a comparison of FIGS. 2 and 6, the conductor of this embodiment is small in size and rectangular, so it can be wound densely. therefore,
By using the conductor of this example, a compact superconducting magnet capable of generating a high magnetic field can be manufactured.

In this embodiment, the cross-sectional shape is approximately square, but it goes without saying that the cross-sectional shape is not limited in this invention. It may also be a rectangular stranded wire as shown in FIGS. 3 and 4''.

FIG. 3 shows a structure in which the strands 1 covered with an insulator 2 are arranged in two layers, and FIG. The structure shown is located on both sides of the . Conventionally, in these angle-stranded wires, the strands in the center tend to swell and form a space, but in this invention, the strands in the center are arranged close to each other to reduce the space in the center. Can be done.

The filament diameter of the wire used in this invention is 5 μm
It is preferable that it is below. When cooling the conductor by flowing liquid helium through the space, as in the present invention, if the space is reduced due to molding compression, the contact area with the liquid helium is reduced and the cooling effect is reduced. However, 5μ
If the filament diameter is less than m, the AC loss will be small, so even if the cooling effect of liquid helium is reduced, the magnetic stability of the conductor will not be impaired.

In this embodiment, since formal is used as the material of the insulator, it is easily deformed during molding and compression, and the insulation properties do not deteriorate significantly. However, the insulator used in this invention is not limited to formal, and insulators made of other materials can also be used.

In this embodiment, the material is molded and compressed using a tux roll, but it may also be molded and compressed using a die or other means.

[Effects of the Invention] In the AC superconducting conductor of the present invention, the superconducting strands are arranged close to each other due to molding compression, so the space inside the conductor is significantly smaller than in the past. Therefore, the proportion of the highly rigid metal portion increases, and the rigidity of the conductor itself is significantly increased compared to the conventional conductor. Furthermore, since the superconducting wires are close to each other, the current density is also increased at the same time. Therefore, the superconducting magnet around which the AC superconducting conductor of the present invention is wound can generate a high magnetic field. Furthermore, the superconducting magnet can be made more compact.

Furthermore, since the superconducting conductor of the present invention uses a filament with a small diameter, AC loss is small and stable operation can be achieved even under fluctuating current or AC operation. Since the superconducting conductor of the present invention is a stable conductor even under high-speed excitation, it can be effectively used in large-capacity AC equipment such as superconducting generators, large nuclear fusion coils, and the like.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention. FIG. 2 is a partial sectional view showing a state in which the conductor of the embodiment ρ1 of FIG. 1 is wound around the bobbin of a superconducting magnet. FIG. 3 is a sectional view showing another embodiment of the invention. FIG. 4 is a sectional view showing still another embodiment of the invention. FIG. 5 is a sectional view showing a conventional superconducting AC conductor. FIG. 6 is a partial sectional view showing the conventional conductor of FIG. 5 wound around the bobbin of a superconducting magnet. In the figure, 1 is a superconducting wire, 2 is an insulator, 3 is a space, 4 is an insulating tape, and 5 is a superconducting conductor. Figure 1 Figure 5

Claims (5)

[Claims] (1) A plurality of superconducting strands having ultrafine multifilament filaments and covered with an insulator are twisted together, and the superconducting strands are arranged close to each other by molding compression. A superconducting conductor for alternating current, characterized by: (2) The AC superconducting conductor according to claim 1, wherein the insulator is formal. (3) The AC superconducting conductor according to claim 1 or 2, wherein the ultrafine multifilament filament has a diameter of 5 μm or less. (4) The AC superconducting conductor according to claim 1, 2 or 3, wherein the molding compression is molding compression using a die. (5) The AC superconducting conductor according to claim 1, 2 or 3, wherein the molding compression is molding compression using a tax roll.