Superconducting wire and cable

Abstract

To provide a superconducting wire and a superconducting cable which combine a reduction of AC loss and an improvement of robustness.SOLUTION: A superconducting wire 10A comprises a plurality of superconducting layers 2 extending in a longitudinal direction of a substrate 1 and placed in parallel in a short direction of the substrate 1, an insulation part 3 extending in a longitudinal direction of the substrate 1, placed between the plurality of superconducting layers 2,2 and electrically insulating the plurality of superconducting layers 2, 2, and a plurality of connection parts 4 placed at the insulation parts 3 along the longitudinal direction of the substrate 1 and superconductively and electrically connecting adjacent plurality of superconducting layers 2, 2, and the following conditions are satisfied by spirally winding. Here, D is a diameter of a spiral, P is a length of a spiral pitch along a winding axis direction, and L is a length of the insulating part 3 along the longitudinal direction.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a superconducting wire and a superconducting cable. [Background technology]

[0002] High-temperature superconductivity has been attracting attention as a technology for efficiently generating, transmitting, converting, using, and storing electrical energy. For example, by using wires made of high-temperature superconducting materials (hereinafter referred to as high-temperature superconducting wires) or superconducting cables made by assembling them in the armature windings of generators and electric motors, it becomes possible to pass a large current through the armature windings. This makes it possible to reduce the armature core, and is expected to reduce the weight of generators and electric motors. If it becomes possible to reduce the weight of generators and electric motors, this will lead to, for example, the realization of the electrification of aircraft and the promotion of the introduction of large floating offshore wind power generation. If the electrification of aircraft is realized and the introduction of wind power generation is promoted, it is expected that CO2 emissions will be reduced, and therefore high-temperature superconductivity technology is expected to greatly contribute to the realization of a low-carbon society.

[0003] On the other hand, when superconducting wire is used with an alternating current, an alternating current magnetic field generates an alternating current loss. In general, when a current flows through a superconductor or a magnetic field is applied, magnetic flux penetrates the superconductor in the form of magnetic flux quanta. Under operating conditions where a direct current or a direct current magnetic field is applied, the magnetic flux quanta do not move and remain stationary, but under operating conditions where an alternating current or an alternating current magnetic field is applied, the magnetic flux quanta must move due to a change in the distribution of magnetic flux at the position of the superconductor. When the magnetic flux quanta move, something like friction occurs, and the equivalent of this frictional heat is the AC loss.

[0004] Furthermore, when a superconducting wire is used in a superconducting state, a phenomenon called a quench may occur for some reason. When a quench occurs, the superconducting wire leaves the superconducting state and transitions to a normal conducting state, causing generators, motors, and other equipment that uses the superconducting wire or cable to stop functioning, and in the worst case scenario, the equipment may be damaged.

[0005] The existence of AC losses in superconducting wires and cables and the low robustness of superconducting wires and cables against quenching are bottlenecks in the social implementation of devices using high-temperature superconductivity. To solve these technical problems related to superconducting wires and cables, various methods have been proposed. For example, Patent Document 1 discloses a high-temperature superconductor that reduces AC losses. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2013-535083 Summary of the Invention [Problem to be solved by the invention]

[0007] 11 and 12 are schematic diagrams for explaining technical problems associated with a superconducting wire 90 according to the conventional technology.

[0008] In the superconducting wire 90A (90) shown in FIG. 11(A), a superconducting layer 92 is uniformly formed on the surface of a substrate 91. AC loss is the work required to move a magnetic flux quantum 93, and the longer the moving distance of the magnetic flux quantum 93, the greater the AC loss. In the superconducting wire 90A (90), the width w t Since the magnetic flux quantum 93 moves across half of the width w, the AC loss becomes large. Reference numeral 94 indicates the movement (penetration) of the magnetic flux quantum 93. In contrast, as shown in FIG. 11(B), when the superconducting layer 92 is formed with a width w f (<width w t) into thin filaments to shorten the travel distance of the magnetic flux quantum 93, it is possible to reduce AC loss. This method is called multifilamentation. In the following description, the superconducting layer 92 divided into thin filaments is also called superconducting filament 92a or simply filament 92a.

[0009] A magnetic field H applied perpendicular to the superconducting layer 92 e (Strictly speaking, the component H of the applied magnetic field perpendicular to the superconducting layer 92 e 11(A) and (B), when the eddy current 99 varies with time, the eddy current 99 flows across the width of the superconducting layers 92 and 92a. Here, the eddy current 99 flows in a reciprocating direction as indicated by the reference symbols 99a and 99b, and the total width w e is called the width of the eddy current.

[0010] In the superconducting wires 90A(90) and 90B(90), the typical distance traveled by the magnetic flux quantum 93 is the width w e Therefore, the width of the eddy current w e If the width of the eddy current w is large, the AC loss is also large. e If the width can be narrowed, the AC loss can also be reduced.

[0011] Here, as shown in FIG. 11C, in a superconducting wire 90B (90) having a multifilamentary superconducting layer 92a for reducing AC loss, for some reason, some of the superconducting filaments 92a are locally expanded in width w f Consider a case where the entire superconducting wire 90B has transitioned from a superconducting state to a normal conducting state 95. If current 96 continues to flow through the filament 92a, a large amount of heat is generated due to the resistance of the normal conducting state. In this state, unless the current 96 can be diverted (i.e., diverted) from the filament 92a that has transitioned to the normal conducting state to the other filaments 92a that have maintained the superconducting state, the entire superconducting wire 90B will be quenched due to the large amount of heat generated in the filament that has transitioned to the normal conducting state. If the filament 92a is fThe probability of transitioning to the normal conducting state 95 throughout the filament 92a is f Multifilamentation reduces robustness against quenching because the narrower the filament 92a, the higher the AC losses will be. f The robustness decreases when the wire is narrowed. The high-temperature superconductor described in Patent Document 1 corresponds to this case.

[0012] In contrast, as shown in Fig. 12(A), if a conductor diversion layer, for example a copper diversion layer 97, is formed on the surface of the multifilament superconducting layer 92a, diversion is possible even if a normal conductive state 95 occurs locally, and it may be possible to prevent a decrease in robustness. However, as shown in Fig. 12(B), when a magnetic field H e When the current varies with time, a coupling current 98 flows through the copper diversion layer 97 due to electromagnetic induction. The coupling current 98 first flows in the longitudinal direction from the front side to the back side through the superconducting layer 92a located on the left side of the figure, and then flows in the transverse direction to the right through the copper diversion layer 97. The coupling current 98 then flows in the longitudinal direction from the back side to the front side through the superconducting layer 92a located on the right side of the figure, then flows in the transverse direction to the left through the copper diversion layer 97, and returns to the superconducting layer 92a located on the left side of the figure. The coupling current 98 flowing in this manner inhibits the intrusion of the magnetic flux quantum 93 from between the multifilamentary superconducting layers 92a as seen in FIG. 11(B). That is, as shown in FIG. 12(C), due to the influence of this coupling current 98, the magnetic flux quantum 93 intrudes from the end of the superconducting wire 90C as shown by the reference numeral 94, not from the transverse end of each superconducting filament 92a, and the travel distance of the magnetic flux quantum 93 is not shortened. Thus, if copper distribution layer 97 is formed in an attempt to prevent a decrease in robustness, the respective superconducting filaments 92a will be coupled via copper distribution layer 97, making it impossible to reduce AC loss.

[0013] Furthermore, when the entire superconducting wire 90C is quenched, the hot spot temperature rises due to Joule loss. In order to prevent the superconducting wire 90C from burning due to quenching, it is important to reduce the normal conduction resistance of the superconducting wire 90C. However, if the copper shunt layer 97 is formed thick in an attempt to reduce the normal conduction resistance and suppress the rise in the hot spot temperature, the attenuation of the coupling current 98 is hindered, hindering the reduction of AC loss.

[0014] In this way, reducing AC loss and improving robustness are essentially contradictory. Toward the practical application of high-temperature superconducting devices, it is necessary to achieve both reduction in AC loss and improvement in robustness in superconducting wires.

[0015] An object of the present invention is to provide a superconducting wire and a superconducting cable which achieve both reduced AC loss and improved robustness. [Means for solving the problem]

[0016] In order to achieve the above object, the present invention includes, for example, the following aspects. (Section 1) A plurality of superconducting layers extending in a longitudinal direction of a substrate and arranged in parallel in a lateral direction of the substrate; an insulating portion extending in the longitudinal direction of the substrate and disposed between the plurality of superconducting layers to electrically insulate the plurality of superconducting layers; a plurality of connection portions disposed on the insulating portion along the longitudinal direction of the substrate, the connection portions superconductively and electrically connecting the plurality of adjacent superconducting layers; Equipped with When wound in a spiral, the following conditions are met:

number

number

number

number

number

[0017] According to the present invention, it is possible to provide a superconducting wire and a superconducting cable which achieve both reduced AC loss and improved robustness. [Brief description of the drawings]

[0018] [Figure 1] 1 is a diagram illustrating a schematic configuration of a superconducting wire 10A according to a first embodiment of the present invention. [Diagram 2] 1 is a diagram illustrating a schematic configuration of a superconducting cable 20A formed using a superconducting wire 10A according to a first embodiment of the present invention. [Diagram 3] This is a plan view of the superconducting wire 10A according to the first embodiment of the present invention, cut out in a plane including the superconducting layer 2 and the joint 4, and shows an example in which the superconducting wire 10A does not satisfy the conditions for achieving both reduced AC loss and improved robustness. [Figure 4] This is a plan view of a superconducting wire 10A according to the first embodiment of the present invention, cut out in a plane including a superconducting layer 2 and a joint 4, and shows an example in which the superconducting wire 10A satisfies the conditions for achieving both reduced AC loss and improved robustness. [Diagram 5] FIG. 1 is a schematic side view of a superconducting cable 20A according to a first embodiment of the present invention, showing a state in which the superconducting wire 10A is spirally wound along the axis of the core material 9, thereby realizing the conditions for the superconducting wire 10A to achieve both reduced AC loss and improved robustness. [Figure 6] FIG. 10 is a diagram illustrating a schematic configuration of a superconducting wire 10B according to a second embodiment of the present invention. [Figure 7] This is a plan view of a superconducting wire 10B relating to the second embodiment of the present invention, cut out in a plane including a superconducting layer 2 and a joint 4, and shows an example in which the superconducting wire 10B satisfies the conditions for achieving both reduced AC loss and improved robustness. [Figure 8] 10 is a diagram illustrating a schematic configuration of a superconducting wire 10C according to a third embodiment of the present invention. FIG. [Figure 9] FIG. 2 is a diagram illustrating a configuration of a superconducting wire 10D according to a modified example of the first embodiment of the present invention. [Figure 10] FIG. 2 is a schematic diagram of a superconducting wire 80 for explaining the meaning of terms used in this specification. [Figure 11] FIG. 1 is a schematic diagram for explaining technical problems associated with a superconducting wire 90 according to the prior art. [Figure 12] FIG. 1 is a schematic diagram for explaining technical problems associated with a superconducting wire 90 according to the prior art. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the following description and drawings, the same reference numerals denote the same or similar components, and therefore, redundant description of the same or similar components will be omitted. [Terminology]

[0020] The meanings of terms used in the following description will be explained. Note that some terms have already been explained in the original text, but will be explained again for confirmation.

[0021] The electromotive force is a magnetic field H applied perpendicularly to the superconducting layer 81 of the superconducting wire 80 as shown by the dashed line in FIG. e (Strictly speaking, the component of the applied magnetic field perpendicular to the superconducting layer 81, H e) fluctuates over time, the force acts in a loop to cause an eddy current 82 to flow in the superconducting wire 80 by electromagnetic induction. The length L of the longest part of the loop of the electromotive force 83 along the longitudinal direction of the superconducting wire 80 is i (From now on, for the sake of simplicity, we will use the term "electromotive force loop length L i ") is the magnetic field H e are in the same direction, more precisely the magnetic field H e Time derivative of dH e The length of the superconducting wire 80 in the longitudinal direction where the θ and θ are in the same direction is equal to the length of the portion of the superconducting wire 80 in the longitudinal direction where the θ and θ are in the same direction. However, even if an electromotive force is generated, if there is no conductor or superconductor, no eddy current can flow. Unless otherwise specified, in this specification, electromotive forces are illustrated using dashed lines.

[0022] The eddy current 82 refers to a current induced in a loop (vortex) shape in a conductor or superconductor by an electromotive force 83 due to electromagnetic induction. The eddy current 82 is a concept that includes both persistent eddy currents and coupling currents, which will be described later. Unless otherwise specified, in this specification, eddy currents are illustrated using solid lines.

[0023] The length of the eddy current is the length of the longest part of the eddy current 82, which is shown by the solid line and distributed in the superconducting wire 80 as shown in FIG. 10, along the longitudinal direction of the superconducting wire 80. e The eddy current 82 is expressed as the length L of the electromotive force loop. i In other words, the eddy current can only flow within the length L e is the length of the electromotive force loop, L i It will never exceed.

[0024] The width of the eddy current is the length of the longest part of the eddy current 82, which is shown by the solid line and distributed in the superconducting wire 80, along the short side of the superconducting wire 80, as shown in FIG. 10, and is indicated by the symbol w e 11(A) and (B), the eddy current 82 flows in a reciprocating direction as indicated by the reference symbols 99a and 99b, and the typical distance traveled by a magnetic flux quantum 93 is the width w of the eddy current. e and hence the width of the eddy current w eIf the gap can be narrowed, AC losses can be reduced.

[0025] Persistent eddy currents refer to eddy currents that flow only in superconductors and that can be considered to be time-invariant (non-decaying) on ​​practical time scales (e.g., hours to years). Unless otherwise specified, persistent eddy currents are illustrated in this specification using solid lines.

[0026] The coupling current is a kind of eddy current. For example, referring to FIG. 12(B), the path of the coupling current 98 flowing through the superconducting wire 90C having the copper diversion layer 97 is as follows. The coupling current 98 first flows from the front side to the back side in the longitudinal direction through the superconducting layer 92a located on the left side of the figure, and then flows in the short direction to the right through the copper diversion layer 97. The coupling current 98 then flows from the back side to the front side in the longitudinal direction through the superconducting layer 92a located on the right side of the figure, and then flows in the short direction to the left through the copper diversion layer 97, and returns to the superconducting layer 92a located on the left side of the figure. The coupling current 98 decays over time because the copper diversion layer 97, which is a conductor, is included in the path. From another perspective, if the period of the magnetic field fluctuation is sufficiently long compared to the coupling time constant, which is the decay time constant of the coupling current, it can be considered that the coupling current hardly flows. Unless otherwise specified, the coupling current is illustrated using a dashed line in this specification. [First embodiment]

[0027] 1 is a diagram showing a schematic configuration of a superconducting wire 10A according to a first embodiment of the present invention. (A) is a perspective view of the superconducting wire, (B) is a plan view of the superconducting wire, and (C) is a cross-sectional view of the superconducting wire taken along line 1B-1B shown in (B). In the illustrated embodiment, the Y-axis direction is the longitudinal direction of the superconducting wire 10A, the X-axis direction is the transverse direction of the superconducting wire 10A, and the Z-axis direction is the thickness direction of the superconducting wire 10A.

[0028] The superconducting wire 10A (10) according to the first embodiment includes a substrate 1, a plurality of superconducting layers 2, an insulating portion 3, and a plurality of connection portions 4, and when wound in a spiral shape, satisfies the conditions for achieving both reduced AC loss and improved robustness, which will be described in detail below.

[0029] The substrate 1 is formed in a tape shape using, for example, a nickel-based alloy, stainless steel, or the like. For example, Hastelloy (registered trademark) can be used as the material of the substrate 1. The substrate 1 is flexible, and the superconducting wire 10A is wound in a spiral shape when used.

[0030] An intermediate layer (not shown) serving as a base for the superconducting layer 2 is formed on the surface of the substrate 1 as necessary. The material for the intermediate layer may be a material whose physical property values, such as thermal expansion coefficient and lattice constant, are intermediate between those of the substrate 1 and the superconductor constituting the superconducting layer 2. Illustratively, LaMnO3 may be used as the material for the intermediate layer. In this embodiment, an intermediate layer is formed on the surface of the substrate 1, and in the description in this specification, the substrate 1 having the intermediate layer formed on its surface is collectively referred to as the substrate 1.

[0031] The superconducting layer 2 superconductively passes a current in the superconducting wire 10A. In order to reduce AC loss, the superconducting layer 2 is multifilamented and formed on the surface of the substrate 1. The superconducting layer 2 extends in the longitudinal direction of the substrate 1, and a plurality of the superconducting layers 2 are arranged in parallel in the lateral direction of the substrate 1. Exemplarily, the superconducting layer 2 is formed using a REBCO high temperature superconductor, which is a ceramic. REBCO has the chemical formula REBa2Cu3O 7-δ (RE is a rare earth element such as Y, Gd, Eu, Sm, etc.) It is a copper oxide superconductor having a composition formula represented by the following. In the following description, the multifilamentary superconducting layer 2 will be referred to as a superconducting filament 2, or simply as a filament 2 or simply as a superconducting layer 2 for short.

[0032] The insulating portion 3 extends in the longitudinal direction of the substrate 1, is disposed between the multiple superconducting layers 2, 2, and electrically insulates the multiple superconducting layers 2, 2. Illustratively, in this embodiment, the insulating portion 3 is formed as a groove that exposes the surface of the substrate 1 by three-dimensionally patterning the superconducting layer 2 by, for example, a known photolithography process. In this embodiment, the superconducting wire 10A includes multiple insulating portions 3, and each insulating portion 3 is disposed between the multiple superconducting layers 2, 2 that are disposed in parallel.

[0033] The connection parts 4 are disposed in the insulating part 3 along the longitudinal direction of the substrate 1, and superconductively electrically connect adjacent superconducting layers 2, 2. The superconducting wire 10A is provided with a plurality of connection parts 4 in the insulating part 3 along the longitudinal direction of the substrate 1. In this embodiment, the connection parts 4 are formed integrally with the superconducting layer 2 using the same superconductor material as the superconducting layer 2.

[0034] The connection parts 4 electrically connect adjacent superconducting layers 2, 2 in a superconducting manner, thereby improving the superconducting shunting of the current flowing through the superconducting layers 2 and improving the robustness of the superconducting wire 10A. In other words, even if a transition to a normal conductive state occurs locally in a certain superconducting layer 2 for some reason, the connection parts 4 superconductingly bridge between adjacent superconducting layers 2, 2 and shunt the current from the superconducting layer 2 that has transitioned to a normal conductive state to the adjacent superconducting layer 2, preventing quenching of the entire superconducting wire 10A.

[0035] Exemplarily, the length (width) of the superconducting wire 10A along the short side is about 2 mm to about 4 mm, preferably about 1 mm to about 4 mm. The length (width) of one multifilamentary superconducting layer 2 along the short side is preferably about 0.4 mm to about 1 mm, more preferably about 0.1 mm to about 1 mm. Exemplarily, the thickness of the entire superconducting wire 10A including the substrate 1 and the superconducting layer 2 is within a range of about 150 μm to about 50 μm, preferably about 50 μm to about 30 μm. Since the superconducting wire 10A is used in a spirally wound state, more preferably, the thickness of the entire superconducting wire 10A including the substrate 1 and the superconducting layer 2 is less than about 30 μm.

[0036] In order to achieve both a reduction in AC loss and an improvement in robustness, when the superconducting wire 10A (10) is wound in a spiral shape, the following conditions are satisfied in order to reduce AC loss.

number

[0037] D is the diameter of the helix, P is the length of the helix pitch along the winding axis direction, and L is the length of the insulating portion 3 along the longitudinal direction. The helix diameter D and the helix pitch length P are as exemplified in Figures 2 and 5 described below. Illustratively, the helix diameter D is about 3 mm, the helix pitch length P is about 7.5 mm, and the length L of the insulating portion 3 along the longitudinal direction is about 10 mm.

[0038] Preferably, the superconducting wire 10A (10) satisfies the following condition in view of the need to reduce AC loss: g is the length of the joint 4 along the longitudinal direction, and n is a natural number equal to or greater than 1. Illustratively, the length g of the joint 4 along the longitudinal direction is about 2 mm.

number

[0039] Preferably, the superconducting wire 10A (10) satisfies the following condition in order to reduce AC loss: fis the length of the superconducting layer 2 along the short direction.

number

[0040] Preferably, the superconducting wire 10A (10) satisfies the following conditions in view of the need for improved robustness.

number

[0041] Preferably, the superconducting wire 10A (10) satisfies the following condition in order to improve robustness: t is the length of the superconducting wire 10A (10) along the short side direction.

number

[0042] The principle for achieving both reduced AC loss and improved robustness will be described later with reference to FIGS.

[0043] FIG. 2 is a diagram illustrating a schematic configuration of a superconducting cable 20A formed using a superconducting wire 10A according to the first embodiment of the present invention.

[0044] A superconducting cable 20A (20) according to the first embodiment includes a core material 9 and a superconducting wire 10A wound in a spiral shape around the axis of the core material 9.

[0045] In this embodiment, the core material 9 is a solid cylindrical member. For example, the core material 9 may be made of stainless steel or copper.

[0046] The superconducting wire 10A (10) is wound in a spiral shape, and the length of the loop of the electromotive force generated in the superconducting wire 10A (10) is L iThe length of the superconducting wire 10A can be shortened. In this embodiment, the superconducting wire 10A is wound around the outer wall of the core material 9 in the direction in which a left-handed screw advances, and the winding axis direction is the direction in which the left-handed screw advances. In the illustrated embodiment, a single layer of the superconducting wire 10A (10) is wound in a spiral shape along the axis of the core material 9. In the illustrated embodiment, three superconducting wires 10A (10A1, 10A2, 10A3) are wound in a trifiler shape in three parallel spiral shapes around the outer wall of the core material 9. Of the three superconducting wires 10A1, 10A2, 10A3 illustrated, the detailed structure of the superconducting wire 10A1 is illustrated, but the detailed structures of the superconducting wires 10A2, 10A3 are omitted from the illustration. [principle]

[0047] 3 and 4 are plan views of the superconducting wire 10A according to the first embodiment of the present invention, cut out in a plane including the superconducting layer 2 and the joints 4. FIG. 3 shows an example in which the superconducting wire 10A does not satisfy the conditions for achieving both reduced AC loss and improved robustness. FIG. 3(A) shows a case in which the length L of the insulating parts 3 is short, i.e., the interval between the joints 4 is short, and robustness can be improved, but the width w of the superconducting wire 10A is too small. t In this example, a wide persistent eddy current 11 flows across the width w of each superconducting filament 2, making it impossible to reduce AC loss. f In this example, the insulating portion 3 is confined within the wire and has a narrow width, so that the AC loss can be reduced, but the length L of the insulating portion 3 is long, i.e., the distance between the connecting portions 4 is long, so that the robustness cannot be improved. Fig. 4 shows an example in which the superconducting wire 10A satisfies the conditions for achieving both the reduction in AC loss and the improvement in robustness.

[0048] Fig. 5 is a schematic side view of a superconducting cable 20A according to a first embodiment of the present invention, showing a state in which the superconducting wire 10A is spirally wound around the axis of the core material 9, thereby realizing the conditions for the superconducting wire 10A to achieve both reduced AC loss and improved robustness. In Fig. 5, for the sake of simplicity of illustration and explanation, only one superconducting wire 10A is shown. In Fig. 5, reference numeral 11a denotes a persistent eddy current 11a occurring in a region of the superconducting wire 10A located on the front side of the core material 9 in a side view of the superconducting cable 20A, and reference numeral 11b denotes a persistent eddy current 11b occurring in a region of the superconducting wire 10A located on the back side of the core material 9. <Reducing AC losses>

[0049] Hereinafter, the principle of reducing AC loss while improving robustness will be described with reference to Figs. 3 to 5.

[0050] In order to achieve a reduction in AC loss by making the superconducting layer 2 multifilamentary, a wide (w e The insulating part 3 blocks the persistent eddy current 11 of the superconducting filament 2 having a width w f Narrow (w e On the other hand, as will be described later, in order to improve robustness, it is desirable that the interval between the connection parts 4, i.e., the length L of the insulating part 3, be short.

[0051] A magnetic field H applied perpendicularly to the superconducting layer 2 of the superconducting wire 10A e (Strictly speaking, the component of the applied magnetic field perpendicular to the superconducting layer 81, H e When the voltage V 1 varies with time, a loop-shaped electromotive force 19 that tries to cause an eddy current to flow in the superconducting wire 10A is induced by electromagnetic induction. The length L of the electromotive force loop is i is a magnetic field H applied perpendicularly to the superconducting layer 2 along the longitudinal direction of the superconducting wire 10A, regardless of the length L of the insulating portion 3. eHere, in order to improve robustness, the connection parts 4 are arranged at short intervals, that is, the length L of the insulating part 3 is short, and the length L of the insulating part 3 is equal to the length L of the electromotive force loop. i In this case, as shown by the solid line in Fig. 3(A), a wide persistent eddy current 11 continues to flow through the multiple superconducting filaments 2, 2 via the joint 4, and the effect of reducing AC loss by forming the superconducting layer 2 into a multifilament is not achieved.

[0052] In contrast, as shown in FIG. 3B, the length L of the insulating part 3 is equal to the length L of the electromotive force loop. i If the filament is longer than this, the insulating portion 3 will block the persistent eddy currents that are wide in the vertical direction in the figure across the multiple filament-shaped superconducting layers 2, 2, and the persistent eddy currents 11 will flow across the width w of each superconducting filament 2. f Narrow (w e This reduces AC losses.

[0053] Length of electromotive force loop L i is determined by the shape of the coil formed using superconducting wire or cable, but it often extends to the entire length (e.g., tens to hundreds of meters) or even several meters of the winding used to form the coil. Therefore, in order to block the wide, persistent eddy currents, it is necessary to use a long L i If the length L of the insulating portion 3 is made larger than the above, the interval between the connecting portions 4 will be too long and improvement in robustness cannot be expected.

[0054] In order to improve robustness by arranging the connection parts 4 at short intervals and then by using the insulation part 3 to block the wide persistent eddy currents and reduce AC losses, some measure must be taken to reduce the length L of the electromotive force loop as shown in Figure 4. i It is necessary to make the length of the insulating portion 3 shorter than the length L of the insulating portion 3, which has been shortened in order to improve robustness.

[0055] In the present invention, as shown in FIG. 5, the superconducting wire 10 is wound in a spiral shape around the axis of the core material 9, and as shown in FIG. 4, the length of the electromotive force loop is Li is made shorter than the length L of the insulating portion 3.

[0056] When the superconducting wire 10A (10) is wound in a spiral shape along the axis of the core material 9, the length P of the superconducting wire 10A, which corresponds to the length P of the spiral pitch, is t can be expressed as the following equation (1) using the diameter D of the spiral.

number

[0057] By winding the superconducting wire 10A (10) in a spiral shape along the axis of the core material 9, a magnetic field H applied perpendicularly to the superconducting layer 2 of the superconducting wire 10A (10) e (Strictly speaking, the component of the applied magnetic field perpendicular to the superconducting layer 2, H e ) is the length P of the helical pitch of the superconducting wire 10A given by Equation (1). t As a result, the length of the electromotive force loop determined by the magnetic field, L, is i Also, the length P of the helical pitch of the superconducting wire 10A t It is half the length, which is significantly shorter.

number

[0058] In this way, by winding the superconducting wire 10A in a spiral shape, the length of the electromotive force loop L i can be made shorter than the length L of the insulating portion 3, which is shortened to improve robustness, and thus the narrow width (w e In other words, the persistent eddy current 11 flowing in the superconducting wire 10A has a width w of each superconducting filament 2. f The width w of the persistent eddy current 11 (11a, 11b) is e At this time, the width w of each superconducting filament 2 becomes narrower. fThe state of the narrow persistent eddy currents 11 (11a, 11b) confined within is also illustrated in Figure 5. This allows for reduced AC losses while improving robustness.

[0059] That is, if the helical pitch length P and the helical diameter D satisfy the formula (3) with respect to the length L of the insulating portion 3, the AC loss can be reduced.

number

[0060] From the viewpoint of improving robustness, it is preferable that the length L of the insulating part 3 along the longitudinal direction is as short as possible while satisfying the condition of formula (3), because this increases the number of connecting parts 4 that function as bypass paths for the current.

[0061] Alternatively, as another exemplary upper limit of the length L of the insulating portion 3, the following formula (4) can be defined.

number

[0062] Furthermore, in relation to the condition of formula (3), it is possible to specify a condition under which, under the condition that the average transverse magnetic field to the helix is ​​constant, within one pitch of the helix, an electromotive force 19 that tries to cause a wide, persistent eddy current 11 to flow through the multiple superconducting filaments 2, 2 via the joint 4 is not induced at all. This formula (5) is a more preferable condition for reducing AC losses. In formula (5), g is the length of the joint 4 along the longitudinal direction, and n is a natural number equal to or greater than 1.

number

[0063] Equation (5) is an equation assuming that the loop of electromotive force 19 passes through the center of the connection part 4 in the longitudinal direction. The connection part 4 has a length g in the longitudinal direction. If the length P of the spiral pitch and the diameter D of the spiral satisfy the following equation (6) for a certain length L of the insulating part 3 along the longitudinal direction, the condition that the electromotive force 19 that tries to cause a wide persistent eddy current 11 to flow through the multiple superconducting filaments 2, 2 via the connection part 4 is not induced in the first place is satisfied. When the left side and the middle side of equation (6) are connected with an equal sign, the electromotive force 19 becomes zero for the loop that passes through the inner edge of the connection part 4, and when the middle side and the right side of equation (6) are connected with an equal sign, the electromotive force 19 becomes zero for the loop that passes through the outer edge of the connection part 4. In this way, taking into account the longitudinal length g of the connection part 4, the condition for reducing the AC loss shown in equation (5) can be specified as the condition shown in the following equation (6).

number

[0064] By shortening the length g of the connection 4, the current flowing through the connection 4 can be limited superconductively, and therefore the wide persistent eddy current can be limited. The length g of the connection 4 along the longitudinal direction is the length (width) w of the superconducting layer 2 along the transverse direction. f It is desirable that the following:

number

[0065] The condition of formula (7) can also be called the condition under which the persistent eddy current 11 just saturates or does not saturate the outermost superconducting layer 2. When this condition is satisfied, the superconducting wire 10A has a width of at least w t No persistent eddy current can flow through the joint 4 throughout the entire wire. Equation (7) is based on the idea that the width w f It should be noted that if a lower limit for the length g of the equation (7) is provisionally indicated, then 0≦g, and the lower limit for the length g is zero. <Principle of reducing error magnetic field>

[0066] The principle of reducing the error magnetic field will be described with reference to FIG. 11 and FIG.

[0067] As shown in FIG. 11A, in a superconducting wire 90A in which the superconducting layer 92 is not multifilamentary, a magnetic field H e When varies with time, Lenz's law determines that the magnetic field H e The eddy current 99 flows in a direction that hinders the fluctuation of the eddy current. The eddy current 99 flows in a distributed manner within the superconducting layer 92. That is, on the left side of the figure, a bundle of eddy currents 99a flows in the superconducting layer 92 in the longitudinal direction from the front side to the back side with a width w e On the right side of the figure, the flux of eddy current 99b flows in one direction with a width of w e / 2 flows in one direction.

[0068] Such eddy currents 99 (99a, 99b) flow as persistent eddy currents in the superconducting layer 92. On the other hand, persistent eddy currents are unexpected currents that are not taken into consideration when designing electromagnets and the like, and therefore cause error magnetic fields in electromagnets that are required to generate highly accurate magnetic fields, such as electromagnets for nuclear magnetic resonance (NMR) devices, electromagnets for nuclear magnetic resonance imaging (MRI), and electromagnets for particle beam accelerators.

[0069] In contrast, in the superconducting wire 10 of the present invention in which the superconducting layer 2 is multifilamentary and adjacent superconducting filaments 2, 2 are superconductively bridged by the connection portion 4, the error magnetic field is reduced while improving robustness, as described below.

[0070] As illustrated in FIG. 4, in the superconducting wire 10 according to the present invention in which the superconducting layer 2 is multifilamentary, the magnetic field H applied perpendicularly to the superconducting filaments 2 is also the same as in the superconducting wire 90A in which the superconducting layer 92 is not multifilamentary. e When the magnetic field fluctuates over time, persistent eddy currents 11 flow according to Lenz's law. At this time, the persistent eddy currents flow while being confined within each superconducting filament 2 (2a, 2b, 2c, 2d). When attention is paid to the direction of the persistent eddy currents 11 between adjacent superconducting filaments 2, 2, the directions of the persistent eddy currents 11 present in close positions on the adjacent sides are opposite to each other, and the magnetic fields they create cancel each other out.

[0071] For example, refer to the direction of the persistent eddy currents 11a that are close to each other between the adjacent filaments 2a and 2b. In the filament 2a, the persistent eddy currents 11a on the side adjacent to the filament 2b are oriented to the left in the figure, and in the filament 2b, the persistent eddy currents 11a on the side adjacent to the filament 2a are oriented to the right in the figure. In this way, between the multiple adjacent filaments 2a and 2b, the persistent eddy currents 11a that exist in close positions on the adjacent sides have opposite directions.

[0072] As for the direction of the adjacent persistent eddy currents 11a between the adjacent filaments 2b and 2c, similar to the case of the filaments 2a and 2b described above, the directions of the persistent eddy currents 11a existing in close positions on the adjacent sides are opposite to each other. The same is true for the filaments 2c and 2d. The persistent eddy current 11b is similar to the persistent eddy current 11a described above. As a result, in the example of Figure 4, there remain a magnetic field generated by the upper component of the loop of the persistent eddy current 11 in the filament 2a and a magnetic field generated by the lower component of the loop of the persistent eddy current 11 in the filament 2d.

[0073] In this way, in the superconducting wire 10 according to the present invention, the persistent eddy currents 11 present at positions close to each other between adjacent superconducting filaments 2, 2 have opposite directions, and the magnetic fields they generate cancel each other out. As a result, only the magnetic field generated by the outer components of the loops of the persistent eddy currents 11 flowing in the superconducting filaments 2a, 2d located on both sides (the uppermost and lowermost sides in the figure) at the outermost sides in terms of the width of the superconducting wire 10 remains. As a result, in the superconducting wire 10 according to the present invention in which the superconducting layer 2 is multifilamentary, the error magnetic field generated by the persistent eddy currents, which are currents unexpected in the design, is reduced. <Improved robustness>

[0074] In order to improve robustness, it is necessary to facilitate the division of current from one superconducting filament 2 to an adjacent superconducting filament 2. For this purpose, it is desirable that the length L of the insulating part 3 is short, that is, the interval between the connecting parts 4 is short, and the length g of the connecting parts 4 is long.

[0075] When a normal conduction occurs locally in a certain superconducting layer 2, the maximum value of the current that bypasses the normal conducting portion is half of the current that flows through the entire superconducting wire 10A (10). Therefore, as defined by the following formula (8), the length g of the connection 4 for dividing the current is calculated by multiplying the width w of the superconducting wire 10A (10) by the length g of the connection 4 for dividing the current by the width w of the superconducting wire 10A (10). tIf the width w of the superconducting wire 10A(10) is at least half of the width w of the superconducting wire 10A(10), the maximum possible current can be diverted at one connection 4. t 4. The lower limit of the length g of the connecting portion 4, which is determined by the relationship between

number

[0076] Furthermore, if the length g of the connection 4 along the longitudinal direction is too short, this length g becomes a bottleneck, and the current cannot smoothly bypass the normal conductive portion and flow from the adjacent superconducting layer 2. The condition for a current to bypass defects and normal conductive portions occurring inside one superconducting filament 2 via one connection 4 can be defined as shown in the following equation (9). From the viewpoint of improving robustness, equation (9) is defined as the width w f 4. The lower limit of the length g of the connecting portion 4, which is determined by the relationship between

number

[0077] Needless to say, it is preferable that the length g of the connection 4 is long in terms of dividing the current. However, in the connection 4, the superconducting layers 2, 2 are not divided by the insulating portion 3, and as a result, the width w e If an upper limit for the length g of the connection part 4 is to be specified from the viewpoint of improving robustness, the condition of the following formula (10), which is the limit at which the effect of reducing AC loss due to division is almost not observed, can be considered as an example.

number

[0078] In the superconducting wire 10 according to the present invention, the connection portion 4 is present between the superconducting layers 2, 2, and the adjacent superconducting layers 2, 2 that are divided are electrically connected in a superconducting manner. Therefore, even if a certain superconducting layer 2 has a defect or a normal conductive portion is locally generated in a certain superconducting layer 2 and the superconducting layer 2 cannot superconductively pass a current, the current can be superconductively diverted through the connection portion 4. Therefore, unlike the conventional superconducting wire 90B not having the connection portion 4 and in which the superconducting layer 2 is completely electrically divided, and the conventional superconducting wire 90C in which the superconducting layers 2, 2 are electrically connected in a normal conductive manner by the copper shunting layer 97, in the superconducting wire 10 according to the present invention having the connection portion 4, the division of the superconducting layer 2 by multifilamentation does not impair robustness. [effect]

[0079] As described above, the superconducting wire 10A and the superconducting cable 20A according to the first embodiment of the present invention can reduce AC loss and error magnetic field while improving robustness. The superconducting wire 10A according to the first embodiment includes a plurality of connection parts 4 that electrically connect adjacent superconducting layers 2, 2 in a superconducting manner, and when wound in a spiral shape, satisfies the conditions for reducing AC loss and improving robustness, which have been described with reference to Figs. 3 to 5.

[0080] In the superconducting wire 10A according to the first embodiment, the length L of the insulating portion 3 is shortened, so that the connecting portion 4 superconductively electrically connects adjacent superconducting layers 2, 2 at a sufficiently short interval. This improves the superconducting shunting of the current flowing through the superconducting layer 2, and improves the robustness of the superconducting wire 10A. In other words, even if a transition to a normal conducting state occurs locally in a certain superconducting layer 2 for some reason, the connecting portion 4 superconductively bridges between adjacent superconducting layers 2, 2, and shunts the current from the superconducting layer 2 that has transitioned to a normal conducting state to the adjacent superconducting layer 2, thereby preventing quenching of the entire superconducting wire 10A.

[0081] In addition, the superconducting wire 10A according to the first embodiment is wound in a spiral shape around the axis of the core material 9, so that the length L of the electromotive force loop is i is the length P of the superconducting wire 10A, which corresponds to the length P of the helical pitch. t and shorter than the length L of the insulating portion 3. This reduces AC loss and also reduces the error magnetic field. [Second embodiment]

[0082] A superconducting wire 10B (10) according to the second embodiment of the present invention differs from the superconducting wire 10A according to the first embodiment in that it further includes a conductive layer 5a (5) that covers the superconducting layer 2, the insulating portion 3, and the joint portion 4. The configuration of the superconducting wire 10B according to the second embodiment, which will be described below, is similar to that of the superconducting wire 10A according to the first embodiment unless otherwise specified, and therefore repeated description will be omitted.

[0083] 6 is a diagram showing a schematic configuration of a superconducting wire 10B according to a second embodiment of the present invention, in which (A) is a perspective view of the superconducting wire, (B) is a plan view of the superconducting wire, and (C) is a cross-sectional view of the superconducting wire taken along line 6B-6B shown in (B).

[0084] In the second embodiment, the superconducting wire 10B (10) further includes a conductive layer 5a (5) that covers the superconducting layer 2, the insulating portion 3, and the connecting portion 4. In the illustrated embodiment, the conductive layer 5a is formed to cover not only the superconducting layer 2, but also the superconducting layer 2, the insulating portion 3, and the connecting portion 4. The conductive layer 5a functions as a diversion layer that diverts the current flowing through the superconducting layer 2 when an abnormality occurs in the superconducting layer 2. Illustratively, the conductive layer 5a is made of copper. In the illustrated embodiment, the insulating portion 3 is formed as a groove whose bottom surface reaches the surface of the substrate 1, and the groove is filled with copper that functions as the conductive layer 5a.

[0085] Fig. 7 is a plan view of a superconducting wire 10B according to a second embodiment of the present invention, cut out in a plane including the superconducting layer 2 and the joint 4. Fig. 7 shows an example of a case in which the superconducting wire 10B satisfies the conditions for achieving both reduced AC loss and improved robustness.

[0086] The superconducting wire 10B according to the second embodiment includes the conductive layer 5a, and hence has improved robustness compared to the superconducting wire 10A according to the first embodiment.

[0087] According to the superconducting wire 10B of the second embodiment, it is possible to obtain the same AC loss reduction effect as the superconducting wire 10A of the first embodiment in a limited but practically sufficient operating frequency range.

[0088] Unlike the superconducting wire 10A according to the first embodiment, in the superconducting wire 10B according to the second embodiment, as shown by the dashed line in Fig. 7, a wide coupling current 12 flows across multiple superconducting layers 2, 2 (2a, 2b, 2c, 2d) in the vertical direction in the figure via the superconducting layer 2, the insulating portion 3, and the conductive layer 5a provided on the upper portion of the joint portion 4. Unless this coupling current 12 attenuates, the effect of making the superconducting layer 2 multifilamentary is not exhibited and the AC loss remains large.

[0089] With reference to Fig. 7, the behavior of the coupling current generated in the superconducting wire 10B and the behavior of the persistent eddy current after the coupling current decays will be described in detail. In the superconducting wire 10B in the state shown in Fig. 7, the coupling current 12 flows across the conductive layer 5b provided on the upper part of the insulating part 3, and the width of the eddy current for the coupling current 12 is wide in the vertical direction in the figure across multiple superconducting layers 2 (2a, 2b, 2c, 2d), and AC loss is large when the coupling current 12 is not decaying. If the period of the fluctuation of the applied magnetic field is the coupling time constant τ c If the width w of the eddy current 12 is sufficiently long compared to the width w of the eddy current 11, the coupling current 12 will decay and the persistent eddy current 11 confined in each superconducting filament 2 will flow.e is narrow and AC losses are small.

[0090] The coupling current is determined by the self-inductance L cc and resistor R cc The binding time constant τ is the ratio of c It decays with self-inductance L cc is the length of the eddy current (coupled current), L e is proportional to the resistance R cc is the length of the eddy current (coupled current), L e Therefore, the binding time constant τ c is the length of the eddy current (coupled current), L e Therefore, the length L of the eddy current (combined current) e If the length is long, the conductive layer 5a will impair the effect of reducing AC loss achieved by making the superconducting layer 2 multifilamentary.

[0091] In the second embodiment of the present invention, when the superconducting wire 10B is wound in a spiral shape like the superconducting cable 20A according to the first embodiment, the length L of the eddy current for the coupling current 12 is e This allows the coupling time constant τ c can be shortened.

[0092] The period of the magnetic field fluctuation is the reciprocal of the operating frequency. In the second embodiment, the operating frequency is the characteristic frequency f c =1 / (2πτ c ), AC losses are reduced and the error magnetic field is small.

[0093] In the second embodiment, when viewed from the side of the superconducting cable, persistent eddy current 11a is generated in a region of superconducting wire 10B located on the front side of core material 9, and persistent eddy current 11b is generated in a region of superconducting wire 10B located on the back side of core material 9, which is the same as in the first embodiment described with reference to Figures 4 and 5.

[0094] As in the first embodiment, the superconducting wire 10B according to the second embodiment can be wound in a spiral shape around the axis of the core material 9 to form a superconducting cable. <Considerations regarding the operating frequency at which AC loss reduction effects are realized>

[0095] When the conventional superconducting wire 90C shown in FIG. 12 is wound in a spiral shape, the decay time constant (coupling time constant) τ of the coupling current 98, which is an eddy current flowing between the multiple superconducting layers 92a, 92a through the copper shunting layer 97, c1 It has been experimentally confirmed that the temperature is given by the following equation (11) (at 77K):

number

[0096] where t Cu is the thickness of the copper plating copper shunt layer 97 which provides electrical conductivity between the multifilamentary superconducting layers 92a, 92a.

[0097] When the superconducting wire 10B according to the second embodiment of the present invention is wound in a spiral shape, if one side of the loop of the coupling current 12 passes through the joint 4, the resistance of the loop of the coupling current 12 is halved, and as shown in the following equation (12), the coupling time constant τ c2 is twice that of equation (11).

number

[0098] The binding time constant is τ c When c =1 / (2πτ c ) and the operating frequency is the characteristic frequency f c If the operating frequency is about one tenth of the value of the following formula (13), the coupling current attenuates, the AC loss is reduced, and the error magnetic field can be reduced. That is, in the superconducting wire 10B according to the second embodiment of the present invention provided with the joint 4, if the operating frequency is equal to or lower than the value of the following formula (13), the effect of reducing the AC loss and the effect of reducing the error magnetic field due to the persistent eddy current are exerted.

number

[0099] The frequency calculated by formula (13) is illustratively 500 Hz or more, which is higher than the operating frequencies of many electrical devices that operate on AC. In other words, the operating frequencies of many electrical devices are equal to or lower than the value of formula (13), and satisfy the operating frequency conditions for a state in which the superconducting wire 10 of the present invention exerts its AC loss reduction effect and its error magnetic field reduction effect. Therefore, the superconducting wire 10 and superconducting cable 20 of the present invention can be applied to electrical devices that operate on AC with improved robustness and with the AC loss reduction effect and error magnetic field reduction effect exerted. [Third embodiment]

[0100] A superconducting wire 10C (10) according to the third embodiment of the present invention is different from the superconducting wire 10A according to the first embodiment in that it further includes a conductive layer 5b (5) covering the superconducting layer 2. The configuration of the superconducting wire 10C according to the third embodiment described below is similar to that of the superconducting wire 10A according to the first embodiment unless otherwise specified, and therefore repeated description will be omitted.

[0101] 8 is a diagram showing a schematic configuration of a superconducting wire 10C according to a third embodiment of the present invention, in which (A) is a perspective view of the superconducting wire, (B) is a plan view of the superconducting wire, and (C) is a cross-sectional view of the superconducting wire taken along line 8B-8B shown in (B).

[0102] In the third embodiment, the superconducting wire 10C (10) further includes a conductive layer 5b (5) that covers the superconducting layer 2. In the illustrated embodiment, the conductive layer 5b does not cover the insulating portion 3 and the connecting portion 4, but is formed to cover only the superconducting layer 2. The conductive layer 5b functions as a diversion layer that diverts the current flowing through the superconducting layer 2 when an abnormality occurs in the superconducting layer 2. Illustratively, the conductive layer 5b is made of copper. Note that in the illustrated embodiment, the insulating portion 3 is formed as a groove that exposes the surface of the substrate 1, but the conductive layer 5b is formed to cover only the superconducting layer 2, and the groove is not filled with copper that functions as the conductive layer 5b.

[0103] In the third embodiment, in a side view of the superconducting cable, persistent eddy current 11a is generated in a region of superconducting wire 10C located on the front side of core material 9, and persistent eddy current 11b is generated in a region of superconducting wire 10B located on the back side of core material 9, which is similar to the first embodiment described with reference to Figures 4 and 5. With superconducting wire 10C according to the third embodiment, it is possible to obtain the same AC loss reduction effect as with superconducting wire 10A according to the first embodiment.

[0104] The superconducting wire 10C according to the third embodiment includes the conductive layer 5b, and thus has improved robustness compared to the superconducting wire 10A according to the first embodiment. More specifically, current is diverted from the superconducting layer 2 to the conductive layer 5b provided on the upper portion of the superconducting layer 2, thereby making it possible to suppress an increase in the hot spot temperature.

[0105] As in the first embodiment, the superconducting wire 10C according to the third embodiment can be wound in a spiral shape around the axis of the core material 9 to form a superconducting cable. [Other formats]

[0106] Although the present invention has been described above with reference to specific embodiments, the present invention is not limited to the above-described embodiments.

[0107] In the above embodiment, the superconducting wire 10 includes four multifilament superconducting layers 2, but the number of superconducting layers 2 is not limited. The superconducting wire 10 only needs to have at least one insulating portion 3 disposed between the multiple superconducting layers 2, 2, and the superconducting wire 10 only needs to have at least two superconducting layers 2. Similarly, in the above embodiment shown in the figures, the superconducting wire 10 includes three insulating portions 3, but the number of insulating portions 3 is not limited, and the superconducting wire 10 only needs to have at least one insulating portion 3.

[0108] In the above embodiment, the superconducting layer 2 is formed using a REBCO high-temperature superconductor, but the material of the superconducting layer 2 is not limited. 7-y A yttrium-based high-temperature superconductor represented by (y is the oxygen nonstoichiometry) or a bismuth-based high-temperature superconductor can be used for the superconducting layer 2. The superconductor used for the superconducting layer 2 is not limited to a high-temperature superconductor whose transition temperature exceeds the liquid nitrogen temperature (77 K), but a superconductor whose transition temperature is lower than the liquid nitrogen temperature can be used, and in the future, a superconductor whose transition temperature is closer to room temperature (approximately 300 K) can also be used. In other words, a superconductor that exhibits the superconducting phenomenon can be used for the superconducting layer 2.

[0109] In the above embodiment, the insulating part 3 is exemplarily formed as a groove that exposes the surface of the substrate 1, but the insulating part 3 is not limited to a groove. The insulating part 3 can be formed as a substantial member that is formed, for example, using various insulating materials. The insulating part 3 is disposed between the multiple superconducting layers 2, 2, and can electrically insulate the superconducting layers 2, 2, that is, can divide the conductivity. The insulating part 3 can also be expressed as a conductive dividing part that divides the superconducting conductivity of the multiple superconducting layers 2, 2. In addition, the insulating part 3 formed as a groove can electrically insulate the multiple superconducting layers 2, 2, and when an intermediate layer (not shown) is formed on the surface of the substrate 1, the insulating part 3 can be a groove that exposes the intermediate layer.

[0110] In the above-described embodiment, the connection portion 4 is formed integrally with the superconducting layer 2, but the connection portion 4 may be formed as a separate member from the superconducting layer 2. In the above-described embodiment, the connection portion 4 is formed using the same superconductor as the superconducting layer 2, but the superconductor used for the connection portion 4 may be different from the superconductor used for the superconducting layer 2. That is, the connection portion 4 only needs to be able to electrically connect adjacent superconducting layers 2, 2 in a superconducting manner. In the above-described embodiment, the connection portion 4 is arranged in alignment in the short-side direction across the multiple insulating portions 3 arranged in parallel, but as illustrated in FIG. 9, the connection portion 4 can also be arranged at a position away from a line along the short-side direction across the multiple insulating portions 3 arranged in parallel.

[0111] In the above embodiment, the conductive layer 5 (5a, 5b) is made of copper, but the material of the conductive layer 5 is not limited to copper. The conductive layer 5 can be made of a material having high electrical conductivity, such as silver or gold, that is used for electrical wiring, other than copper as exemplified.

[0112] In the above embodiment, the core material 9 is a solid member, but the core material 9 can also be a hollow member. For example, when the core material 9 is a solid member, the superconducting wire 10 can be wound in a spiral shape around the outer wall of the core material 9. For example, when the core material 9 is a hollow member, the superconducting wire 10 can be wound in a spiral shape around the outer wall of the core material 9, or can be wound in a spiral shape along the inner wall of the core material 9. That is, the core material 9 only needs to be able to wind the superconducting wire 10 in a spiral shape along the axis of the core material 9. The core material 9 can also be made of a stranded wire in which a plurality of strands are twisted together. The strands may or may not be insulated from each other. For the strands, for example, a metal wire such as copper or stainless steel can be used. For example, the cross-sectional shape of the core material 9 or the strands can be a honeycomb shape in which copper is partitioned by a high resistance material such as a copper-nickel alloy.

[0113] In the above embodiment, the core material 9 is a cylindrical member, but the cross-sectional shape of the member used for the core material 9 is not limited to a circle. The cross-sectional shape of the member used for the core material 9 may be, for example, an ellipse, a regular polygon such as a regular hexagon or an equilateral triangle, a rectangle, a regular polygon with rounded corners, or a rectangle with rounded corners. For example, in the case of a regular polygon, the cross-sectional shape of the member can be more closely approximated to a circle by increasing the number of corners of the regular polygon that represents the cross-sectional shape of the member.

[0114] In the above embodiment, the superconducting wire 10 is wound in a left-handed direction along the axis of the core material 9, but the superconducting wire 10 may be wound in a right-handed direction.

[0115] In the above embodiment, one layer of the superconducting wire 10 is wound in a spiral shape along the axis of the core material 9, but the number of layers of the superconducting wire 10 wound in a spiral shape along the axis of the core material 9 is not limited. By increasing the number of layers of the superconducting wire 10 and increasing the number of superconducting wires 10 used to manufacture a cable, a superconducting cable with an increased current capacity can be manufactured. For example, a superconducting cable with an increased current capacity can be manufactured by arranging n superconducting wires 10 in parallel on the same layer (for example, trifilar winding when n=3), winding them in a spiral shape along the axis of the core material 9, and stacking multiple such layers. Also, for example, a superconducting cable with an increased current capacity can be manufactured by stacking multiple superconducting wires 10 in multiple layers and then winding them in a spiral shape along the axis of the core material 9. In this way, when winding a plurality of superconducting wires 10 in a spiral shape along the axis of the core material 9, it is possible to combine stacking multiple layers in which a plurality of superconducting wires 10 are arranged in parallel on the same layer, with stacking and winding a plurality of superconducting wires 10 in multiple layers. [Explanation of symbols]

[0116] 1 Board 2(2a,2b,2c,2d,) superconducting layer 3 Insulation 4 Connection 5(5a,5b) Conductive layer 9 Core material 10(10A,10B,10C,10D) Superconducting wire 11(11a,11b) Persistent eddy currents 12 Combined current 19 Electromotive force 20(20A) Superconducting cable 80 Superconducting wire 81 Superconducting layer 82 Eddy current 83 Electromotive force 90(90A, 90B, 90C) Conventional superconducting wire 91 Substrate 92 Superconducting layer 92a Multifilamentary superconducting layer 93 Flux Quantum 95 Normal state 96 Current 97 Copper distribution layer 98 Combined current 99(99a,99b) Eddy current

Claims

1. A plurality of superconducting layers extending in a longitudinal direction of a substrate and arranged in parallel in a lateral direction of the substrate; an insulating portion extending in the longitudinal direction of the substrate and disposed between the plurality of superconducting layers to electrically insulate the plurality of superconducting layers; a plurality of connection portions disposed on the insulating portion along the longitudinal direction of the substrate, the connection portions superconductively and electrically connecting the plurality of adjacent superconducting layers; Equipped with the substrate is continuous along the short-side direction in a portion where the insulating portion is provided, When wound in a spiral, the following conditions are met: [0010] where D is a diameter of the helix, P is a length of the helix pitch along the winding axis direction, and L is a length of the insulation along the longitudinal direction.

2. 2. The superconducting wire according to claim 1, which satisfies the following conditions: [0025] Here, g is the length of the connection portion along the longitudinal direction, and n is a natural number of 1 or more.

3. 3. The superconducting wire according to claim 1 or 2, which satisfies the following conditions: [0030] where g is the length of the connection portion along the longitudinal direction, and w ｆ is the length of the superconducting layer along the short direction.

4. 4. The superconducting wire according to claim 3, which satisfies the following conditions: [0045] Here, w ｔ is the length of the superconducting wire along the short direction.

5. 3. The superconducting wire according to claim 1 or 2, which satisfies the following conditions: [0050] where g is the length of the connection portion along the longitudinal direction, and w ｆ is the length of the superconducting layer along the short direction.

6. 6. The superconducting wire according to claim 1, comprising a plurality of insulating portions, each of which is disposed between the plurality of superconducting layers that are disposed in parallel.

7. 7. The superconducting wire according to claim 6, wherein the plurality of connecting portions are arranged at positions spaced apart from a line along the short direction across the plurality of insulating portions arranged in parallel.

8. The superconducting wire according to claim 1 , wherein the insulating portion is a groove exposing the substrate.

9. The superconducting wire according to claim 1 , further comprising a conductive layer covering the superconducting layer.

10. The superconducting wire according to claim 9 , wherein the conductive layer further covers the insulating portion and the connection portion.

11. A core material; The superconducting wire according to any one of claims 1 to 10, which is wound in a spiral shape along an axis of the core material; A superconducting cable comprising:

Images