JP2549695B2 - Superconducting stranded wire and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a superconducting stranded wire having a low AC loss, which is used as a superconducting conductor for a winding of a superconducting generator or a superconducting magnet, and a manufacturing method thereof.

"Prior Art" In a superconducting magnet configured by winding a superconducting wire around a winding drum, when the superconducting wire is energized by being energized, the superconducting wire may move due to a strong electromagnetic force generated. The reason why the superconducting wire moves in this way is that when the superconducting wire is wound around a winding cylinder to form a superconducting coil, a load such as mechanical stress is applied between the turns of the superconducting coil and between layers, It is believed that this is because the superconducting wire moves toward a stable place due to the electromagnetic force generated at. When the superconducting wire moves on the winding cylinder during excitation in this way, the magnetic field generated by the superconducting coil fluctuates, and this magnetic field fluctuation sometimes causes the superconducting wire to quench from the superconducting state to the normal conducting state. It is necessary to firmly fix the superconducting wire so that it will not move because it will cause it.

For this reason, conventionally, after the superconducting wire has been wound around a winding cylinder, the superconducting coil is entirely covered with a low melting point metal such as solder or a resin such as an epoxy resin to fix the superconducting wire.

"Problems to be solved by the invention" However, covering the periphery of a superconducting wire with a substance having a poor thermal conductivity such as an epoxy resin causes a problem of reducing the cooling efficiency of the superconducting wire performed using a refrigerant such as liquid helium. However, it is disadvantageous especially when it is applied as a superconducting twisted wire for alternating current.

The present invention has been made in order to solve the above problems, the fixation of the superconducting twisted wire is strong and reliable, the cooling efficiency by the refrigerant is sufficiently high, and the coupling loss between the superconducting twisted wires can be reduced. An object of the present invention is to provide a superconducting twisted wire and a method for manufacturing the same.

"Means for Solving the Problems" In order to solve the above problems, the present invention provides a fluororesin layer outside the core wire, and around the fluororesin layer, the fluororesin layer is surrounded to twist the superconducting wire. A wire is provided and a part of the superconducting wire is embedded and fixed in a fluororesin layer.

The method of the present invention forms a fluororesin layer on the outside of the core wire, twists the superconducting wire around the fluororesin layer in a softened state by heating the fluororesin layer, and part of the superconducting wire in the fluororesin layer. The method of solving the problem was to embed and cool the stranded wire to cool the superconducting wire with a fluororesin layer.

"Function" The superconducting wire is twisted in the softened state of the fluororesin layer,
A part of the superconducting wire is embedded in the fluororesin layer, and then the fluororesin layer is solidified to fix the superconducting wire. Since the twisted superconducting wire is partially exposed from the fluororesin layer, it can be efficiently cooled by the refrigerant.

"Example" FIG. 1 shows an example of a superconducting stranded wire manufactured by the method of the present invention. The superconducting stranded wire A includes a core wire 1 and a fluororesin layer formed on the outer surface of the core wire 1. 2 and a plurality of superconducting wires 3 which are wound along the outer surface of the fluororesin layer 2 to form a twisted wire. Each superconducting wire 3 is provided outside the fluororesin layer 2 by inserting several tens% or more of the volume into the groove 5 formed on the outer surface of the fluororesin layer 2.

The core wire 1 is compounded for the purpose of reinforcing the superconducting stranded wire A, and one having high mechanical strength such as steel wire, copper wire or various alloy wires is selected. If the superconducting wire 3 used in the present invention has a sufficiently high mechanical strength, the core wire 1 may be formed of the superconducting wire 3.

Further, the fluororesin layer 2 is made of polytetrafluoroethylene, polychlorotriolethylene, polyvinylidene fluoride, a copolymer of tetrafluoroethylene and hexafluoropropylene, etc., and is excellent in electrical insulation.
A material that softens at a temperature of 0 to 400 ° C. is used.

On the other hand, for the superconducting wire 3, it is preferable to use an alloy-based superconducting wire such as NbTi, but if twisted wire processing is possible,
Nb ₃ superconductive intermetallic compound-based superconducting wire, such as Sn, or Y-Ba-Cu-O system, Bi-Sr-Ca-Cu -O system, Tl-Ca-
There is no problem even if an oxide-based superconducting wire typified by Ba-Cu-O system is used.

To manufacture the superconducting stranded wire A shown in FIG. 1, first, a core wire 1 is prepared, and a fluororesin layer 2 having a thickness of about 2 to 3 mm is formed around the core wire 1 by an extrusion molding method, a compression molding method, It is formed by a known method such as an injection molding method or a coating method, and is fired if necessary. After the fluororesin layer 2 is formed, the whole is heated to 200 to 400 ° C. to soften the fluororesin layer 2.
In this state, a plurality of superconducting wires 3 prepared in this state are twisted around the outer circumference of the fluororesin layer 2. These superconducting wires 3
When twisting, the superconducting wire 3 is twisted so that each of the superconducting wires 3 is embedded in the softened fluororesin layer 2 by several tens% or more of its cross-sectional area.
If the superconducting wires 3 are twisted, the adjacent superconducting wires 3, 3
May be tightly wound so that they are in contact with each other, or as shown in FIG. 1, gap winding may be performed in which a gap is formed between the superconducting wires 3 and 3, and the pitch may be any value. .

After the superconducting wires 3 have been twisted, the fluororesin layer 2 is cooled to room temperature and solidified. When the fluororesin layer 2 is solidified, the groove 5 is formed in the portion of the fluororesin layer 2 in which the superconducting wires 3 are embedded, and the superconducting wires 3 are arranged and fixed along the groove 5.

The superconducting stranded wire A thus produced is used for the purpose of winding an insulating tape or the like for insulation treatment, and further winding it around a winding cylinder to form a superconducting magnet.

Since the superconducting twisted wire A has a structure in which the superconducting wires 3 are twisted along the groove 5 formed on the outer surface of the fluororesin layer 2, the superconducting wires 3 ... Even if you try to move in the circumferential direction, you can not move, so you can obtain a highly stable one. Therefore, when a superconducting magnet is formed by using the superconducting twisted wire A having the structure shown in FIG. 1, a strong electromagnetic force does not act due to energization by exciting the superconducting wires 3 ... It is possible to drive. Moreover, since each superconducting wire 3 is projected from the fluororesin layer 2, the cooling medium for cooling the superconducting magnet is satisfactorily spread around the superconducting wires 3 and a sufficient cooling effect can be expected. Therefore, the superconducting stranded wire A
Provides a sufficient cooling effect even when used for AC, and enables highly stable operation even for AC.

Further, since each superconducting wire 3 is insulated by the fluororesin layer 2, it is possible to prevent the coupling current from flowing between the superconducting wires 3 when the superconducting wires 3 are energized. There is an effect that coupling loss can be eliminated.

"Production Example 1" A stainless steel core wire having a diameter of 2 mm was prepared, and a polytetrafluoroethylene layer having a thickness of 1 mm was formed on the outer circumference of the core wire. Next, a NbTi superconducting wire having a diameter of 0.5 mm was provided around the polytetrafluoroethylene layer by heating while heating to 300 ° C. The pitch of the superconducting wires was 20 mm, and the gap winding was such that the interval between the superconducting wires adjacent to each other in the circumferential direction of the core wire was 0.6 mm.

Next, an insulating tape made of polyimide was wound around the outer periphery of the obtained superconducting stranded wire for insulation treatment, and the insulated superconducting stranded wire was wound around a winding cylinder having an outer diameter of 50 mm to obtain a superconducting magnet.

The superconducting magnet manufactured in this manner was cooled with liquid helium, and the superconducting wire was energized to generate a magnetic field of 6T.

As a result of the current-carrying experiment, it was found that the temperature rise in each part of the superconducting wire was not observed, and that each superconducting wire was sufficiently cooled.

"Effects of the Invention" As described above, according to the present invention, a superconducting wire having a structure in which a superconducting wire partially embedded in a fluororesin layer and formed into a stranded wire and having a structure in which the superconducting wire is fixed by the fluororesin layer has high mechanical strength. A stranded wire can be obtained. Therefore, in the superconducting magnet configured by using the superconducting stranded wire of the present invention, there is no possibility that the superconducting wire will move due to the electromagnetic force generated during the excitation, and there is an effect that safer operation can be performed.
Further, since the plurality of twisted superconducting wires are insulated by the fluororesin layer, it is possible to prevent the coupling current that tends to occur between the superconducting wires and eliminate the coupling loss. be able to. Furthermore, since a part of the outer peripheral portion of the superconducting wire projects from the fluororesin layer, it can be cooled at a sufficiently high rate when cooling the superconducting wire with a refrigerant, and it can also be used for alternating current. There is an effect that can be done.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a superconducting stranded wire manufactured by carrying out the present invention. A ... Superconducting twisted wire, 1 ... Core wire, 2 ... Fluorine resin layer,
3 ... Superconducting wire, 5 ... Groove.

Claims (2)

(57) [Claims] 1. A fluororesin layer is provided outside a core wire, and a plurality of superconducting wires are twisted by surrounding the fluororesin layer around the fluororesin layer, and a part of the superconducting wires is fluororesin. Superconducting stranded wire characterized by being buried in layers. 2. A fluororesin layer is formed on the outside of a core wire, and the superconducting wire is twisted around the fluororesin layer while being heated and softened, and a part of the superconducting wire is embedded in the fluororesin layer. In addition, the method for producing a superconducting twisted wire is characterized in that the superconducting wire is fixed by a fluororesin layer after cooling the twisted wire.