Superconducting conductors and windings

Abstract

To provide a superconducting conductor with reduced loss.SOLUTION: A superconducting conductor 10 comprises: a stranded wire 1 having multiple intertwined metal strands 11; and a tape-shaped superconducting wire material 2 having a superconducting layer formed on a surface of a flexible substrate and spirally wound around the stranded wire 1 along a longitudinal direction thereof. The metal strands 11 have a diameter of 0.3 mm or less, and the stranded wire 1 has a diameter of 5 mm or less.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a cable-shaped superconducting conductor and a winding formed by winding the superconducting conductor.

Background Art

[0002] As a technology for efficiently generating, transmitting, converting, using, and storing electrical energy, high-temperature superconductivity has attracted attention. For example, by using a wire made of a high-temperature superconducting material (hereinafter referred to as a high-temperature superconducting wire) or a superconducting conductor formed by aggregating such wires for the armature winding of a generator or an electric motor (motor), it becomes possible to pass a large current with a high current density through the armature winding. As a result, it becomes possible to reduce the armature core, and it is expected to reduce the weight of the generator and the electric motor. If it becomes possible to reduce the weight of the generator and the electric motor, for example, it leads to the realization of electrification of aircraft and the promotion of the introduction of large floating offshore wind power generation. When the electrification of aircraft is realized or the introduction of wind power generation is promoted, since a reduction in CO2 emissions is expected, high-temperature superconducting technology is expected to greatly contribute to the realization of a decarbonized society.

[0003] On the other hand, when a superconducting wire is used with alternating current, an alternating current loss occurs due to the alternating magnetic field. Generally, when a current flows through a superconducting wire or a magnetic field is applied, magnetic flux penetrates into the superconducting wire in the form of magnetic flux quanta. Under operating conditions where a direct current or a direct 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 magnetic field is applied, the distribution of magnetic flux changes at the position of the superconducting wire, so that the magnetic flux quanta must move. When the magnetic flux quanta move, something like friction occurs, and what corresponds to this frictional heat is the alternating current loss. In particular, in the alternating current application of a winding (coil), the alternating current loss due to an alternating magnetic field applied from the lateral direction (in the case where the superconducting wire or the superconducting conductor extends in the longitudinal direction, the direction intersecting the longitudinal direction) with respect to the superconducting wire or the superconducting conductor used for the winding becomes large.

[0004] Various methods have been proposed to reduce such AC losses that occur in superconducting wires. For example, Patent Document 1 discloses a superconducting conductor that reduces AC losses and a superconducting cable equipped with a superconducting conductor. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2008-47519 [Overview of the project] [Problems that the invention aims to solve]

[0006] A single superconducting wire can usually only carry a current of tens to hundreds of amperes. To implement high-temperature superconductivity in technology, there is a need to combine multiple superconducting wires into a highly flexible superconducting conductor capable of carrying large currents at high current densities and enabling winding.

[0007] However, most practical high-temperature superconducting wires are in tape form (hereinafter also referred to as superconducting tape wires), and it is not easy to combine multiple superconducting tape wires to construct a superconducting conductor that can carry large currents at high current density and has excellent flexibility. Simply stacking multiple superconducting tape wires results in an imbalance in inductance between the multiple superconducting tape wires, which leads to an uneven current distribution when AC current is applied. This reduces the amount of current that can flow in the superconducting state throughout the superconducting conductor, or increases AC losses, making it impossible to use the superconducting conductor for AC applications.

[0008] Furthermore, depending on the configuration of the superconducting conductor, it may include components other than the superconducting wire, such as a metal core material. When such a superconducting conductor is used with alternating current, eddy current losses occur in the core material, which is a metal component, due to the alternating magnetic field.

[0009] The fact that AC losses occur in superconducting wires, eddy current losses occur in metal components, and it is difficult to combine multiple superconducting tape wires to create a superconducting conductor that can carry large currents at high current densities and has excellent flexibility, are bottlenecks to the social implementation of devices using high-temperature superconductivity.

[0010] The present invention aims to provide a superconducting conductor with reduced losses.

[0011] Another object of the present invention is to provide a superconducting conductor in which the decrease in critical current is reduced or prevented. [Means for solving the problem]

[0012] The present invention, which solves the above problems, includes, for example, the following embodiments. (Section 1) A stranded wire having multiple metal strands twisted together, A tape-shaped superconducting wire having a superconducting layer formed on the surface of a flexible substrate, and being spirally wound around the stranded wire along its longitudinal direction, Equipped with, A superconducting conductor in which the diameter of the metal strand is 0.3 mm or less, and the diameter of the strand is 5 mm or less. (Section 2) The superconducting conductor according to item 1, wherein the angle between the longitudinal direction of the superconducting wire and the longitudinal direction of the stranded wire is 45 degrees or more and less than 90 degrees. (Section 3) The superconducting conductor according to item 1 or 2, wherein the plurality of metal strands are twisted together in the same direction. (Section 4) The superconducting conductor according to any one of items 1 to 3, wherein the plurality of metal strands are twisted together with the same twist pitch. (Section 5) The superconducting conductor according to any one of claims 1 to 4, further comprising a flexible smoothing layer disposed between the stranded wire and the superconducting wire so as to cover the periphery of the stranded wire along its longitudinal direction. (Item 6) The superconductor according to item 5, wherein the smoothing layer is formed using a resin or a metal and covers the periphery of the twisted wire in a cylindrical or spiral shape. (Item 7) Comprising a plurality of said superconducting wire materials, The superconductor according to any one of items 1 to 6, wherein the plurality of superconducting wire materials are wound spirally along the longitudinal direction around the twisted wire. (Item 8) The superconductor according to item 7, wherein the plurality of superconducting wire materials are wound spirally along the longitudinal direction around the twisted wire in different directions. (Item 9) In the superconducting wire material, The superconductor according to any one of items 1 to 8, wherein the plurality of superconducting layers extend in the longitudinal direction of the substrate and are arranged in parallel in the short-side direction of the substrate. (Item 10) The superconductor according to any one of items 1 to 9, further comprising a normal-conducting member that electrically connects the superconducting wire material and at least one of the metal strands included in the twisted wire. (Item 11) The superconductor further comprises a normal-conducting member that electrically connects the superconducting wire material and at least one of the metal strands included in the twisted wire, The superconductor according to any one of items 1 to 10, wherein the plurality of normal-conducting members are arranged so as to minimize the integral value of the lateral magnetic field with respect to the superconductor in the section of the superconductor between adjacent normal-conducting members. (Item 12) A twisted wire having a plurality of metal strands twisted together, A tape-shaped superconducting wire material having a superconducting layer formed on the surface of a flexible substrate and wound spirally along the longitudinal direction around the twisted wire, A flexible smoothing layer disposed between the twisted wire and the superconducting wire material so as to cover the periphery of the twisted wire along the longitudinal direction, A superconductor comprising: (Item 13) A stranded wire having a plurality of metal strands twisted together, A tape-shaped superconducting wire having a superconducting layer formed on the surface of a flexible substrate and wound spirally along the longitudinal direction around the stranded wire, Comprising: A superconducting conductor in which the bending angle of the superconducting wire along the outer periphery of the stranded wire is 12 degrees or less. (Item 14) A winding formed by winding the superconducting conductor according to any one of Items 1 to 13.

Advantages of the Invention

[0013] According to the present invention, a superconducting conductor with reduced losses can be provided.

Brief Description of the Drawings

[0014] [Figure 1] It is a schematic diagram for explaining the principle of reducing losses in the cable-shaped superconducting conductor according to the present invention. [Figure 2] It is a diagram schematically showing the configuration of a superconducting conductor 10A according to the first embodiment of the present invention. [Figure 3] It is a diagram showing the configurations of superconducting tape wires 2 in various aspects included in the superconducting conductor 10A according to the first embodiment of the present invention, and is a perspective view schematically showing the configuration of the superconducting wire 2A in the first aspect. [Figure 4] It is a diagram showing the configurations of superconducting tape wires 2 in various aspects included in the superconducting conductor 10A according to the first embodiment of the present invention, and is a perspective view schematically showing the configuration of the superconducting wire 2B in the second aspect. [Figure 5] It is a diagram showing the configurations of superconducting tape wires 2 in various aspects included in the superconducting conductor 10A according to the first embodiment of the present invention, and is a perspective view schematically showing the configuration of the superconducting wire 2C in the third aspect. [Figure 6] It is a diagram schematically showing the configuration of a superconducting conductor 10B according to the second embodiment of the present invention. [Figure 7]This is a schematic perspective view showing the configurations of various types of superconducting tape wires 2 (2D, 2E, 2F). [Figure 8] This graph shows the results of verifying the loss reduction effect in Example 1. [Figure 9] This figure schematically shows the structure of the superconducting conductor 10C(10) fabricated in Example 2. [Figure 10] These are the measurement results of the electric field-current characteristics of the superconducting conductor 10C(10) fabricated in Example 2. [Figure 11] This figure schematically shows the structure of the superconducting conductor 10D(10) fabricated in Example 3. [Figure 12] These are the measurement results of the electric field-current characteristics of the superconducting conductor 10D(10) fabricated in Example 3. [Figure 13] This figure schematically shows the structure of the superconducting conductor 10E(10) fabricated in Example 4. [Figure 14] These are the measurement results of the electric field-current characteristics of the superconducting conductor 10E(10) fabricated in Example 4. [Figure 15] This figure schematically shows the structure of the superconducting conductor 10F(10) fabricated in Example 5. [Figure 16] These are the measurement results of the electric field-current characteristics of the superconducting conductor 10F(10) fabricated in Example 5. [Figure 17] This figure schematically shows the structure of the superconducting conductor 10G(10) fabricated in Example 6. [Figure 18] These are the measurement results of the electric field-current characteristics of the superconducting conductor 10G(10) fabricated in Example 6. [Figure 19] This diagram schematically shows the structure of the superconducting conductor 90 fabricated as Comparative Example 3. [Figure 20] These are the measurement results of the electric field-current characteristics of the superconducting conductor 90 fabricated in Comparative Example 3. [Modes for carrying out the invention]

[0015] Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the following description and drawings, the same reference numerals indicate the same or similar components, and therefore, redundant explanations of the same or similar components will be omitted.

[0016] [Meaning of terms] The following explanation will define the terms used in this description. Some terms have already been explained in their initial appearance, but will be explained again for clarity.

[0017] A superconducting wire refers to a wire made using a superconducting material, and a superconducting tape wire refers to a flat, tape-shaped superconducting wire. Exemplary superconducting tape wires are shown in Figures 3 to 5. A superconducting conductor refers to a conductor made by assembling superconducting wires. Exemplary superconducting conductors assembled into a cable are shown in Figures 2 and 6.

[0018] AC losses are losses that occur when using a superconducting wire with alternating current, due to the alternating magnetic field. Generally, when an electric current flows through a superconducting wire or a magnetic field is applied, magnetic flux penetrates the wire in the form of magnetic flux quanta. Under operating conditions where a DC current or DC magnetic field is applied, the magnetic flux quanta remain stationary. However, under operating conditions where an AC current or AC magnetic field is applied, the distribution of magnetic flux changes at the position of the superconducting wire, forcing the magnetic flux quanta to move. When the magnetic flux quanta move, something akin to friction occurs, and the heat generated by this friction is equivalent to AC losses.

[0019] Electromotive force (EMF) is a "force" that acts in a loop-like manner to induce eddy currents within a superconducting wire when a magnetic field applied perpendicular to the superconducting layer of the superconducting wire (more precisely, the component of the applied magnetic field perpendicular to the superconducting layer) fluctuates over time. The longest part of the EMF loop along the longitudinal direction of the superconducting wire (hereinafter referred to as the "EMF loop length" for simplicity) is equal to the length of the longitudinal portion of the superconducting wire where the magnetic field is in the same direction, or more precisely, where the time derivative of the magnetic field is in the same direction. Note that even if EMF is generated, eddy currents cannot flow if there is no conductor or superconductor present.

[0020] Eddy currents are electric currents induced in a loop-like (vortex-like) pattern within a conductor or superconductor due to an electromotive force caused by electromagnetic induction. The concept of eddy currents includes both sustained eddy currents98 and coupled currents99.

[0021] The length of an eddy current is the longest length of an eddy current distributed and flowing through a superconducting wire, along the longitudinal direction of the wire. Eddy currents can only flow within the length of the electromotive force loop. In other words, the length of an eddy current cannot exceed the length of the electromotive force loop.

[0022] A coupled current is a type of eddy current, and the coupled time constant is the decay time constant of the coupled current. The coupled current is determined by the self-inductance L along its path. cc and resistor R cc The coupling time constant τ is the ratio of to c It is attenuated by the self-inductance L. cc It is proportional to the length of the eddy current (coupled current), and the resistance R cc The coupling time constant τ is inversely proportional to the length of the eddy current (coupling current). Therefore, the coupling time constant τ c It is proportional to the square of the length of the eddy current (coupled current).

[0023] [Principles of Loss Reduction] We envision fabricating a cable-like superconducting conductor by spirally winding a tape-shaped superconducting wire (superconducting tape wire) around a core material along its longitudinal direction. The losses in such a cable-like superconducting conductor consist of eddy current losses in the core material and AC losses in the superconducting tape wire.

[0024] In the cable-shaped superconducting conductor according to the present invention, by providing the configuration described below individually or in combination with other configurations, it is possible to reduce eddy current losses in the core material and AC losses in the superconducting tape wire.

[0025] Figure 1 is a schematic diagram illustrating the principle by which losses are reduced in the cable-shaped superconducting conductor according to the present invention.

[0026] In the cable-shaped superconducting conductor 10 according to the present invention, a tape-shaped superconducting wire 2 is spirally wound around a stranded wire 1 that functions as a core material. In Figure 1, (A) illustrates the case where the diameter of the stranded wire 1 is large and the winding angle θ of the tape-shaped superconducting wire 2 is small, and (B) illustrates the case where the diameter of the stranded wire 1 is small and the winding angle θ of the tape-shaped superconducting wire 2 is large. For ease of understanding, the superconducting wires 2 (2A, 2B, 2C) shown in the figure have the superconducting layer 22 wound around the stranded wire 1 with the superconducting layer 22 facing outwards, but the loss is similarly reduced even if the superconducting layer 22 is wound around the stranded wire 1 with the superconducting layer 22 facing inwards.

[0027] <Reduction of eddy current loss in core material> In the superconducting tape wire 2, when the superconducting state is destroyed, or when an overcurrent exceeding the current that can flow in the superconducting state flows through the superconducting tape wire 2 due to some external accident, for example, it is desirable that the core material be formed using a metal with high electrical conductivity (low electrical resistivity), such as copper, so that it can act as a bypass (diversion channel) for the current.

[0028] A cable-like superconducting conductor 10 is fabricated by using a solid single wire with a circular cross-section, a stranded wire made by twisting together relatively thick strands, or a stranded wire made by twisting together multiple strands that are not insulated from each other, as the core material, and then spirally winding a superconducting tape wire 2 around the core material along its longitudinal direction. When the cable-like superconducting conductor 10 fabricated in this way is exposed to a lateral alternating magnetic field, a large eddy current loss occurs. For example, with a solid copper core material with a diameter of 3 mm, the measured eddy current loss is approximately 1.42 W / m under an alternating magnetic field with a peak value of 100 mT and a frequency of 65.44 Hz.

[0029] In the cable-shaped superconducting conductor 10 according to the present invention, illustrated in Figure 1, a stranded wire 1 made by twisting together relatively thin strands is used as the core material. This reduces eddy current loss in the core material. For example, in a stranded wire (Litz wire) with a diameter of approximately 3.1 mm, made by twisting together 50 insulated strands 11 with a diameter of 0.3 mm, the measured eddy current loss is approximately 6.87 mW / m under an AC magnetic field with a peak value of 100 mT and a frequency of 65.44 Hz.

[0030] In the present invention, the diameter of the strands 11 of the stranded wire 1, which is made by twisting together relatively thin strands, can be, for example, about 0.3 mm or less, taking into consideration the strand diameter of the stranded wire in the embodiments described later, which is about 0.3 mm to about 0.1 mm. Similarly, the diameter of the stranded wire 1 can be, for example, about 5 mm or less, taking into consideration the diameter of the core material in the embodiments described later, which is about 2.8 mm to about 3.5 mm.

[0031] <Reducing AC losses in superconducting tape wires> Due to its wide shape, the superconducting tape wire 2 experiences significant AC losses when exposed to an AC magnetic field in the lateral direction (or, if the superconducting tape wire extends longitudinally, in the direction intersecting the longitudinal direction) and perpendicular to the wide surface of the tape (for example, measured values ​​show 3.82 W / m under an AC magnetic field with a peak value of 100 mT and a frequency of 65.44 Hz). In a superconducting conductor formed by bundling many superconducting tape wires 2 together, the AC losses also increase in proportion to the number of wires.

[0032] Here, as illustrated in Figure 1, if a tape-shaped superconducting wire 2 (superconducting tape wire) is spirally wound around the core material along its longitudinal direction, the portion of the superconducting tape wire 2 that is exposed to the alternating magnetic field in the lateral direction and perpendicular to the tape surface within a unit length (1m) is shortened, thus reducing AC losses.

[0033] More preferably, if the superconducting tape wire 2, which is spirally wound around the core material along its longitudinal direction, is made into a multifilament, the AC loss in the superconducting tape wire with respect to a lateral AC magnetic field is further reduced. The superconducting wire 2 illustrated in Figure 1 is a multifilament superconducting wire 2 (2A, 2B, 2C) illustrated in Figures 3-5, in which the superconducting layer 22 is made into a multifilament. The insulating portion 23 is arranged between the multiple superconducting layers 22, 22 and electrically insulates the multiple superconducting layers 22, 22. Depending on the configuration of the superconducting wire 2, a connecting portion 24 and conductive layers 25 (25a, 25b) may be arranged on the superconducting wire 2, but these configurations are omitted from the illustration in Figure 1.

[0034] In particular, if the superconducting tape wire 2, which is spirally wound around the core material along its longitudinal direction, is a superconducting wire 2B equipped with a conductive layer 25a as exemplified in Figure 4, the robustness is improved compared to the superconducting wire 2A as exemplified in Figure 3. As will be described later with reference to Figure 4, the conductive layer 25a functions as a current diversion layer that bypasses the current flowing through the superconducting layer 22 when an abnormality occurs in the superconducting layer 22.

[0035] To more effectively reduce AC losses in a lateral AC magnetic field using a superconducting wire 2B equipped with a conductive layer 25a that reduces AC losses and improves robustness, it is desirable to rapidly attenuate the coupling current 99 flowing through the superconducting wire 2B via the conductive layer 25a. To rapidly attenuate the coupling current 99, it is desirable to shorten the coupling time constant. Since the coupling time constant is proportional to the square of the length of the coupling current 99, it is desirable to shorten the length of the coupling current 99 in order to shorten the coupling time constant.

[0036] In the cable-shaped superconducting conductor to be fabricated, as illustrated in Figure 1(A), if the diameter of the core material is relatively large and the winding angle θ of the superconducting tape wire 2(2B) is relatively small, the length of the coupled current 99 becomes long, the coupling time constant increases, and it becomes impossible to effectively reduce AC losses with respect to the lateral AC magnetic field. In addition, such a cable-shaped superconducting conductor has a low current density and insufficient flexibility for winding.

[0037] In contrast, in the cable-shaped superconducting conductor 10 according to the present invention, preferably, as illustrated in Figure 1(B), the superconducting tape wire 2(2B) is wound spirally around a core material of a relatively small diameter at a relatively large winding angle θ so that the length of the coupled current 99 is shortened. This shortens the coupling time constant, allows the coupled current 99 to be rapidly attenuated, and further reduces the AC loss in the superconducting tape wire 2(2B) when it is spirally wound around the core material. Furthermore, this makes it possible to obtain the high current density and flexibility necessary for applications in which the cable-shaped superconducting conductor 10 is wound to create a winding.

[0038] coupling time constant τ c The coupling time constant is proportional to the square of the length of the eddy current (coupling current). Therefore, if the superconducting tape wire 2(2B) is wound around the core material in such a way that the length of the coupling current 99 flowing in a loop inside the superconducting tape wire 2(2B) is shortened, the coupling time constant is shortened, the coupling current can be rapidly attenuated, and the AC loss in the superconducting tape wire 2(2B) is further reduced. In the cable-shaped superconducting conductor 10 according to the present invention, the method of winding the superconducting tape wire 2(2B) around the core material in such a way that the length of the coupling current 99 is shortened is to wind the superconducting tape wire 2(2B) spirally around a core material of a relatively small diameter, and to increase the winding angle θ of the superconducting tape wire 2(2B) when winding the superconducting tape wire 2(2B) spirally around the core material. As a result, the length of the coupling current 99 flowing in a loop inside the superconducting tape wire 2(2B) is shortened.

[0039] In this invention, the relatively small diameter of the core material can be, for example, about 5 mm or less, taking into account the diameter of the core material in the embodiments described later, which is about 2.8 mm to about 3.5 mm. Similarly, the relatively large winding angle θ can be, for example, about 45 degrees or more, taking into account the winding angle of the superconducting tape wire 2 in the embodiments described later, which is about 55 degrees.

[0040] Assuming that the superconducting tape wire 2 is to be wound spirally around the core material, winding angles θ of 0 degrees or 90 degrees are the easiest to wind, while if it is exactly 45 degrees, the superconducting tape wire 2 will twist, making it difficult to wind. This value of 45 degrees for the winding angle θ is a boundary value for winding angles, and it is easier to wind if it is smaller than this and as close to 0 degrees as possible, or larger than this and as close to 90 degrees as possible. As illustrated in Figure 1(B), in order to shorten the length of the coupled current 99, the superconducting tape wire 2 is wound spirally around the core material at a relatively large winding angle θ. That is, as illustrated in the embodiment described later, it is good to wind the superconducting tape wire 2 spirally around the core material at an angle larger than the boundary value of the winding angle θ, which is 45 degrees.

[0041] <Prevention of a decrease in critical current> When the superconducting tape wire 2 is wound spirally around a core material with a relatively small diameter (for example, about 5 mm or less) at a relatively large winding angle θ (for example, about 45 degrees or more), the superconducting tape wire 2 becomes prone to bending at the point where it touches the strands of the stranded wire 1, which may reduce the critical current of the superconducting tape wire 2.

[0042] In the cable-shaped superconducting conductor 10 according to the present invention, in addition to having the configuration described above, the irregularities (steps) on the outer circumference of the stranded wire 1 are further reduced by employing the following configurations i) to iv) individually or in combination. This further prevents a decrease in the critical current of the superconducting tape wire 2, in addition to the reduction of losses described above.

[0043] i) Reduce the diameter of the strands that make up stranded wire 1. The diameter should be approximately 0.3 mm or less, preferably approximately 0.2 mm or less. ii) Twist the strands together in the same direction. iii) Twist the strands together with the same twist pitch. iv) The outer periphery of stranded wire 1 is covered with a flexible layer and smoothed. The layer is formed using resin or metal.

[0044] [First Embodiment] <Superconducting conductor> Figure 2 is a schematic diagram showing the configuration of a superconducting conductor 10A according to the first embodiment of the present invention. (A) is a perspective view of the superconducting conductor 10A, and (B) is a side view of the superconducting conductor 10A. In the illustrated embodiment, the direction of the Y axis is the longitudinal direction of the stranded wire 1, and the directions of the X axis and Z axis are the radial direction (short direction) of the stranded wire 1.

[0045] The superconducting conductor 10A(10) according to the first embodiment comprises a stranded wire 1 having a plurality of strands 11 twisted together, and a tape-shaped superconducting wire 2 having a superconducting layer formed on the surface of a flexible substrate and being spirally wound around the stranded wire 1 along its longitudinal direction.

[0046] The stranded wire 1 is formed by twisting together a plurality of individual wires 11. Exemplarily, the diameter of the individual wires 11 is approximately 0.3 mm or less, and the diameter of the stranded wire 1 is approximately 5 mm or less. Preferably, the diameter of the individual wires 11 is approximately 0.2 mm or less. In the illustrated embodiment, the diameter of the individual wires 11 is approximately 0.1 mm. The individual wires 11 are formed using a metal with high electrical conductivity (low electrical resistivity), such as copper. Preferably, an insulating layer (not shown) is formed on the surface of the individual wires 11 using an insulating material such as enamel, thereby insulating each individual wire 11.

[0047] The superconducting tape wire 2 is a tape-shaped superconducting wire that is spirally wound around the stranded wire 1 along its longitudinal direction. The superconducting tape wire 2 has a flexible substrate 21 and a superconducting layer 22 formed on the surface of the substrate 21. In the illustrated embodiment, the superconducting tape wire 2 is wound around the stranded wire 1 with the superconducting layer 22 facing inward. In this embodiment, the superconducting layer 22 is made using a high-temperature superconducting material. The superconducting tape wire 2 will be described later with reference to Figures 3 to 5.

[0048] According to the superconducting conductor 10A(10) of the first embodiment, the core material is a stranded wire 1 having a plurality of strands 11 twisted together, the diameter of the strands 11 is approximately 0.3 mm or less, and the diameter of the stranded wire 1 is approximately 5 mm or less. This reduces eddy current loss in the stranded wire 1 which is the core material.

[0049] To reduce AC losses in the superconducting tape wire 2, preferably the winding angle of the superconducting tape wire 2, i.e., the angle θ between the longitudinal direction of the superconducting wire 2 and the longitudinal direction of the stranded wire 1, is about 45 degrees or more and less than about 90 degrees. In addition, if the superconducting tape wire 2 is made into a multifilament as illustrated in Figures 3 to 5, the AC losses in the superconducting tape wire 2 are further reduced.

[0050] To prevent a decrease in the critical current in the superconducting tape wire 2, the diameter of the strands 11 constituting the stranded wire 1 is small. For example, the diameter of the strands 11 is about 0.3 mm or less, preferably about 0.2 mm or less. Preferably, multiple strands 11 are twisted together in the same direction, and preferably, multiple strands 11 are twisted together with the same twist pitch.

[0051] <Superconducting Tape Wire> Figures 3 to 5 show the configurations of various superconducting tape wires 2 provided by the superconducting conductor 10A according to the first embodiment of the present invention. Figure 3 is a schematic perspective view showing the configuration of the superconducting wire 2A according to the first embodiment. Figure 4 is a schematic perspective view showing the configuration of the superconducting wire 2B according to the second embodiment. Figure 5 is a schematic perspective view showing the configuration of the superconducting wire 2C according to the third embodiment. In the illustrated embodiments, the direction of the Y axis is the longitudinal direction of the superconducting wire 2, the direction of the X axis is the short direction of the superconducting wire 2, and the direction of the Z axis is the thickness direction of the superconducting wire 2.

[0052] In all of the superconducting wires 2A, 2B, and 2C shown in Figures 3 to 5, multiple superconducting layers 22 are arranged in parallel along the short-side direction of the substrate 21. The superconducting wires 2A, 2B, and 2C shown in Figures 3 to 5 are called multifilament superconducting wires.

[0053] The first embodiment of the superconducting wire 2A(2) illustrated in Figure 3 comprises a substrate 21, a plurality of superconducting layers 22, an insulating portion 23, and a plurality of connecting portions 24.

[0054] The substrate 21 is formed in a tape shape using, for example, a nickel-based alloy or stainless steel. For example, Hastelloy® can be used as the material for the substrate 21. The substrate 21 is flexible, and as shown in Figure 2, the superconducting wire 2A(2) is used wound in a spiral shape.

[0055] An intermediate layer (not shown) is formed on the surface of the substrate 21 as needed, which serves as the base for the superconducting layer 22. As the material for the intermediate layer, a material can be used whose physical properties, such as thermal expansion coefficient and lattice constant, are intermediate between those of the substrate 21 and the superconductor constituting the superconducting layer 22. For example, LaMnO3 can be used as the material for the intermediate layer. In this embodiment, an intermediate layer is formed on the surface of the substrate 21, and in this description, the substrate 21 with the intermediate layer formed on its surface is collectively referred to as the substrate 21.

[0056] The superconducting layer 22 conducts current superconductively in the superconducting wire 2A. In this embodiment, in order to reduce AC losses, the superconducting layer 22 is multifilamentized and formed on the surface of the substrate 21. The superconducting layer 22 is stretched in the longitudinal direction of the substrate 21, and multiple superconducting layers 22 are arranged in parallel in the short direction of the substrate 21. Exemplarily, the superconducting layer 22 is formed using REBCO high-temperature superconductor, which is a ceramic. REBCO has the chemical formula REBa2Cu3O 7-δ This is a copper oxide superconductor having a compositional formula represented by (RE being a rare earth element such as Y, Gd, Eu, or Sm). In the following description, the multifilamented superconducting layer 22 will be referred to as the superconducting filament 22, or simply as the filament 22 or simply the superconducting layer 22.

[0057] The insulating portion 23 extends in the longitudinal direction of the substrate 21 and is arranged between a plurality of superconducting layers 22, 22, electrically insulating the plurality of superconducting layers 22, 22. Exemplarily, in this embodiment, the insulating portion 23 is formed as a groove that exposes the surface of the substrate 21 by, for example, three-dimensional patterning of the superconducting layer 22 by a known photolithography process. In this embodiment, the superconducting wire 2A comprises a plurality of insulating portions 23, each insulating portion 23 is arranged between a plurality of superconducting layers 22, 22 arranged in parallel.

[0058] The connecting portion 24 is arranged in the insulating portion 23 along the longitudinal direction of the substrate 21 and electrically connects multiple adjacent superconducting layers 22, 22 in a superconducting manner. The superconducting wire 2A is provided with multiple connecting portions 24 in the insulating portion 23 along the longitudinal direction of the substrate 21. In this embodiment, the connecting portion 24 is formed integrally with the superconducting layer 22 using the same superconductor as the superconducting layer 22.

[0059] By superconductively connecting multiple adjacent superconducting layers 22, 22 with the connecting portion 24, the superconductive current distribution of the current flowing through the superconducting layers 22 is improved, and the robustness of the superconducting wire 2A is enhanced. In other words, even if a local transition to a normal conducting state occurs in a certain superconducting layer 22 for some reason, the connecting portion 24 superconductively bridges multiple adjacent superconducting layers 22, 22, and by distributing the current from the superconducting layer 22 that has transitioned to a normal conducting state to the adjacent superconducting layer 22, a quench of the entire superconducting wire 2A is prevented.

[0060] Exemplary, the length (width) of the superconducting wire 2A along its short side is about 2 mm to about 4 mm, preferably about 1 mm to about 4 mm. The length (width) of a single multifilamented superconducting layer 22 along its short side is preferably about 0.4 mm to about 1 mm, more preferably about 0.1 mm to about 1 mm. Exemplary, the overall thickness of the superconducting wire 2A, including the substrate 21 and the superconducting layer 22, is in the range of about 150 μm to about 50 μm, preferably in the range of about 50 μm to about 30 μm. Since the superconducting wire 2A is used wound in a spiral shape, more preferably the overall thickness of the superconducting wire 2A, including the substrate 21 and the superconducting layer 22, is less than about 30 μm.

[0061] The superconducting wire 2B(2) of the second embodiment illustrated in Figure 4 differs from the superconducting wire 2A of the first embodiment illustrated in Figure 3 in that it further comprises a conductive layer 25a(25) covering the superconducting layer 22, the insulating portion 23, and the connecting portion 24. The configuration of the superconducting wire 2B of the second embodiment, as described below, is the same as that of the superconducting wire 2A of the first embodiment unless otherwise specified, so redundant explanations will be omitted.

[0062] In a second embodiment, the superconducting wire 2B(2) further comprises a conductive layer 25a(25) covering the superconducting layer 22, the insulating portion 23, and the connecting portion 24. In the illustrated embodiment, the conductive layer 25a is formed to cover not only the superconducting layer 22, but also the superconducting layer 22, the insulating portion 23, and the connecting portion 24. The conductive layer 25a functions as a current diversion layer that bypasses the current flowing through the superconducting layer 22 when an abnormality occurs in the superconducting layer 22. Exemplarily, the conductive layer 25a is formed of copper. In the illustrated embodiment, the insulating portion 23 is formed as a groove whose bottom surface reaches the surface of the substrate 21, and the groove is filled with copper that functions as the conductive layer 25a.

[0063] The superconducting wire 2B of the second embodiment has improved robustness compared to the superconducting wire 2A of the first embodiment, due to the inclusion of a conductive layer 25a.

[0064] According to the superconducting wire 2B of the second embodiment, the same AC loss reduction effect as the superconducting wire 2A of the first embodiment can be obtained in a limited, but practically sufficient, operating frequency range.

[0065] Similar to the first embodiment, the superconducting wire 2B of the second embodiment can be wound spirally along the axis of the stranded wire 1 which is the core material to form the superconducting conductor 10.

[0066] The superconducting wire 2C(2) of the third embodiment illustrated in Figure 5 differs from the superconducting wire 2A of the first embodiment illustrated in Figure 3 in that it further comprises a conductive layer 25b(25) covering the superconducting layer 22. The configuration of the superconducting wire 2C of the third embodiment, as described below, is the same as that of the superconducting wire 2A of the first embodiment unless otherwise specified, so redundant explanations will be omitted.

[0067] In a third embodiment, the superconducting wire 2C(2) further comprises a conductive layer 25b(25) covering the superconducting layer 22. In the illustrated embodiment, the conductive layer 25b is formed to cover only the superconducting layer 22, without covering the insulating portion 23 and the connecting portion 24. The conductive layer 25b functions as a current diversion layer that bypasses the current flowing through the superconducting layer 22 when an abnormality occurs in the superconducting layer 22. Exemplarily, the conductive layer 25b is formed of copper. In the illustrated embodiment, the insulating portion 23 is formed as a groove that exposes the surface of the substrate 21, but the conductive layer 25b is formed to cover only the superconducting layer 22, and the groove is not filled with copper that functions as the conductive layer 25b.

[0068] According to the third embodiment of the superconducting wire 2C, the same AC loss reduction effect as the superconducting wire 2A of the first embodiment can be obtained.

[0069] The superconducting wire 2C of the third embodiment has improved robustness compared to the superconducting wire 2A of the first embodiment by including a conductive layer 25b. More specifically, the rise in hot spot temperature can be suppressed by diverting the current from the superconducting layer 22 to the conductive layer 25b provided above the superconducting layer 22.

[0070] Similar to the first embodiment, the superconducting wire 2C of the third embodiment can be wound spirally along the axis of the stranded wire 1 which is the core material to form a superconducting conductor 10.

[0071] As described above, the superconducting conductor 10A(10) according to the first embodiment can provide a superconducting conductor with reduced losses.

[0072] According to the superconducting conductor 10A(10) of the first embodiment, the core material is a stranded wire 1 having a plurality of strands 11 twisted together, the diameter of the strands 11 is about 0.3 mm or less, and the diameter of the stranded wire 1 is about 5 mm or less. This makes it possible to reduce eddy current loss in the stranded wire 1 which is the core material. By making the diameter of the strands 11 constituting the stranded wire 1 small, to about 0.3 mm or less, it is possible to prevent a decrease in the critical current of the superconducting tape wire 2.

[0073] The fact that the diameter of the strand 11 is approximately 0.3 mm or less takes into account the strand diameter of the stranded wire in the embodiment described later, which is approximately 0.3 mm to approximately 0.1 mm. Similarly, the fact that the diameter of the stranded wire 1 is approximately 5 mm or less takes into account the diameter of the core material in the embodiment described later, which is approximately 2.8 mm to approximately 3.5 mm.

[0074] Furthermore, in the superconducting conductor 10A according to the first embodiment, preferably, the angle θ between the longitudinal direction of the superconducting wire 2 and the longitudinal direction of the stranded wire 1 is about 45 degrees or more and less than about 90 degrees. This makes it possible to reduce AC losses in the superconducting tape wire 2.

[0075] The angle θ between the longitudinal direction of the superconducting wire 2 and the longitudinal direction of the stranded wire 1, i.e., the winding angle θ, being approximately 45 degrees or more and less than approximately 90 degrees, takes into account the winding angle of approximately 55 degrees for the superconducting tape wire 2 in the embodiment described later.

[0076] Furthermore, in the superconducting conductor 10A according to the first embodiment, preferably, a plurality of strands 11 are twisted together in the same direction. This smooths the outer circumference of the stranded wire 1 and prevents a decrease in the critical current in the superconducting tape wire 2.

[0077] Furthermore, in the superconducting conductor 10A according to the first embodiment, preferably, multiple strands 11 are twisted together with the same twist pitch. This smooths the outer circumference of the stranded wire 1 and prevents a decrease in the critical current in the superconducting tape wire 2.

[0078] [Second Embodiment] The configuration of the superconducting conductor 10B(10) according to the second embodiment is the same as that of the superconducting conductor 10A(10) according to the first embodiment, unless otherwise specified, so redundant explanations will be omitted.

[0079] Figure 6 is a schematic diagram showing the configuration of the superconducting conductor 10B according to a second embodiment of the present invention. (A) is a side view of the superconducting conductor 10B, and (B) is a cross-sectional view of the superconducting conductor along the 5B-5B line shown in (A).

[0080] The superconducting conductor 10B(10) according to the second embodiment differs from the superconducting conductor 10A according to the first embodiment in that it further comprises a flexible smoothing layer 3A(3) positioned between the stranded wire 1 and the tape-shaped superconducting wire 2, covering the periphery of the stranded wire 1 along its longitudinal direction. The smoothing layer 3A(3) is formed using resin or metal and covers the periphery of the stranded wire 1 in a cylindrical or spiral shape.

[0081] In the illustrated embodiment, the diameter of the strand 11 is approximately 0.3 mm, six strands 11 are twisted together in a Z-twist to form one primary strand, and seven primary strands are twisted together in an S-twist to form one strand 1.

[0082] Furthermore, in the illustrated embodiment, multiple tape-shaped superconducting wires 21 and 22 are partially overlapped and spirally wound around the stranded wire 1 along its longitudinal direction. Superconducting wire 21 is wound around the stranded wire 1 in an S-winding pattern, and superconducting wire 22 is wound around the stranded wire 1 in a Z-winding pattern. In other words, in the illustrated embodiment, multiple superconducting wires 21 and 22 are spirally wound around the stranded wire 1 along its longitudinal direction in different orientations.

[0083] As described above, the superconducting conductor 10B(10) according to the second embodiment can provide a superconducting conductor with reduced losses.

[0084] According to the superconducting conductor 10B(10) of the second embodiment, a flexible smoothing layer 3A(3) is further provided between the stranded wire 1 and the tape-shaped superconducting wire 2. This smooths the outer circumference of the stranded wire 1 and prevents a decrease in the critical current in the superconducting tape wire 2.

[0085] Furthermore, according to the superconducting conductor 10B(10) of the second embodiment, multiple superconducting wires 21, 22 are spirally wound around the stranded wire 1. This makes it possible to increase the amount of current that flows through a single superconducting conductor 10B.

[0086] [Other forms] Although the present invention has been described above with reference to specific embodiments, the present invention is not limited to the embodiments described above.

[0087] In the embodiments described above, in the superconducting conductor 10, various forms of superconducting tape wires 2 (2A, 2B, 2C) illustrated in Figures 3 to 5 are spirally wound around the stranded wire 1 along its longitudinal direction. However, the superconducting tape wires wound around the stranded wire 1 are not limited to these forms. In the superconducting conductor 10, various forms of superconducting tape wires 2 (2D, 2E, 2F) illustrated in Figures 7(A) to (C), for example, may be spirally wound around the stranded wire 1 along its longitudinal direction.

[0088] In the superconducting wire 2D(2) illustrated in (A), the superconducting layer 22 is uniformly formed on the surface of the substrate 21. The superconducting wire 2D in the embodiment shown in (A) is called a monofilament superconducting wire. In the superconducting wire 2E(2) illustrated in (B), the superconducting layer 22a is divided into narrow filaments to form a multifilament. In the superconducting wire 2F(2) illustrated in (C), a copper current divider layer 27 is further formed on the surface of the multifilament superconducting layer 22a as a current divider layer for conductors. The superconducting wires 2E and 2F in the embodiments shown in (B) and (C) are also multifilament superconducting wires.

[0089] In other embodiments, the cable-shaped superconducting conductor 10 may further include a normal conducting member that electrically connects the tape-shaped superconducting wire 2 to at least one strand 11 of the stranded wire 1. This allows current to be diverted to the stranded wire 1, which is the conductive core material, and improves the robustness of the superconducting conductor 10. The normal conducting member can be placed at the longitudinal end of the superconducting conductor 10 or in the middle of the superconducting conductor 10 in the longitudinal direction.

[0090] In yet another embodiment, these multiple normal conducting members are arranged to minimize, preferably zero, the integral of the lateral magnetic field with respect to the superconducting conductor in the superconducting conductor section between adjacent normal conducting members. This makes it possible to suppress eddy current losses due to eddy currents flowing between the strands 11 in the stranded wire 1, and coupling losses due to coupling currents flowing between the strands 11 of the stranded wire 1 and the superconducting wire 2, which are caused by the presence of normal conducting members.

[0091] In the embodiment described above, the superconducting tape wire 2 is wound around the stranded wire 1 with the superconducting layer 22 facing inward, but the superconducting tape wire 2 may also be wound around the stranded wire 1 with the superconducting layer 22 facing outward.

[0092] In the embodiment described above, the superconducting conductor 10 is used as the primary conductor, and a secondary conductor may be fabricated by twisting together multiple strands of this primary conductor. This increases the current capacity of the fabricated superconducting conductor. A tertiary conductor may be fabricated by further twisting together multiple strands of such a secondary conductor.

[0093] In the second embodiment described above, the tape-shaped superconducting wires 21 and 22 are wound spirally around the stranded wire 1 along its longitudinal direction, in different orientations. In this case, the multiple superconducting wires 21 and 2 are partially overlapped when wound around the stranded wire 1. However, if the multiple superconducting wires 21 and 22 are wound spirally around the stranded wire 1 along its longitudinal direction in the same orientation, the multiple superconducting wires 21 and 2 can be wound around the stranded wire 1 without overlapping.

[0094] In the second embodiment described above, the superconducting conductor 10B(10) includes a flexible smoothing layer 3A(3) between the stranded wire 1 and the tape-shaped superconducting wire 2. In the second embodiment, the smoothing layer 3A(3) is arranged to cover the circumference of the stranded wire 1, which has a diameter of approximately 5 mm or less and is formed by twisting together individual wires 11 with a diameter of approximately 0.3 mm or less, similar to the first embodiment, along the longitudinal direction. However, the form of the stranded wire 1 is not limited to this, as long as the outer circumference of the stranded wire 1 is smoothed by the smoothing layer 3A. Furthermore, even if the superconducting conductor 10 includes smoothing layers 3B, 3C as illustrated in the following embodiments instead of the smoothing layer 3A, the form of the stranded wire 1 is not limited, as long as the outer circumference of the stranded wire 1 is smoothed by the smoothing layers 3B, 3C.

[0095] In other words, if the superconducting conductor 10 is equipped with a smoothing layer 3, as long as the outer circumference of the stranded wire 1 is smoothed by the smoothing layer 3, the decrease in the critical current of the superconducting tape wire 2 can be reduced or prevented, without being limited to the form of the stranded wire 1. Furthermore, the effect of reducing or preventing the decrease in critical current achieved by the superconducting conductor 10 being equipped with a smoothing layer 3 is achieved independently of the reduction in losses in the superconducting conductor 10.

[0096] Furthermore, as illustrated in the following embodiment, if the bending angle of the superconducting tape wire 2 along the outer circumference of the stranded wire 1 is less than or equal to a predetermined angle, the decrease in the critical current of the superconducting tape wire 2 can be reduced or prevented without providing a smoothing layer 3, regardless of the configuration of the stranded wire 1. According to the embodiment, the predetermined angle for the bending angle of the superconducting tape wire 2 along the outer circumference of the stranded wire 1 is 12 degrees or less.

[0097] [Examples] The following examples illustrate the features of the present invention. In the examples and comparative examples described below, the core material on which the tape-shaped superconducting wire 2 is wound is constructed using various stranded wires 1, superconducting wires 2, and smoothing layers 3 (3A, 3B, 3C) to create or simulate the creation of a cable-shaped superconducting conductor 10. Table 1 shows a list of superconducting conductors that were created or simulated. Of these, Comparative Example 1 is a superconducting conductor that was simulated, while the others are superconducting conductors that were actually created. The numbers in parentheses in the wire diameter column of the table represent the diameter after covering with heat shrink tubing or winding with Hastelloy tape. PEY in the same column means that the diameter has increased slightly due to winding with Tetron thread.

[0098] In Example 1, the tape-shaped superconducting wire 2 was a multifilament superconducting wire 2F (with 5 filaments) as shown in Figure 7(C). In Examples 2-6 and Comparative Examples 1-3, the tape-shaped superconducting wire 2 was a monofilament superconducting wire 2D as shown in Figure 7(A). In Examples 1-6, stranded wire (litz wire) made of insulated strands twisted together, as shown in Table 2, was used. [Table 1] [Table 2]

[0099] The reduction in losses was verified based on Example 1, Comparative Examples 1 and 2. The reduction in critical current was verified based on Examples 2 to 6 and Comparative Example 3.

[0100] <Verification regarding losses> In Example 1, Comparative Examples 1 and 2 described below, the losses were measured for the fabricated superconducting conductor and the prepared flat superconducting wire 2. From the losses obtained from the measurements, we confirmed how the measured loss values ​​change depending on the configuration of the superconducting conductor. [Example 1]

[0101] In Example 1, a superconducting conductor 10 was fabricated by covering the stranded wire 1 with a resin tube and then spirally winding a superconducting tape wire 2 around its surface. Model IZ05 was used for the stranded wire 1. For the tape-shaped superconducting wire 2, a multifilament superconducting wire 2F in the configuration shown in Figure 7(C) was used. [Comparative Example 1]

[0102] In Comparative Example 1, a superconducting conductor was assumed in which a solid copper single wire with a diameter of 3 mm was used as the core material, and a superconducting tape wire 2 was directly wound spirally around this core material. For the tape-shaped superconducting wire 2, a monofilament superconducting wire 2D in the manner shown in Figure 7(A) was used. [Comparative Example 2]

[0103] As Comparative Example 2, a tape-shaped superconducting wire 2(2D) identical to that used in Comparative Example 1 was prepared. The loss of the superconducting wire 2 was measured in a flat state, without being spirally wound around the core material. When measuring the loss, the direction of the magnetic field applied to the superconducting tape wire 2 was perpendicular to the tape surface.

[0104] Figure 8 is a graph showing the results of verifying the loss reduction effect. (a) shows the loss measured for the superconducting conductor 10 fabricated in Example 1. (b) shows the loss measured for the superconducting conductor assumed as Comparative Example 1. In (b), the lower part of the bar graph shows the loss in the core material, and the upper part shows the loss in the superconducting tape wire (SC). (c) shows the loss measured for the flat tape-shaped superconducting wire 2 (2D) prepared as Comparative Example 2.

[0105] In Comparative Example 1, the losses in the core material (eddy current loss) and the losses in the superconducting tape wire (AC loss) were measured separately. Specifically, the eddy current loss was measured for a solid copper single wire with a diameter of 3 mm as the loss in the core material, and the AC loss in the superconducting tape wire was measured for a superconducting tape wire 2 that was directly wound in a spiral around a GFRP core material with a diameter of 3 mm.

[0106] The loss measurements in Example 1 shown in (a) include eddy current losses in the stranded wire 1, which is the core material, but these are extremely small and can be ignored. Therefore, the loss measurements in Example 1 were determined to be approximately equal to the AC losses in the superconducting tape wire 2.

[0107] In the measurement values ​​for Comparative Example 1 shown in (b), it was determined that the reason for the large loss due to the core material in the lower part of the bar graph was that the core material was solid rather than stranded wire 1.

[0108] Regarding the loss in the superconducting tape wire 2, the reason why the measured value for Comparative Example 1 shown in the upper part of the bar graph in (b) is smaller than the measured value for Comparative Example 2 shown in (c) was determined to be the effect of spirally winding the superconducting tape wire 2 around the core material, that is, the effect of shortening the portion of the superconducting tape wire 2 that is exposed to the alternating magnetic field in the lateral direction and perpendicular to the tape surface within a unit length (1m).

[0109] The reason why the loss in Example 1 shown in (a) is smaller than the loss in Comparative Example 1 shown in the upper part of the bar graph in (b) was determined to be the effect of making the superconducting tape wire 2 a multifilament.

[0110] <Verification regarding critical current> In Examples 2 to 6 and Comparative Example 3 described below, the electric field-current characteristics were measured for each fabricated superconducting conductor 10. The electric field-current characteristics were measured before and after the superconducting tape wire 2 was spirally wound around the core material. From the electric field-current characteristics obtained from the measurements, it was confirmed whether a degradation of the critical current occurred before and after winding the superconducting tape wire 2. The value of the critical current was defined as the current value at which the breakdown of the superconducting state was confirmed. [Example 2]

[0111] Figure 9 is a schematic diagram showing the structure of the superconducting conductor 10C(10) fabricated in Example 2. (A) is a side view of the superconducting conductor 10C, and (B) is a cross-sectional view of the superconducting conductor 10C along the 7B-7B line shown in (A).

[0112] In Example 2, a superconducting conductor 10C was fabricated by directly winding a superconducting tape wire 2 in a spiral pattern around a stranded wire 1. For the stranded wire 1, model IZ02 was used, with a strand diameter of 0.3 mm and a finished diameter of 2.8 mm. In model IZ02, six strands 11 were twisted together in a Z-twist to form one primary stranded wire, and seven primary stranded wires were twisted together in an S-twist to form one stranded wire 1.

[0113] Figure 10 shows the measurement results of the electric field-current characteristics of the superconducting conductor 10C(10) fabricated in Example 2. According to the measurement results shown in Figure 10, in the superconducting conductor 10C of Example 2, the breakdown of the superconducting state was confirmed at approximately half the current value compared to the superconducting tape wire 2 alone before spiral winding. When comparing at the critical current, it was confirmed that the superconducting conductor 10C of Example 2 was able to exhibit approximately half the performance of the superconducting tape wire 2 alone.

[0114] Detailed observations by the inventors revealed that in the superconducting conductor 10C, air gaps 8 were observed between the stranded wire 1 and the superconducting tape wire 2, and bending of the superconducting tape wire 2 along the outer circumference of the stranded wire 1 was observed near several of these air gaps 8. From this, it was presumed that the bending of the superconducting tape wire 2 was caused by irregularities on the outer circumference of the stranded wire 1, and from a comparison with the superconducting conductor 90 fabricated in Comparative Example 3 described later, it was presumed that the bending of the superconducting tape wire 2 along the outer circumference of the stranded wire 1 caused a deterioration in the critical current.

[0115] In this embodiment 2, the stranded wire of model number IZ02 used had a diameter of 0.3 mm for each strand 11, which was relatively thicker than the 0.1 mm diameter of the strands 11 of model numbers IZ05 or IZ06 used in embodiments 5 and 6 described later. Furthermore, in the stranded wire of model number IZ02, the twisting direction differed between when the strands 11 were twisted to form the primary stranded wire and when the primary stranded wire was twisted to form the final stranded wire 1.

[0116] Next, in this second embodiment, the degree to which irregularities on the outer circumference of the stranded wire 1 are acceptable in relation to the degree of degradation of the critical current was confirmed by calculating the bending angle of the superconducting tape wire 2 along the outer circumference of the stranded wire 1.

[0117] If we arrange 0.3mm diameter wires along a circumference of 8.8mm calculated from the core material's diameter of 2.8mm, approximately 29 wires can be placed. In other words, the core material is assumed to be a 29-sided polygon, not a perfect circle. If we further assume that it is a regular 29-sided polygon, its exterior angle is approximately 12 degrees. If we consider that the superconducting tape wire is wrapped around the regular 29-sided core material and bends, the bending angle is assumed to be 12 degrees.

[0118] As shown in the measurement results in Figure 10, it was confirmed that in Example 2, approximately half the performance was achieved compared to the superconducting tape wire 2 alone. In this case, the bending angle of the superconducting tape wire 2 along the outer circumference of the stranded wire 1 was assumed to be 12 degrees. Therefore, according to Example 2, it was confirmed that if the bending angle of the superconducting tape wire 2 is 12 degrees or less, approximately half the performance can be achieved in terms of the degree of degradation of the critical current compared to the superconducting tape wire 2 alone. [Example 3]

[0119] Figure 11 is a schematic diagram showing the configuration of the superconducting conductor 10D(10) fabricated in Example 3. (A) is a side view of the superconducting conductor 10D, and (B) is a cross-sectional view of the superconducting conductor 10D along the line 9B-9B shown in (A).

[0120] In Example 3, a tape-shaped Hastelloy® was spirally wound around the stranded wire 1 as a smoothing layer 3B(3), and then a superconducting tape wire 2 was spirally wound around its surface to produce a superconducting conductor 10D. The same IZ02 model was used for the stranded wire 1 as in Example 2. Two strands of metallic Hastelloy tape were wound spirally in parallel around the stranded wire 1. The superconducting tape wire 2 was wound in a Z-direction, while the Hastelloy tape was wound in an S-direction.

[0121] Figure 12 shows the measurement results of the electric field-current characteristics of the superconducting conductor 10D(10) fabricated in Example 3. According to the measurement results shown in Figure 12, in the superconducting conductor 10D according to Example 3, the breakdown of the superconducting state was confirmed at approximately half the current value compared to the superconducting tape wire 2 alone before spiral winding. When comparing at the critical current, it was confirmed that the superconducting conductor 10D according to Example 3 was able to exhibit approximately half the performance of the superconducting tape wire 2 alone. [Example 4]

[0122] Figure 13 is a schematic diagram showing the structure of the superconducting conductor 10E(10) fabricated in Example 4. (A) is a side view of the superconducting conductor 10E, and (B) is a cross-sectional view of the superconducting conductor 10E along the 11B-11B line shown in (A).

[0123] In Example 4, a resin tube was used as the smoothing layer 3A(3) to cover the stranded wire 1, and a superconducting tape wire 2 was then spirally wound around its surface to create a superconducting conductor 10D. The stranded wire 1 used was the same as in Example 2, model number IZ02.

[0124] Figure 14 shows the measurement results of the electric field-current characteristics of the superconducting conductor 10E(10) fabricated in Example 4. According to the measurement results shown in Figure 14, in the superconducting conductor 10E according to Example 4, the breakdown of the superconducting state was confirmed at approximately the same current value as the superconducting tape wire 2 alone before spiral winding. From this, it was confirmed that by using a resin tube as the smoothing layer 3A, there was no substantial degradation of the critical current before and after winding the superconducting tape wire 2. [Example 5]

[0125] Figure 15 is a schematic diagram showing the structure of the superconducting conductor 10F(10) fabricated in Example 5. (A) is a side view of the superconducting conductor 10F, and (B) is a cross-sectional view of the superconducting conductor 10F along the 13B-13B line shown in (A).

[0126] In Example 5, a yarn (or fiber) made of Tetron (registered trademark) was used as a smoothing layer 3C(3) to cover the periphery of the twisted wire 1, and a superconducting tape wire 2 was then spirally wound around its surface to create a superconducting conductor 10F. Tetron is made of polyester resin.

[0127] Unlike the IZ02 model used in Examples 2-4, the stranded wire 1 used the IZ05 model, which has a strand diameter of 0.1 mm and a finished diameter of 2.8 mm. The 0.1 mm diameter of the strand 11 of the IZ05 model was thinner than the 0.3 mm diameter of the strand 11 of the IZ02 model used in Examples 2-4. With the IZ05 model, the twisting direction was the same S-twist, both when twisting the strands 11 to form the primary stranded wire and when twisting the primary stranded wire to form the final stranded wire 1. The twist pitch was also the same at 50 mm, both when twisting the strands 11 to form the primary stranded wire and when twisting the primary stranded wire to form the final stranded wire 1.

[0128] Figure 16 shows the measurement results of the electric field-current characteristics of the superconducting conductor 10F(10) fabricated in Example 5. According to the measurement results shown in Figure 16, in the superconducting conductor 10F according to Example 5, the breakdown of the superconducting state was confirmed at approximately the same current value as the superconducting tape wire 2 alone before spiral winding. From this, it was confirmed that by using Tetron thread as the smoothing layer 3C, there was no substantial degradation of the critical current before and after winding of the superconducting tape wire 2, regardless of the type of stranded wire 1. [Example 6]

[0129] Figure 17 is a schematic diagram showing the configuration of the superconducting conductor 10G(10) fabricated in Example 6. (A) is a side view of the superconducting conductor 10G, and (B) is a cross-sectional view of the superconducting conductor 10G along the 15B-15B line shown in (A).

[0130] In Example 6, a superconducting conductor 10G was fabricated by omitting the smoothing layer 3C from the superconducting conductor 10F fabricated in Example 5. In Example 6, the superconducting conductor 10G was fabricated by directly winding the superconducting tape wire 2 spirally around the stranded wire 1. Unlike the superconducting conductor 10F fabricated in Example 5, the superconducting conductor 10G was not covered with Tetron thread around the stranded wire 1.

[0131] In Example 6, the stranded wire 1 used was model IZ06, with a strand diameter of 0.1 mm and a finished diameter of 3.2 mm. The 0.1 mm diameter of the strands 11 of model IZ06 is the same as the 0.1 mm diameter of the strands 11 of model IZ05 used in Example 5. In model IZ06, as with model IZ05, the twisting direction was the same S-twist whether the strands 11 were twisted to form the primary stranded wire or the primary stranded wire was twisted to form the final stranded wire 1. The twist pitch was also the same at 50 mm whether the strands 11 were twisted to form the primary stranded wire or the primary stranded wire was twisted to form the final stranded wire 1.

[0132] If we arrange 0.1 mm diameter wires along a circumference of 10 mm calculated from the core material's diameter of 3.2 mm, approximately 100 wires can be placed. In other words, the core material is assumed to be a 100-sided polygon, not a perfect circle. If we further assume that this is a regular 100-sided polygon, its exterior angle is approximately 3.6 degrees. If we consider that the superconducting tape wire is wrapped around the regular 100-sided core material and bends, even if bending occurs, the bending angle is assumed to be 3.6 degrees.

[0133] Figure 18 shows the measurement results of the electric field-current characteristics of the superconducting conductor 10G(10) fabricated in Example 6. According to the measurement results shown in Figure 18, in the superconducting conductor 10G according to Example 6, the breakdown of the superconducting state was confirmed at approximately the same current value as the superconducting tape wire 2 alone before spiral winding. From this, it was confirmed that when the diameter of the strands 11 is thinner than approximately 0.1 mm, and the twisting direction and twisting pitch are the same when twisting the strands 11 to form a primary stranded wire, and when twisting the primary stranded wire to form the final stranded wire 1, there is no substantial degradation of the critical current before and after winding the superconducting tape wire 2, even without the smoothing layer 3.

[0134] Next, in this embodiment 6, the degree to which irregularities on the outer circumference of the stranded wire 1 are permissible in relation to the degree of degradation of the critical current was confirmed by calculating the bending angle of the superconducting tape wire 2 along the outer circumference of the stranded wire 1.

[0135] As shown in the measurement results in Figure 18, in Example 6, it was confirmed that there was no substantial degradation of the critical current before and after winding the superconducting tape wire 2, even without the smoothing layer 3. In this case, the bending angle of the superconducting tape wire 2 along the outer circumference of the stranded wire 1 was assumed to be 3.6 degrees. Therefore, according to Example 6, it was confirmed that if the bending angle of the superconducting tape wire 2 is 3.6 degrees or less, there is no substantial degradation of the critical current even without the smoothing layer 3. [Comparative Example 3]

[0136] Figure 19 schematically shows the structure of the superconducting conductor 90 fabricated as Comparative Example 3. (A) is a side view of the superconducting conductor 90, and (B) is a cross-sectional view of the superconducting conductor 90 along the line 17B-17B shown in (A).

[0137] In Comparative Example 3, a glass fiber reinforced plastic (GFRP) with a flat surface was used as the core material 9, and a superconducting conductor 90 was fabricated by directly winding a superconducting tape wire 2 spirally around the GFRP core material 9. Since the core material 9 was not flexible, the superconducting conductor 90 was also not flexible.

[0138] Figure 20 shows the measurement results of the electric field-current characteristics of the superconducting conductor 90 fabricated in Comparative Example 3. According to the measurement results shown in Figure 20, in the superconducting conductor 90 of Comparative Example 3, the breakdown of the superconducting state was confirmed at approximately the same current value as the superconducting tape wire 2 alone before spiral winding. From this, it was confirmed that when the surface of the core material 9 is flat, no deterioration of the critical current occurs before and after winding the superconducting tape wire 2 along the longitudinal direction of the core material 9. [Explanation of symbols]

[0139] 1 stranded wire 2(2A, 2B, 2C, 2D, 2E, 2F) Tape-shaped superconducting wires (superconducting tape wires) 3(3A,3B,3C) Smoothing layer 8 void 9 Core material 10(10A,10B,10C,10D,10E,10F,10G) Cable-shaped superconducting conductor 11 strands 21 circuit boards 22(22a) Superconducting layer 23 Insulation part 24 Connection part 25(25a,25b) Conductive layer 27 Copper distribution layer 90. Cable-shaped superconducting conductor fabricated as a comparative example. 98. Sustained eddy currents 99 Combined current

Claims

1. A stranded wire having multiple metal strands twisted together, A tape-shaped superconducting wire having a superconducting layer formed on the surface of a flexible substrate, and being spirally wound around the stranded wire along its longitudinal direction, Equipped with, The diameter of the metal strand is 0.3 mm or less, and the diameter of the stranded wire is 5 mm or less. A superconducting conductor in which the angle between the longitudinal direction of the superconducting wire and the longitudinal direction of the stranded wire is 45 degrees or more and less than 90 degrees.

2. The superconducting conductor according to claim 1, wherein the bending angle of the superconducting wire along the outer circumference of the stranded wire is 12 degrees or less.

3. The superconducting conductor according to claim 1 or 2, wherein the plurality of metal strands are twisted together in the same direction.

4. The superconducting conductor according to any one of claims 1 to 3, wherein the plurality of metal strands are twisted together with the same twist pitch.

5. The superconducting conductor according to any one of claims 1 to 4, further comprising a flexible smoothing layer disposed between the stranded wire and the superconducting wire so as to cover the periphery of the stranded wire along its longitudinal direction.

6. The superconducting conductor according to claim 5, wherein the smoothing layer is formed using resin or metal and covers the stranded wire in a cylindrical or spiral shape.

7. The superconducting wire comprises a plurality of such superconducting wires, The superconducting conductor according to any one of claims 1 to 6, wherein the plurality of superconducting wires are spirally wound around the stranded wire along its longitudinal direction.

8. The superconducting conductor according to claim 7, wherein the multiple superconducting wires are spirally wound around the stranded wire in a longitudinal direction, with different orientations.

9. In the aforementioned superconducting wire, The superconducting conductor according to any one of claims 1 to 8, wherein the plurality of superconducting layers are extended in the longitudinal direction of the substrate and arranged in parallel in the short direction of the substrate.

10. The superconducting conductor according to any one of claims 1 to 9, further comprising a normal conducting member for electrically connecting the superconducting wire and at least one of the metal strands of the stranded wire.

11. A winding comprising a superconducting conductor as described in any one of claims 1 to 10.

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