JPH07192548A - Superconductive conductor - Google Patents

Abstract

PURPOSE:To manufacture a highly stable superconductive conductor by skip- winding the outer peripheries of tertiary and quadratic stranded wires with an electric insulation thin wall tape to constitute a stranded wire in a cable-in- conduit type forced cooling conductor. CONSTITUTION:Three primary stranded wires, wherein three superconductive raw materials 11 are twisted, are twisted to form a secondary stranded wire 12, and moreover three secondary stranded wires 12 are twisted to form a tertiary stranded wire 13. An electrical insulation thin wall tape or foil 14 is spirally skip-wound along a longitudinal direction on the outer periphery of the tertiary stranded wire 13, and moreover three tertiary stranded wires 13 are twisted to form a quadratic stranded wire 15. wed Similarly, the thin wall tape 14 is skip-wound on the quadratic stranded wire 15, and some of the quadratic stranded wires 15 are bundled to be adopted as stranded wires to constitute the final stranded wire. Then 6 final stranded wires are twisted to be housed in a conduit 16 to be die-drawn to a given void ratio, manufacturing a superconductive conductor 18. This can provide the superconductive conductor 18 to a low void ratio so that the superconductive raw wire 11 in the conduit 16 can not be moved by electromagnetic force.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cable in which a plurality of superconducting wires are twisted together and housed in an outer tube, and a refrigerant is flown in a space between the superconducting wires and a space between the superconducting wire and the outer tube.
The present invention relates to a superconducting conductor in which AC loss of a conduit type forced cooling conductor is reduced and superconducting stability is improved.

[0002]

2. Description of the Related Art A forced cooling type superconducting conductor that cools by using forced convection of a single-phase flow such as supercritical helium or a cryogenic fluid is a hollow conductor, a cable-in-conduit conductor, or a combination thereof. There is a conductor.

The hollow conductor is constructed so that a large number of ultrafine multi-core superconducting wires are gathered together and integrated with a stabilizing material such as solder, and a hole is made in the central portion thereof so that helium as a refrigerant can be fed under pressure.

Also, the cable-in-conduit conductor 8
Are configured as shown in FIG. That is, first, several (three in the figure) superconducting strands 1 of Nb Ti or Nb ₃ Sn, which are ultra-fine multi-core, are twisted together to form a primary stranded wire 2, and the primary stranded wire 2 is stranded three by three. A secondary twisted wire 3 is made together, and further, a third twisted wire 4, a fourth twisted wire 5, and a final twisted wire are multi-twisted into a cable shape and made of SUS material, incoloy material, Ti material or alloys thereof. Strong conduit
It is configured so that the refrigerant flows in a space 7 which is housed inside 6 and surrounded by the inner wall of the conduit 6 other than the superconducting element wire.
(See US Pat. No. 4,336,420: Jun. 22,1982).

This kind of superconducting conductor is designed so that the coupling loss and hysteresis loss in one superconducting element wire generated under a varying magnetic field are minimized. Further, in order to reduce the coupling loss between the superconducting element wires due to the twisted wire structure, the surface of the superconducting element wires is generally provided with a high resistance coating having high electrical insulation such as formal or chrome.

[0006]

In the conventional cable-in-conduit conductor 8 of a superconducting conductor, the superconducting wire 1 in the conduit 6 moves in the conduit 6 by an electromagnetic force to generate heat and the wire temperature rises. Then, when the superconducting destruction (quenching) is partially performed, the current of the quenched superconducting element wire is redistributed to the surrounding superconducting element wires 1 in an attempt to suppress the quenching phenomenon. Since the surface of the strand 1 is coated with a high resistance material having high electrical insulation, redistribution of current is excluded, and only a low current can flow. In addition, when the current is unevenly distributed at the end of the conductor, there is a drawback that the uniformity of the current distribution due to the current redistribution between the twisted wires is hindered and the stability is lowered. Further, there is a defect that the high resistance coating having a high electric insulation property on the surface of the strand becomes a resistor also in terms of heat and causes a remarkable decrease in heat removal characteristics.

As a method for solving the above-mentioned drawbacks, the coupling loss and hysteresis loss in the wire are designed to be as small as possible, and the surface of the wire is electrically insulative so that the redistribution of current is not excluded. Although a conductor without a high resistance coating has been proposed, it has a drawback that the coupling loss between the twisted wires rapidly increases and thus the stability under a fluctuating magnetic field significantly decreases.

Also, in order to prevent quenching due to the movement of the strands, an adhesive is applied to the outer circumference of the superconducting strands and adhered to each other (see Japanese Patent Laid-Open No. 2-297808). A spiral wound thermosetting insulating tape has been proposed (see Japanese Patent Application Laid-Open No. 4-17293), but there is no coupling loss in the wires, but the redistribution of current is alienated. The drawback of being done is not ameliorated.

The present invention has been made in order to solve the above-mentioned drawbacks, and an object thereof is to reduce the AC loss under a changing magnetic field, and to make the current redistribution characteristics at the time of quenching good, in which current drift is less likely to occur. It is to provide a superconducting conductor with high stability that is maintained at.

[0010]

In order to achieve the above object, the first aspect of the present invention is that a plurality of metal alloy or compound superconducting wires having no surface electrical insulation are twisted in multiple layers. In a cable-in-conduit type forced cooling conductor that stores a refrigerant in the outer tube and flows a refrigerant into the space between the superconducting wires and the space between the superconducting wire and the outer tube, electrical insulation is provided on the outer circumference of the third twisted wire or the fourth twisted wire. It is characterized in that it is formed by wrapping it with a thin tape that is wound around to form a stranded wire, housed in a conduit, and compression molded to a predetermined porosity.

A second aspect of the invention is characterized in that a thin tape or foil having high electric insulation and high thermal conductivity is used. Further, a third aspect of the present invention is characterized in that a material having high electric insulation and high thermal conductivity is discontinuously coated on the surface of the stranded wire in the conductor longitudinal direction.

[0012]

According to the superconducting conductor of the present invention, the electrical connection in the conductor cross section is insulated for each small block to reduce the AC loss under a varying magnetic field and to have a high electric insulation and a thermal conductivity. Highly conductive material is electrically connected discontinuously in the longitudinal direction of the conductor on the surface of the stranded wire, so current drift is less likely to occur and excellent superconducting stability can be obtained, such as maintaining good current redistribution characteristics during quenching. .

[0013]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a cross-sectional view of an embodiment of the present invention. In FIG. 1, 11 is a superconducting element wire, and Nb Ti or Nb ₃ Sn ultrafine multi-core superconducting wire is surrounded by a stabilizing material such as Cu or Al. , Further insert electrical insulation if necessary. As shown in FIG. 2, this superconducting element wire 11 is formed by twisting three primary stranded wires, each of which is twisted into three, to form a secondary stranded wire 12. The secondary twisted wire 12 is further twisted three times to form a tertiary twisted wire 13. This tertiary stranded wire 13
An electrically insulating thin tape such as Cu Ni or a foil 14 is spirally wound around the outer circumference of the foil along the longitudinal direction. In this way, the third stranded wire having the insulating thin tape 14 applied to the outer periphery is further twisted into three to form a quaternary stranded wire 15. An electrically insulating thin tape 14 is also wound around the outer periphery of the fourth twisted wire 15 in a spiral shape along the longitudinal direction. Furthermore, several quaternary twisted wires 15 are twisted together to form the final twisted wire.

In this embodiment, six twisted wires are used to form the conduit 16
Stored in a superconducting conductor by dicing to a specified porosity.
Produce 18. Furthermore, the electrically insulating thin tape 14 wound around the outer circumferences of the third twisted wire 13 and the fourth twisted wire 15 does not bind the twisted wires firmly at each twisted wire stage, and has an excessive size between the twisted wires in the final shape. A superconducting conductor 18 is manufactured by dicing to a low void rate so that the superconducting element wire 11 in the conduit 16 does not move due to an electromagnetic force.

In the case of the superconducting element wire 11 using the compound-type superconducting wire Nb ₃ Sn, the superconducting material is produced by heat treatment after dicing in order to prevent deterioration of the superconducting characteristics due to dicing. Further, instead of winding the electrically insulating thin tape 14 in a spiral shape along the longitudinal direction and winding it, after non-coating film treatment is performed discontinuously in the longitudinal direction, for example, high electrical insulating property such as aluminum nitride, Tertiary stranded wire 13 and quaternary stranded wire with high thermal conductivity material or ceramic material
A coating film may be formed on the outer periphery of 15.

By electrically insulating the coupling between the twisted wires at the stage of the third twisted wire 13 and the fourth twisted wire 15, the coupling loss under an alternating magnetic field can be greatly reduced. In addition, since the conductor is skipped and wound in the longitudinal direction, electrical coupling occurs between twisted wires that are not wound with the electrically insulating thin tape 14, and a coupling loss occurs, but on the other hand, the current drift phenomenon is suppressed. In addition, the current redistribution during the quench can be improved. Therefore, it has high superconducting stability.

[0017]

As described above, according to the present invention, a superconducting material having a high stability, which can reduce the AC loss under a fluctuating magnetic field, hardly cause a current drift, and keep a good current redistribution characteristic at the time of quenching. A conductor can be provided.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is an enlarged perspective view of the fourth stranded wire of FIG.

FIG. 3 is a view showing a manufacturing process of a conventional superconducting conductor.

[Explanation of symbols]

1, 11 ... Superconducting wire, 2 ... Primary stranded wire, 3, 12 ... Secondary stranded wire, 4, 13 ... Tertiary stranded wire, 5, 15 ... Quaternary stranded wire, 6, 16 ... Conduit, 7, 17 ... Space, 8 ... Cable-in-conduit conductor, 14 ... Electrically insulating thin tape, 18 ... Superconducting conductor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takataro Hamashima 2-4 Suehiro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa Toshiba Keihin Office

Claims (3)

[Claims] 1. A plurality of metal alloy-based or compound-based superconducting wires that are not electrically insulated on the surface are twisted in multiple layers and housed in an outer tube, and a space between the superconducting wires and the superconducting wire and the outer tube are provided. In a cable-in-conduit type forced cooling conductor that causes a refrigerant to flow in the space, the twisted wire is formed by winding it around the outer circumference of the tertiary stranded wire or the quaternary stranded wire with an electrically insulating thin tape and stored in the conduit. Then, the superconducting conductor is characterized in that it is formed by compression molding to a predetermined porosity. 2. The superconducting conductor according to claim 1, wherein a thin tape or foil having high electric insulation and high thermal conductivity is used. 3. The superconducting conductor according to claim 1, wherein a material having high electric insulation and high thermal conductivity is coated discontinuously in the conductor longitudinal direction on the surface of the stranded wire.