JP4757985B2 - Superconducting coil, manufacturing method thereof and superconducting conductor used therefor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a superconducting coil used for a power storage device, a transformer, a semiconductor single crystal pulling device, a current limiter, an MRI and the like, a manufacturing method thereof, and a superconducting conductor used therefor.
[0002]
[Prior art]
Power equipment using superconductivity has features such as high efficiency and space saving, and research and development for practical use is being promoted. Superconductors are not only liquid helium temperatures (4.2K), but metal-based low-temperature superconductors that operate only in the vicinity of the liquid helium temperature (4.2K). Because it can be used in the temperature range of conduction cooling by the machine (about 20K), supercooled liquid nitrogen temperature (66K), liquid nitrogen temperature (77K) or higher, it can be used for power equipment due to its economic efficiency and ease of handling. The application of is expected.
[0003]
An example of the structure of the superconducting conductor is shown in FIG. In the figure, (a) is a rectangular forming strand called a Rutherford cable formed by twisting strands 21 and formed into a flat shape, and (b) is a rectangular forming strand 23 in a portal reinforcement 22 such as Cu. And (c) is a cable-in-conduit conductor in which a strand 21 is accommodated in a conduit 25 such as stainless steel, and (d) is a primary in which the strand 21 is twisted. A multi-strand wire conductor in which a stranded wire 28 is wound around a small-diameter reinforcing wire 27 and a secondary stranded wire 28 is arranged around a large-diameter reinforcing wire 29, and (e) is a laminate of a plurality of tape-like wires 30. The parallel conductor (f) is a concentric circular wire conductor in which the tape-shaped wires 30 are concentrically arranged around the circular conduit 31.
[0004]
Among such conductors, the conductors of FIGS. 7C, 7D, and 7F have no characteristic directivity with respect to the direction of the transverse magnetic field applied from the outside, but (a), (b), The conductor (e) has directionality. In addition, all conductors except (e) are partially or wholly processed, and (c), (d), and (f) are regularly twisted around the conductor axis. Can also be seen.
[0005]
By the way, the transverse magnetic field applied perpendicularly to the wide surface of the Bi2223 tape wire used for the winding of the high-temperature superconducting coil (the magnetic field parallel to the axis is called the longitudinal magnetic field, and is distinguished from this) is the maximum conduction current of the coil, the so-called critical current. The current performance is that the coil performance (maximum output magnetic field and maximum storage energy) is kept low due to the phenomenon of deterioration (hereinafter referred to as “perpendicular magnetic field conduction characteristic deterioration phenomenon”).
[0006]
Also, not only Bi2223 tape wire, but also Y123 tape wire, Tl 1223 tape wire, Nb ₃ Sn tape wire, etc. Under a magnetic field perpendicular to the wide surface of the tape or flat-shaped wire, depending on the conditions, a hysteresis loss or coupling loss that is 1 to 5 orders of magnitude greater is generated than in the case of a transverse magnetic field parallel to the wide surface. ing.
[0007]
As countermeasures against the deterioration phenomenon of the vertical magnetic field energization characteristics of the high temperature superconducting coil, it is most effective to increase the amount of the superconducting material in the wire or increase the number of the wire in the conductor. This increases the total amount of superconducting material and increases costs. In order to eliminate this as much as possible, it is considered that the “grading technology” that has been conventionally used for metal-based low-temperature superconducting coils is relatively effective. This is intended to minimize the amount of superconducting material by locally adjusting the amount of wire only by a necessary amount or by a necessary amount.
[0008]
However, as in the example of finite length solenoid shown in FIG. 1, the vertical magnetic field generally, to become larger at end portions of the coil 10, etc. will be reinforced by that part by the gray de Ingu technique, complex coil structure With difficulty in manufacturing technology. Also, in special applications, such as superconducting transformers, a relatively low magnetic field is used, and an iron core is placed in the center of the coil, so that the vertical magnetic field conduction characteristic deterioration phenomenon does not occur.
[0009]
However, in general applications, because of the high generated magnetic field, the magnetic flux density in the iron core is saturated, so that the iron core cannot be inserted. Even if an iron core can be inserted, the hysteresis loss and eddy current loss additionally generated in the iron core become large and become a problem. Development of a high-temperature superconducting round cross-section wire with uniform characteristics regardless of the direction of magnetic field is also under development, but performance beyond that of a tape wire cannot be obtained.
[0010]
Rutherford cable, which is a typical rectangular wire conductor, was developed for superconducting high-energy accelerators and is used as a winding for dipole magnets that are the main components of accelerators. Taking a dipole magnet as an example, the uniformity of the magnetic field on the long axis of the center of the magnet on which particles such as electrons run is given the highest priority at both ends of a magnet having a length of several meters. Therefore, the Rutherford cable is wound along a three-dimensionally processed spacer. The Rutherford cable will then have a slight twist about its axis.
[0011]
However, the twist is a result of the winding process, and the effect cannot be predicted.
[0012]
[Problems to be solved by the invention]
The problem to be solved by the present invention is that the vertical magnetic field conduction characteristic deterioration phenomenon of the high-temperature superconducting coil due to the magnetic field perpendicular to the coil axis generated at the end of the superconducting coil and the magnetic field applied from other coils, high temperature and The superconducting coil, its manufacturing method, and the solution to the problem of increasing the loss of the low-temperature superconducting coil without complicating the structure of the coil, wire and conductor and reducing the amount of superconducting wire and conductor It is to provide a superconducting conductor to be used.
[0013]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the superconducting coil of the present invention is a conductor having a directivity with respect to a transverse magnetic field to which an energization characteristic or loss characteristic is applied from the outside , and one or more superconducting wires are used. A superconducting coil in which a conductor having a current- carrying part and a conductor containing the current-carrying part are wound, and the current-carrying part together with the conduit having a circular or polygonal cross-sectional shape that can be wound while being twisted The current-carrying characteristic or the loss characteristic with respect to the direction of the transverse magnetic field at each winding position is obtained by twisting the current-carrying portion with respect to the conduit having a cross-sectional outer shape that can be wound without twisting or twisting. There are the conducting portion is given a twist so that the direction of the conductor in a direction in which the best substantially coincides, characterized in that the conductor is wound.
[0014]
Here, the “current-carrying part” refers to a part including one or a plurality of superconducting wires and a part of a stabilizing material or a structural material.
[0015]
There are the following two methods for manufacturing the superconducting coil.
[0016]
(1) When the conductor is wound around the winding frame of the superconducting coil , the conductor supply section is arranged so that the current-carrying characteristics or the loss characteristics substantially coincide with the direction of the transverse magnetic field at each winding position. The conductor is wound while twisting about the central axis of the conductor.
[0017]
In this case, as can be easily winding process while controlling the twisting of the conduit against the central axis of the conduit, the outer shape of the cross section of the conduit is a circular shape or polygonal may winding process while twisting, as stress twisting applied to the outer peripheral surface of the conduit is transmitted securely to the inside of the superconducting wire mechanically integrated and a conduit placed around the superconducting wire it from the inside of the superconducting wire.
[0018]
(2) Before winding the conductor on the winding frame of the superconducting coil, in a state after being wound, it is substantially coincided with the direction in which the current-carrying characteristics or loss characteristics are best with respect to the direction of the transverse magnetic field at each winding position as will be let you provide twist to said conduit about the central axis of advance its conductive portion to the conductive portion, winding the conductor on the spool.
[0019]
In this case, in order to simplify the winding work process as much as possible and to improve the adhesion between the windings of the coil winding portion, the conduit has a cross-sectional outer shape that can be wound without applying twist, such as a circular shape. It is assumed that it has a polygon such as a rectangle, and the superconducting wire is twisted with respect to the conduit in consideration of the pre-calculated magnetic field application direction before integrating the superconducting wire and the surrounding conduit. Use. In that case, a normal winding method that does not give twist during winding can be employed.
[0020]
Furthermore, the superconducting conductor used in the superconducting coil of the present invention is a conductor having a direction characteristic with respect to a transverse magnetic field applied with an energization characteristic or loss characteristic from the outside, and includes one or more superconducting wires. A conductor having a current-carrying part and a conduit containing the current-carrying part, wherein only the current-carrying part of the conductor or the entire conductor including the conduit is twisted with respect to the central axis of the conductor. In the state where the conductor is wound around the winding frame of the superconducting coil, the current-carrying part is in the direction in which the current-carrying characteristic or loss characteristic is the best with respect to the direction of the transverse magnetic field at each winding position. It changes in the longitudinal direction of the said conductor so that it may substantially correspond .
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings, taking as an example a superconducting conductor in which Bi2223 tape wires are laminated.
[0022]
FIG. 2 is an example of the conductor 11. In this example, 28 Bi2223 tape wires 1 are stacked and accommodated in a circular conduit 3, and the tape wires 1 are electrically separated from each other by an intervening tape 2 made of an insulator or a high-resistance metal. The dislocation is performed in order to make the energization current between the tape wires 1 uniform. Here, assuming that the individual tape width is 3.5 mm and the tape thickness is 0.25 mm, approximately 50 mm is required for the dislocation per one piece, so that the total dislocation requires approximately 1.4 m. The outer shape of the conductor 11 is circular, and the outer diameter is about 10 mm. Consider a solenoid coil as shown in FIG. 3 that is wound using this conductor 11 and has an average diameter of 820 mm, a coil length of 760 mm, and a coil winding portion thickness of 180 mm. The total dislocation length of 1.4 m corresponds to about 0.5 turns of coil. The conductor of the central portion of the coil 10 has a magnetic field direction parallel to the coil axis (see FIG. 1), so that the wide surface of the tape wire 1 is parallel to the transverse magnetic field direction as shown in FIG. At the end of the coil 10, the direction of the magnetic field is inclined with respect to the coil axis as shown in FIG. 1, so that the direction of the transverse magnetic field is as shown in FIGS. 3 (b) and 3 (c). The tape wire 1 is twisted and wound obliquely so that the wide surfaces are parallel. Since the direction of the magnetic field gradually changes in the middle, the conductor 11 is also wound so as to be gradually inclined.
[0023]
FIG. 6 shows an example of a method of winding the coil winding around the coil winding frame. In the figure, 12 is a coil winding frame, 13 is a coil winding core, and 14 is a conductor winding frame. When winding the conductor 11 around the coil winding frame 12, the coil 11 is tilted within a range of ± 90 degrees so that the conductor 11 is twisted by a predetermined angle according to the position of the conductor 11 on the coil. When wound on the winding frame 12, the coil 10 shown in FIG. 3 can be obtained.
[0024]
When a coil having this shape is used at 20K, when the maximum energization current of the coil is 2.5 kA, the maximum magnetic field in the coil axis direction at the winding portion is 4T, and the maximum magnetic field in the coil radial direction is 2.5T. The magnetic field dependence of the critical current of one Bi2223 tape wire is shown in FIG. When a 2.5 T transverse magnetic field is applied perpendicularly to the wide tape surface, 90 A flows per tape, whereas when a 4 T transverse magnetic field is applied in parallel to the wide tape surface, it increases by 56% to 140 A. With 28 tapes, the former is 2.5 kA and the latter is 3.9 kA, an increase of 56%. Therefore, as illustrated in FIG. 3, the maximum energization current 2 of the coil is obtained by making the magnetic field direction of the coil winding portion substantially coincide with a specific direction of the conductor cross section (here, parallel to the internal tape wide surface). If the change of 0.5 kA is not changed, the number of tape wires used can be reduced by 36%.
[0025]
Next, consider using this coil at 66K. As shown in FIG. 5, the difference in critical current characteristics between the case perpendicular to the tape wide surface and the case parallel to the tape wide surface becomes more remarkable than 20K. The maximum coil current is 0.45 kA, the maximum transverse magnetic field applied in parallel to the wide tape surface is 0.7 T, and the maximum magnetic field applied perpendicular to the wide surface is 0.4 T. At this time, from FIG. 5, the critical current value of one tape is 42A when a parallel transverse magnetic field 0.7T is applied, and 16A when a perpendicular transverse magnetic field 0.4T is applied. With 28 tapes, the latter is 0.45 kA, and the former is 2.6 times 1.2 kA. Therefore, as illustrated in FIG. 3, by making the magnetic field direction of the coil winding portion substantially coincide with a specific direction of the conductor cross section (here, parallel to the tape wide surface inside), the maximum energization current 0 of the coil is reduced. If the change of .45 kA is not changed, the number of tape wires used can be reduced by 62%.
[0026]
Further, the loss can be locally reduced by one digit or more depending on the position of the coil winding in the coil in both cases of 20K and 66K. Therefore, the loss can be reduced to a fraction of the entire coil.
[0027]
In the case of Y123 or Tl 1223 tape wire, an improvement in the critical current value can be expected, but the loss reduction effect is particularly remarkable. This is because in the Y123 tape wire, the superconducting material Y123 is formed into a film having a thickness of 1 to 10 microns, and the aspect ratio of the superconducting material portion in the wire cross section is about three digits. Therefore, when the direction of the transverse magnetic field is parallel to the tape surface, the loss is about three orders of magnitude smaller than when it is perpendicular.
[0028]
Consider a superconducting conductor composed of one or more stranded wires, or a coil wound with a superconducting conductor including a part thereof. The shape of the coil is the same as that shown in FIG. As shown in FIG. 8, when there are a plurality of rectangular formed strands 23 in the superconducting conductor, they are laminated so that their wide surfaces are aligned with each other. A direction parallel to the wide surface 23 is a “specific direction” of the conductor. The specific direction of the conductor and the direction of the generated magnetic field in the coil winding portion are substantially matched. As a result, a transverse magnetic field in a direction parallel to the wide surface is applied to the internal rectangular forming strand, and a large inter-element coupling loss generated when applied in a direction perpendicular to the wide surface is generated. It can be made extremely small. According to conventional research, the coupling loss can be easily reduced by an order of magnitude. Or, depending on the structure of the conductor, it can be further reduced by one to three digits. In FIG. 8, 24 is a stabilizing material, and 32 is a structural material. In this example, eddy current loss generated in the stabilizing material 24 or the structural material 32 is also applied because a transverse magnetic field parallel to the wide surface is applied. It is made small.
[0029]
【The invention's effect】
According to the present invention, when a coil is wound with a superconducting wire or a superconducting conductor that can be expected to have excellent performance in current-carrying characteristics or loss characteristics when a magnetic field is applied in a specific direction of the cross section of the superconducting wire or superconducting conductor, By applying an appropriate twist around the conductor axis before winding, the direction of the external transverse magnetic field applied to the wire or conductor can be made to substantially match the specific direction of the conductor cross-section, and the performance of the coil is dramatically improved. To increase.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing the direction and strength of lines of magnetic force generated by a superconducting coil.
FIG. 2 is a perspective view showing an example of a conductor.
FIG. 3 is a perspective view showing an example of a coil winding.
FIG. 4 is a critical current characteristic graph of Bi2223 tape wire at 20K.
FIG. 5 is a critical current characteristic graph of Bi2223 tape wire at 66K.
FIG. 6 is a perspective view showing an example of a method of winding a conductor while twisting a coil.
FIG. 7 is a cross-sectional view showing an example of a general conductor structure.
FIG. 8 is a cross-sectional view showing another example of a conductor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Tape wire material, 2 Intervening tape, 3 Conduit, 10 Coil, 11 Conductor, 12 Coil winding frame, 13 Coil winding core, 14 Conductor winding frame, 21 Strand, 22 Gate-shaped reinforcement, 23 Flat wire, 24 Stabilizing material, 25 Conduit, 26 Primary strand, 27 Small diameter reinforcing wire, 28 Secondary strand, 29 Large diameter reinforcing wire, 30 Tape strand, 31 Circular conduit, 32 Structural material

Claims (4)

Conductor or loss characteristic is a conductor having a directivity with respect to a transverse magnetic field applied from the outside, and has a current-carrying part including one or more superconducting wires and a conduit containing the current-carrying part. A superconducting coil wound with a conductor,
The current-carrying part is twisted together with the conduit having a circular or polygonal cross-sectional shape that can be wound while being twisted, or the current-carrying part is twisted with respect to the conduit having a cross-sectional shape that can be wound without applying twist. In each winding position, the energization part is twisted so that the direction of the conductor substantially matches the direction in which the energization characteristic or loss characteristic is the best with respect to the direction of the transverse magnetic field, A superconducting coil in which a conductor is wound. Conductor or loss characteristic is a conductor having a directivity with respect to a transverse magnetic field applied from the outside, and has a current-carrying part including one or more superconducting wires and a conduit containing the current-carrying part. A method of manufacturing a superconducting coil in which a conductor is wound,
The conduit has a circular or polygonal cross-sectional outline that can be wound while being twisted,
When winding the conductor around the winding frame of the superconducting coil, at each winding position, the conductor is substantially aligned with the direction in which the current-carrying characteristic or loss characteristic is best with respect to the direction of the transverse magnetic field. A method of manufacturing a superconducting coil, wherein the conductor is wound while twisting the supply portion about the central axis of the conductor. Conductor or loss characteristic is a conductor that has directivity with respect to a lateral magnetic field applied from the outside, and has a current-carrying part including one or more superconducting wires and a conduit that houses the current-carrying part. A method of manufacturing a superconducting coil in which a conductor is wound,
The conduit has a cross-sectional outer shape that can be wound without giving twist,
Before winding the conductor around the winding frame of the superconducting coil, the energized portion in a state after being wound is in a direction in which the energization characteristic or loss characteristic is the best with respect to the direction of the transverse magnetic field at each winding position. A superconducting coil manufacturing method, characterized in that the current-carrying part is previously twisted with respect to the conduit about the central axis of the current-carrying part, and the conductor is wound around the winding frame so as to substantially match . Conductor or loss characteristic is a conductor having a directivity with respect to a transverse magnetic field applied from the outside, and has a current-carrying part including one or more superconducting wires and a conduit containing the current-carrying part. A conductor,
Only the current-carrying portion of the conductor or the entire conductor including the conduit is twisted about the central axis of the conductor, and the twist is a state after the conductor is wound around the winding frame of the superconducting coil Then, the current-carrying portion changes in the longitudinal direction of the conductor so that the current-carrying characteristic or loss characteristic substantially coincides with the direction of the transverse magnetic field at each winding position. A superconducting conductor used for a superconducting coil.

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