JP4172454B2 - Flat cable manufacturing method - Google Patents

Description

  The present invention relates to a flat cable, a superconducting device, and a flat cable manufacturing method, and more particularly to a flat cable, a superconducting device, and a flat cable manufacturing method using an oxide superconductor containing bismuth.

  Superconducting wires (wires) are widely used in superconducting equipment such as superconducting magnets, superconducting fault current limiters, magnetic field generators, superconducting cables, superconducting bus bars, and superconducting coils. The superconducting wire has a tape shape in which a plurality of oxide superconductor filaments are covered with a sheath portion made of metal. The cross section of the superconducting wire has, for example, a width of about 4 mm, a thickness of about 0.2 mm, and an aspect ratio (width / thickness) of about 10-20.

  When a superconducting device using a superconducting wire as described above is used under an alternating current, the superconducting wire is required to have a low AC loss. The main component of this AC loss is hysteresis loss. Based on the Bean model, hysteresis loss is approximately proportional to the product of the magnetic field applied to the superconducting wire, the critical current value of the superconducting wire, and the thickness of the superconducting phase.

  FIG. 9 is a cross-sectional perspective view showing the configuration of a conventional superconducting wire. Referring to FIG. 9, superconducting wire 110 uses only one bismuth-based oxide superconducting wire (elementary wire). The superconducting wire 110 has a form in which a plurality of oxide superconductor filaments 102 are covered with a metal sheath portion 103, and is a tape-shaped multifilamentary wire. In the bismuth-based oxide superconducting wire, each oxide superconductor filament 102 does not behave independently as a superconducting phase, but the entire region 107 in which a plurality of oxide superconductor filaments 102 are formed. Behaves as a superconducting phase. Here, the region 107 is a region obtained by connecting the oxide superconductor filaments 102 present at the outermost periphery of the plurality of oxide superconductor filaments 102 with a line. For this reason, when the magnetic field B is applied in the thickness direction (vertical direction in the figure) of the superconducting wire 110, the “thickness of the superconducting phase” corresponds to the width d of the region 107 in the bismuth-based superconducting wire. Jc represents a critical current value.

  Thus, in a superconducting device (for example, a superconducting magnet) used in a situation where the magnetic field B is applied in the thickness direction of the superconducting wire, the width d of the region 107 is reduced in order to reduce AC loss. Is required. In order to reduce the width d of the region 107, the width w of the superconducting wire 110 itself may be reduced.

In addition, the structure of the conventional oxide superconducting wire is disclosed by Unexamined-Japanese-Patent No. 2004-241254 (patent document 1).
JP 2004-241254 A

  However, if the width of the superconducting wire is narrowed, there is a problem that it is difficult to wind the superconducting wire when manufacturing a superconducting device.

  That is, when the width w of the superconducting wire 110 is reduced, the cross-sectional area of each oxide superconductor filament 102 is reduced, and the critical current value flowing through the oxide superconductor filament 102 is reduced. For this reason, in order to obtain the same performance as the superconducting wire when the width is not narrowed, it is necessary to increase the number of windings of the superconducting wire 110. Therefore, winding of the superconducting wire 110 becomes difficult.

  Also, since the bismuth-based oxide superconducting wire is particularly highly anisotropic magnetic field-dependent, in order to suppress the decrease in the critical current value due to the self-magnetic field, the а-b plane (CuO of CuO) It is necessary to perform winding so that the crystal planes are aligned. Here, “winding so that the а-b faces of the crystal are aligned” means winding so that the direction of the width d of the region 107 is aligned. However, if the width w of the superconducting wire 110 is narrowed, the superconducting wire 110 is easily twisted during winding. Therefore, it is difficult to wind the superconducting wire 110 while aligning the direction of the width d of the region 107.

  Therefore, the objective of this invention is providing the manufacturing method of the flat cable which can reduce alternating current loss, and can be wound easily, a superconducting apparatus, and a flat cable.

  In this specification, a “flat cable” is an aggregate of a plurality of strands, and has a wide (flat) shape when viewed in a cross section perpendicular to the longitudinal direction of the strands. It means a certain aggregate. The wide shape is a shape that is sufficiently longer in the width direction than in the thickness direction.

  The flat cable of the present invention is formed between a plurality of strands having a tape-like form in which an oxide superconductor containing bismuth is covered with a metal, and each of the plurality of strands. And an insulating layer for electrically insulating each other. Each of the plurality of strands is arranged so that the ab planes of the crystals constituting the oxide superconductor are aligned on the same straight line.

The flat cable manufacturing method of the present invention includes a step of manufacturing a plurality of strands having a tape form in which an oxide superconductor containing bismuth is covered with a metal, and a width direction end portion of each of the plurality of strands. A removing step of removing the metal, and a step of forming an insulating layer for electrically insulating each of the plurality of strands between each of the plurality of strands. Each of the plurality of strands is arranged so that the ab planes of the crystals constituting the oxide superconductor are aligned on the same straight line.

According to the flat cable manufacturing method of the present invention, by reducing the width of each of the plurality of strands, the thickness of the superconducting phase is reduced, and the alternating current is applied when a magnetic field is applied in the thickness direction of the flat cable. Loss can be reduced. Further, since the flat cable of the present invention is composed of a plurality of strands, even if the width of each of the plurality of strands is reduced, the critical current value of the entire flat cable is limited to only one strand. It is almost the same as the conventional superconducting wire. Therefore, it is not necessary to increase the number of windings of the flat cable, and it can be easily wound. Furthermore, since the flat cable of the present invention is composed of a plurality of strands, even if the width of each of the plurality of strands is narrowed, it is the same as a conventional superconducting wire composed of only one strand. The width of the flat cable can be secured to the extent. Therefore, the flat cable is hardly twisted, and the flat cable can be easily wound while aligning the direction of the superconducting phase. In addition, the flat cable extends in the width direction of each of the plurality of strands. Moreover, since the removal process which removes the metal of the edge part of the width direction in each strand is provided, since each of several strands can be processed into arbitrary width, the width | variety of a flat cable is easily narrowed Can

  Preferably, in the manufacturing method, the removing step is performed so that the oxide superconductor is not exposed. Thereby, since it becomes difficult for an oxide superconductor to touch external air, deterioration of an oxide superconductor can be prevented.

  In the flat cable of the present invention, preferably, each of the plurality of strands constitutes one row. A plurality of other strands having a tape form in which an oxide superconductor containing bismuth is coated with a metal is further provided. Each of the plurality of strands is arranged so that the ab planes of the crystals constituting the oxide superconductor are aligned on the same straight line, and each of the other plurality of strands constitutes another row Yes. One column and the other column are adjacent to each other in the thickness direction of each of the plurality of strands and the other plurality of strands, and one of the plurality of strands and the other plurality of strands One of them is arranged so that each thickness direction is on the same line. The insulating layer is also formed between each of the other plurality of strands.

  In the flat cable of the present invention, preferably, each of the plurality of strands has a width of 0.2 mm or more and 2 mm or less. By setting each of the plurality of strands to a width of 2 mm or less, AC loss can be effectively reduced. Further, since the thickness of each of the plurality of strands is usually less than 0.2 mm, the width can be made larger than the thickness by setting each of the plurality of strands to a width of 0.2 mm or more. The shape of the tape-shaped strand can be ensured.

  The superconducting device of the present invention is manufactured using the above flat cable. Thereby, it becomes a superconducting apparatus with low AC loss and which can be easily wound.

  According to the flat cable manufacturing method of the present invention, it is possible to manufacture a flat cable that can reduce AC loss and can be easily wound.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a cross-sectional perspective view showing a configuration of a flat cable in Reference Example 1. FIG. As shown in FIG. 1, the flat cable 10 of the present embodiment includes a strand 1 a, a strand 1 b, a strand 1 c, a strand 1 d, and an insulating layer 4. The strands 1a to 1d and the insulating layer 4 have a tape shape and extend in a direction perpendicular to the paper surface. Moreover, each of the strands 1a-1d is arranged so that the width direction (horizontal direction in the figure) of each strand 1a-1d may correspond. The insulating layer 4 is formed between the strands 1a to 1d, and the strands 1a to 1d are electrically insulated from each other by the insulating layer 4. In addition, the area | region 7 enclosed with the dotted line is an area | region which functions as a superconducting phase in the strand 1a, and has the width | variety d.

  FIG. 2 is a cross-sectional perspective view showing the configuration of the wire in FIG. The strand 1 in FIG. 2 is the strands 1a to 1d in FIG. As shown in FIG. 2, the strand 1 has a width w and a thickness t, and has a plurality of oxide superconductor filaments 2 containing bismuth and a metal sheath portion 3 made of, for example, silver. ing. The metal sheath portion 3 covers each of the plurality of oxide superconductor filaments 2. The material of each of the plurality of oxide superconductor filaments 2 has, for example, a Bi—Pb—Sr—Ca—Cu—O composition, and in particular, an atomic ratio of (bismuth and lead): strontium: calcium: copper. Is optimally a material containing a Bi2223 phase represented by an approximate ratio of 2: 2: 2: 3. The crystal composing the oxide superconductor filament 2 extends in the same direction as the ab plane extending in the same direction as the width direction of the strand 1 and the thickness direction (vertical direction in the figure) of the strand 1. C-axis. In the oxide superconductor filament 2, current flows in the ab plane. In addition, it is preferable that the width | variety w of the strand 1 is 0.2 mm or more and 2 mm or less.

  In the above description, the multi-core wire has been described. However, a single-core wire in which one superconductor filament is covered with a sheath portion may be used. Moreover, the number of the strands in a flat cable is not limited to four, What is necessary is just two or more.

  Then, the manufacturing method of the flat cable of this Embodiment is demonstrated.

  First, an element wire 1 having a form in which an oxide superconductor filament 2 containing bismuth is covered with a metal sheath portion 3 as shown in FIG. 2 is manufactured. Specifically, first, raw material powder (precursor) of an oxide superconductor is prepared, and this is filled into a metal tube. The raw material powder of the oxide superconductor is made of a material containing, for example, a Bi2223 phase. As the metal tube, it is preferable to use silver or a silver alloy having high thermal conductivity. Thereby, the heat generated when the superconductor partially causes a quench phenomenon can be quickly removed from the metal tube. Next, the wire is drawn to a desired diameter to produce a single core wire covered with a metal such as silver with the precursor as a core material. Next, many single core wires are bundled and fitted into a metal tube made of a metal such as silver. As a result, a multi-core wire rod (hereinafter sometimes simply referred to as a wire rod) having a large number of raw material powders as a core material is obtained. Next, a wire having a multi-core structure is drawn to a desired diameter to produce a multi-core wire in which the raw material powder is embedded in a sheath portion such as silver. As a result, a multifilamentary wire having a form in which the raw material powder of the oxide superconducting wire is coated with a metal is obtained. Subsequently, the density of the raw material powder is increased by rolling the wire. Next, the wire is heat-treated in a pressurized atmosphere. As a result, an oxide superconducting phase is generated from the raw material powder and becomes an oxide superconductor filament. Through the above manufacturing process, the strand 1 of the oxide superconducting wire shown in FIG. 2 is obtained.

  Next, as shown in FIG. 3, a liquid insulator 4a is applied to both ends of the strand 1 in the width direction (lateral direction in the figure). For example, PVC (polyvinyl chloride) can be used as the insulator 4a. Then, as shown in FIG. 1, many strands 1 which apply | coated the insulator 4a are prepared as strand 1a-1d. Then, for example, the ends of the strands 1a to 1d are bonded to each other via the applied insulator 4a so that the widths d of the strands 1a to 1d are aligned. Thereafter, the insulator 4a is solidified to form the insulating layer 4. The flat cable 10 of this Embodiment is completed according to the above process. In the present embodiment, both ends in the width direction of the strands 1a to 1d are not removed.

  The insulator 4a is not limited to PVC, and other than PVC, for example, a fluororesin, a silicon resin, an organic substance such as vinyl, and an organic substance such as ester can be used. Moreover, the formation method of the insulating layer 4 is arbitrary, and you may apply | coat the insulator 4a to the strand 1 whole. Moreover, you may apply | coat the insulator 4a to the strand 1 by immersing the strand 1 in the liquid insulator 4a.

  For example, when the superconducting magnet 20 is manufactured using the flat cable 10 of the present embodiment, the flat cable 10 is arranged so that the direction of the width d of the region 7 functioning as the superconducting phase is aligned as shown in FIG. Wind it.

  In the flat cable 10 of the present embodiment, the strands 1a to 1d having a form in which the oxide superconductor filament 2 containing bismuth is covered with the metal sheath portion 3 and the strands 1a to 1d are electrically insulated from each other. And an insulating layer 4 for the purpose.

  The method of manufacturing the flat cable 10 of the present embodiment includes a step of manufacturing the strands 1a to 1d having a form in which the oxide superconductor filament 2 containing bismuth is covered with the metal sheath portion 3, and the strands 1a to 1d. Forming an insulating layer 4 for electrically insulating each other.

  According to the flat cable 10 and the manufacturing method thereof according to the present embodiment, by reducing the width w of each of the wires 1a to 1d, the width d of the region 7 functioning as a superconducting phase is reduced. The AC loss when the magnetic field B (FIG. 1) is applied in the thickness direction can be reduced. Moreover, since the flat cable 10 is comprised by several strand 1a-1d, even if each width | variety w of the strands 1a-1d is narrowed, the critical current value as the whole flat cable 10 is one piece. It is almost the same as a conventional superconducting wire composed only of strands. Therefore, it is not necessary to increase the number of windings of the flat cable 10, and it can be easily wound. Further, since the flat cable 10 is composed of the strands 1a to 1d, even if the width w of each of the strands 1a to 1d is narrowed, the conventional superconducting wire composed of only one strand The width of the flat cable can be secured to the same extent. Therefore, the flat cable 10 is not easily twisted, and the flat cable 10 can be easily wound while aligning the direction of the superconducting phase.

  In the flat cable 10 of the present embodiment, the strands 1a to 1d are arranged so that the width directions of the strands 1a to 1d coincide with each other. Thereby, it becomes the flat cable extended in the width direction of strand 1a-1d.

  In the flat cable 10 of the present embodiment, preferably, each of the strands 1a to 1d has a width w of 0.2 mm or more and 2 mm or less. By making each of the strands 1a to 1d have a width w of 2 mm or less, AC loss can be effectively reduced. Moreover, since the thickness t of each of the strands 1a to 1d is usually less than 0.2 mm, the width w is made larger than the thickness t by setting the strands 1a to 1d to a width of 0.2 mm or more. And the shape of the tape-shaped wire can be ensured.

  Superconducting magnet 20 of the present embodiment is manufactured using flat cable 10. Thereby, it becomes a superconducting apparatus with low AC loss and which can be easily wound.

  In the said manufacturing method, the width direction edge part in each of strand 1a-1d is not removed. Thereby, since the oxide superconductor filament 2 does not come into contact with outside air, the deterioration of the oxide superconductor filament 2 can be prevented.

(Embodiment 2)
In Embodiment 1, it showed about the case where the width direction edge part in each of strand 1a-1d is not removed. However, in this invention, the width direction edge part of each strand 1a-1d is removed. This will be described below.

  FIG. 5 is a cross-sectional perspective view showing a method for removing the end portion in the width direction of the strand in Embodiment 2 of the present invention. As shown in FIG. 5, in the present embodiment, after manufacturing the strand 1, each of the width direction end portions 8a and 8b of the strand along the cut lines 5a and 5b or the cut lines 6a and 6b. Remove. Each of the end portions 8a and 8b in the width direction may be removed along the cut lines 6a and 6b where the oxide superconductor filament 2 is exposed, but at a position where the oxide superconductor filament 2 is not exposed. It is preferable to be removed along the cut lines 5a and 5b. Moreover, you may remove only one among the width direction edge parts 8a and 8b of a strand. FIG. 6 shows the state of the strands after the width direction ends 8a and 8b are removed along the cut lines 5a and 5b.

  Since the other flat cable manufacturing method is substantially the same as the manufacturing method of the first embodiment, the same members are denoted by the same reference numerals and description thereof is omitted.

  The flat cable manufacturing method of the present embodiment further includes a removing step of removing the width direction end portions 8a and 8b in each of the strands 1a to 1d. Thereby, since each of the strands 1-1d can be processed into the arbitrary width w, the width | variety of a flat cable can be narrowed easily.

  Preferably, in the above manufacturing method, the width direction end portions 8a and 8b are removed along the cut lines 5a and 5b so that the oxide superconductor filament 2 is not exposed. This makes it difficult for the oxide superconductor filament 2 to come into contact with the outside air, so that deterioration of the oxide superconductor filament 2 can be prevented.

(Embodiment 3)
In Embodiment 1 shown in FIG. 1, the flat cable 10 in which the strands 1 a to 1 d are arranged so that the width directions of the strands 1 a to 1 d coincide with each other is shown. However, the arrangement of the flat cables of the present invention is not limited to such a case.

FIG. 7 is a cross-sectional perspective view showing the configuration of the flat cable in Reference Example 2 . As shown in FIG. 7, in the flat cable 11, the strands 1 a to 1 d are arranged so that the thickness directions (vertical direction in the drawing) of the strands 1 a to 1 d coincide with each other. The insulating layer 4 is formed between the strands 1a to 1d, and the strands 1a to 1d are electrically insulated from each other by the insulating layer 4.

FIG. 8 is a cross-sectional perspective view showing another configuration of the flat cable in Reference Example 3 . As shown in FIG. 8, in the flat cable 12, each of the strands 1a and 1b is arranged such that the thickness direction of the strand 1a (the vertical direction in the drawing) matches the thickness direction of the strand 1b. Are lined up. Each of the strands 1a and 1c is arranged so that the width direction (lateral direction in the drawing) of the strand 1a and the width direction of the strand 1c coincide. Each of the strand 1b and the strand 1d is arranged so that the width direction (lateral direction in the drawing) of the strand 1b coincides with the width direction of the strand 1d. The insulating layer 4 is formed between the strands 1a to 1d, and the strands 1a to 1d are electrically insulated from each other by the insulating layer 4.

  In addition, since the structure of the other flat cables 11 and 12 is substantially the same as the structure of the flat cable 10 of Embodiment 1, the same code | symbol is attached | subjected to the same member and the description is abbreviate | omitted.

Reference Example 2 In the flat cable 11, the strands 1 a to 1 d are arranged so that the thickness directions of the strands 1 a to 1 d coincide with each other. Thereby, it becomes the flat cable extended in each thickness direction of the strands 1a-1d.

  In the flat cable 12 according to the present embodiment, each of the strands 1a to 1d is also arranged so that the width directions of the strands 1a to 1d coincide with each other. Thereby, it becomes the flat cable extended in both the thickness direction and the width direction of each of the strands 1a-1d.

  Examples of the present invention will be described below.

In this example, the AC loss and winding ease of the flat cable of the present invention were examined. Specifically, five types of samples of Comparative Examples A to C, Reference Example 4 and Example of the present invention were produced as follows.

  Comparative Example A: A strand made of a bismuth-based oxide superconducting wire was manufactured by the method shown in the first embodiment. The strands had a width of 5 mm, a thickness of 0.2 mm, a silver ratio of 4, and a twist pitch of 10 mm.

  Comparative Example B: A strand made of a bismuth-based oxide superconducting wire was manufactured by the method shown in the first embodiment. The element wire had a width of 2 mm, a thickness of 0.2 mm, a silver ratio of 4 and a twist pitch of 10 mm, and the width was narrower than that of Comparative Example A.

  Comparative Example C: A strand made of a bismuth-based oxide superconducting wire was manufactured by the method shown in the first embodiment. And the width direction edge part of this strand was removed, it was set as width 1mm and thickness 0.25mm, and the width | variety was made further narrower than the width | variety of the comparative example B.

Reference Example 4 : A strand having the same dimensions as Comparative Example B was produced. Then, PVC insulation was applied to this strand, and it was divided into four equal parts, and two strands were lined up and fused together to produce a flat cable having a width of 5 mm.

Invention Example : A wire having the same dimensions as Comparative Example C was produced. This strand was then subjected to PVC insulation, and was divided into four equal parts, and four strands were aligned and fused to produce a flat cable having a width of 5 mm.

For each of Comparative Examples A to C, Reference Example 4 and Example of the present invention thus obtained, the AC loss in liquid nitrogen was measured using the magnetization method. When measuring AC loss, flat cables were arranged in a straight line, an AC current with a frequency of 50 Hz was passed, and a magnetic field of 0.1 T was applied in the thickness direction of the strands. The alternating current loss per unit critical current value was calculated by dividing the measured alternating current loss per unit superconductor product by the critical current value Ic. Next, assuming that the AC loss per unit critical current value of Comparative Example B was 1, the AC loss per unit critical current value of each sample was normalized and calculated. The critical current value Ic of Comparative Example A is 40A, the critical current value Ic of Comparative Example B is 35A, the critical current value Ic of Comparative Example C is 20A, and the critical current values Ic of Reference Example 4 and the inventive example are both 70A. Met.

Moreover, production of a pancake coil was tried using each of Comparative Examples A to C, Reference Example 4 and the present invention . As the pancake coil, a coil having a winding of 100 turns using a 100 mm diameter winding frame made of FRP (fiber reinforced plastic) was used. And the ease of winding was judged based on whether the pancake coil was able to be produced. Table 1 shows the AC loss per unit critical current value and the winding ease of each sample.

Referring to Table 1, in Comparative Example A in which the strand width is 5 mm, the AC loss is 4, whereas in Comparative Example B, Comparative Example C, and Reference Example 4 in which the strand width is 2 mm or less. In each of the invention examples , the AC loss was 1 or less as compared with the case where the AC loss in Comparative Example B was 1. In particular, the AC loss was 0.5 in Comparative Example C and the inventive example in which the width of the strand was 1 mm. From this, it can be understood that the AC loss can be reduced as the width of the wire is narrower.

Further, in Comparative Example B in which the width of the element wire was 2 mm, winding collapse occurred at the time of winding about 50 turns, and it was difficult to produce a pancake coil. Further, in Comparative Example C where the width of the element wire was 1 mm, winding collapse occurred when winding about 25 turns, and it was difficult to produce a pancake coil. On the other hand, in Comparative Example A, Reference Example 4 and Example of the present invention where the width of the wire or the flat cable was 5 mm, a desired pancake coil could be produced. From this, it can be seen that winding is easier as the width of the wire or flat cable is wider.

Judging comprehensively from the above normalized loss and ease of winding, it can be seen that according to Reference Example 4 and the example of the present invention , the normalized loss is reduced and the winding ease is not lowered. And it turns out that an alternating current loss can be effectively reduced especially by making the width | variety of a flat cable into the width of 2 mm or less.

  The embodiments and examples disclosed above are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown not by the above embodiments and examples but by the scope of claims, and is intended to include all modifications and variations within the meaning and scope equivalent to the scope of claims. .

  The flat cable of the present invention can be used for superconducting equipment such as a superconducting magnet, a superconducting fault current limiter, a magnetic field generator, a superconducting cable, a superconducting bus bar, and a superconducting coil.

It is a cross-sectional perspective view which shows the structure of the flat cable in the reference example 1. FIG. It is a cross-sectional perspective view which shows the structure of the strand in FIG. It is a figure which shows the manufacturing method of the flat cable in the reference example 1. FIG. It is a figure which shows typically a mode that a superconducting magnet is manufactured using the flat cable of the reference example 1. FIG. It is a cross-sectional perspective view which shows the removal method of the width direction edge part of the strand in Embodiment 2 of this invention. It is a fragmentary sectional perspective view which shows the mode of the strand after removing the width direction edge part along a cut line. It is a section perspective view showing the composition of the flat cable in reference example 2 . It is a cross-sectional perspective view which shows the other structure of the flat cable in the reference example 3 . It is a cross-sectional perspective view which shows the structure of the conventional superconducting wire.

Explanation of symbols

    1, 1a to 1d strand, 2,102 oxide superconductor filament, 3,103 metal sheath part, 4 insulating layer, 4a insulator, 5a, 5b, 6a, 6b cut line, 7,107 superconducting phase region, 8a, 8b Width direction end of wire, 10-12 flat cable, 20 superconducting magnet, 110 superconducting wire.

Claims (2)

Producing a plurality of strands having a tape-like form in which an oxide superconductor containing bismuth is coated with a metal;
A removing step of removing the metal at the end in the width direction of each of the plurality of strands;
Forming an insulating layer between each of the plurality of strands for electrically insulating each of the plurality of strands from each other;
Each of the plurality of strands is a flat cable manufacturing method in which the ab planes of crystals constituting the oxide superconductor are aligned on the same straight line. The flat cable manufacturing method according to claim 1 , wherein the removing step is performed such that the oxide superconductor is not exposed.

Images