JP2014192114A - Superconductive cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a superconductive cable capable of performing high-frequency power transmission of 1 kHz or higher.SOLUTION: A superconductive cable comprises a former, a superconductive conductor layer formed by winding a thin-film superconductive wire rod 120 on the outer periphery of the former, an electric insulation layer formed on the outer periphery of the superconductive conductor layer and a shield layer formed by winding the thin-film superconductive wire rod 120 on the electric insulation layer, is used in high-frequency power transmission of 1 kHz or higher and meets the condition β≤10×α, where α, W/m, is the sum of the AC loss of a superconductive phase 123 contained in the superconductive conductor layer and the AC loss of the superconductive phase 123 contained in the shield layer in high-frequency power transmission under the condition I (frequency=10 kHz, effective value of the flowing current=2 kArms), and β, W/m, is the sum of the eddy current loss of a wire rod protective layer 125 contained in the superconductive conductor layer and the eddy current loss of the wire rod protective layer 125 contained in the shield layer in high-frequency power transmission under the condition I.

Description

  The present invention relates to a superconducting cable used for high-frequency power transmission of 1 kHz or more.

  A high-frequency electric power of 1 kHz (1000 Hz) or more may be used for steel reforming (for example, high-frequency heat-kneading). For example, Patent Document 1 discloses a technique of using a high-frequency induction heating device at a frequency of 3 kHz, a power of 443 kW (443000 W), and a voltage of 667 V in hot forging of steel. When using such a high-frequency induction heating device, power at a commercial frequency of 50 Hz or 60 Hz is converted into high-frequency power of 1 kHz or more by a conversion facility in the factory, and the high-frequency power is heated by high-frequency induction heating using a normal conductive bus bar or the like. The device is transmitting power.

JP 2003-138315 A

  For power transmission at high frequencies and large currents, there is a problem that the AC resistance of the normal conducting bus bar increases and the transmission loss becomes very large. In order to reduce this transmission loss, the normal conducting bus bar must be made very large. In particular, depending on the device to be operated, high-frequency and large-current power having a frequency of 1 kHz or more and an effective value of the energization current of 1 kArms (rms; root mean square value) or more may be used. Therefore, power transmission loss cannot be ignored even at short distances in the factory. Here, a superconducting cable is known that has less power transmission loss than a normal conducting bus bar, and it is expected that the power transmission loss can be reduced by using the superconducting cable for power transmission at a high frequency and a large current. However, the application of superconducting cables to power transmission at a high frequency of 1 kHz or higher has never been studied.

  The present invention has been made in view of the above circumstances, and one of its purposes is to provide a superconducting cable capable of performing high-frequency power transmission of 1 kHz or higher.

  Superconducting cables have been developed with a focus on how to cut power transmission losses in long-distance power transmission at commercial frequencies of 50-60 Hz. For this reason, there is no idea of applying a superconducting cable to short-distance power transmission at high frequencies, and what has become a problem in application has not been studied. Then, when this inventor simulated high frequency transmission of 1 kHz or more using a superconducting cable, it turned out that the transmission loss of a superconducting cable may become larger than the transmission loss of a normal conducting bus bar. The present inventor has found that the cause is a problem of eddy current loss generated in the normal conducting portion included in the superconducting wire used in the superconducting conductor and shield layer of the superconducting cable. As superconducting wires, a superconducting wire in which a filament of a superconducting phase is embedded in a stabilizing material such as Ag (hereinafter referred to as a filament-type superconducting wire), and a superconducting phase and a stabilizing layer such as Ag are formed on a substrate. And a superconducting wire (hereinafter referred to as a thin film superconducting wire). The stabilizing material (stabilizing layer) serves as a detour for current when the superconducting phase can no longer maintain the superconducting state, and is usually required to have good conductivity. However, in high-frequency power transmission, it has been found that the stabilization layer has good conductivity, conversely, increases eddy current loss.

  Next, the inventor reexamined the configuration of the filament type superconducting wire and the thin film superconducting wire from the viewpoint of whether or not there is room for reducing the eddy current loss. The filament type superconducting wire is produced mainly by a method called a tube-in-powder method. In this method, a plurality of Ag pipes filled with powder to be a superconducting phase are prepared, and the filament type superconducting wire is produced by placing them in a large diameter Ag pipe and drawing and heat-treating them. Yes. That is, in the filament type superconducting wire, since the portion other than the filament of the superconducting phase is composed of Ag, there is no room for reducing the eddy current loss in the filament type. On the other hand, in a thin film superconducting wire, a thin film superconducting phase and an Ag stabilizing layer are laminated on a substrate, and the outer periphery thereof is covered with a wire protecting layer. Since the wire protective layer is expected to have a role as a bypass layer for an accident current while protecting the superconducting phase, it is usually made of a highly conductive material. However, as a result of the study by the present inventors, an excessive accident current does not flow in the high-frequency / high-current power transmission in the factory, and therefore it is not necessary to positively give the wire protective layer a role as a bypass layer. I found out. Based on the above knowledge, this invention is prescribed | regulated below.

A superconducting cable of the present invention includes a former, a superconducting conductor layer formed by winding a thin film superconducting wire having the following configuration on the outer periphery of the former, an electric insulating layer formed on the outer periphery of the superconducting conductor layer, and a thin film having the following configuration And a shield layer formed by winding a superconducting wire on an electrical insulating layer. The superconducting cable is used for high-frequency power transmission of 1 kHz or more and satisfies β ≦ 10 × α.
“Thin-film superconducting wire”: a laminate of a base material, an oxide superconducting phase, and a normal conducting stabilization layer, and a wire protective layer covering the outer periphery of the laminate with a material having a lower conductivity than the stabilizing layer; , A thin film superconducting wire.
“Α”: Sum of the AC loss of the superconducting phase included in the superconducting conductor layer and the AC loss of the superconducting phase included in the shield layer in high-frequency power transmission under the following condition I (unit: W / m).
“Β”: Total of eddy current loss of the wire protective layer included in the superconducting conductor layer in high-frequency power transmission under the following condition I and eddy current loss of the wire protective layer included in the shield layer (unit: W / m).
“Condition I”: frequency 10 kHz (10 × 10 ³ Hz), effective current 2 kArms (2 × 10 ³ Arms).

  According to the superconducting cable of the present invention, high-frequency power transmission of 1 kHz or more can be performed with less power transmission loss than the normal conductive bus bar.

1 is a perspective view showing a schematic configuration of a superconducting cable according to Embodiment 1. FIG. It is sectional drawing which shows schematic structure of a thin film superconducting wire.

[Description of Embodiment of the Present Invention]
First, the contents of the embodiment of the present invention will be listed and described.

(1) A superconducting cable according to an embodiment of the present invention includes a former, a superconducting conductor layer formed by winding a thin film superconducting wire having the following configuration on the outer periphery of the former, and an electrical insulating layer formed on the outer periphery of the superconducting conductor layer. And a shield layer formed by winding a thin film superconducting wire having the following configuration on an electrical insulating layer, and is a superconducting cable that is used for high-frequency power transmission of 1 kHz or more and that satisfies β ≦ 10 × α.
“Thin-film superconducting wire”: a laminate of a base material, an oxide superconducting phase, and a normal conducting stabilization layer, and a wire protective layer covering the outer periphery of the laminate with a material having a lower conductivity than the stabilizing layer; , A thin film superconducting wire.
“Α”: Sum of the AC loss of the superconducting phase included in the superconducting conductor layer and the AC loss of the superconducting phase included in the shield layer in high-frequency power transmission under the following condition I (unit: W / m).
“Β”: Total of eddy current loss of the wire protective layer included in the superconducting conductor layer in high-frequency power transmission under the following condition I and eddy current loss of the wire protective layer included in the shield layer (unit: W / m).
“Condition I”: frequency 10 kHz (10 × 10 ³ Hz), effective current 2 kArms (2 × 10 ³ Arms).

  If the eddy current loss β when performing high-frequency and large-current power transmission under the above condition I is 1000% or less of the AC loss α, the power transmission loss of the superconducting cable is the power transmission loss of the normal conducting busbar under the same power transmission conditions. Small enough compared to The eddy current loss β is more preferably 100% or less, further preferably 10% or less, and most preferably 1% or less of the AC loss α.

(2) Examples of the superconducting cable according to the embodiment of the present invention include a form where β ≦ 0.1 × α.

  If the eddy current loss β when performing high-frequency power transmission under the above condition I is 10% or less of the AC loss α, the power transmission loss of the superconducting cable is extremely higher than the power transmission loss of the normal conductive bus bar under the same power transmission conditions. It can be said that it is small. As already described, it is most preferable that the eddy current loss β is 1% or less of the AC loss α.

(3) Examples of the superconducting cable according to the embodiment of the present invention include an embodiment in which the thickness of the wire protective layer provided in the thin film superconducting wire is 20 μm or less.

  If the thickness of the wire protective layer is 20 μm or less, eddy currents hardly flow through the wire protective layer, so that eddy current loss in the wire protective layer can be reduced.

(4) As the superconducting cable of the embodiment of the present invention, mention is made of an embodiment in which the conductivity of the wire protective layer at the refrigerant temperature for maintaining the superconducting phase in the superconducting state is 100 MS / m (100 × 10 ⁶ S / m) or less. Can do.

  If the electrical conductivity of the wire protective layer is 100 MS / m or less, eddy currents hardly flow through the wire protective layer, so that eddy current loss in the wire protective layer can be reduced. For example, the electrical conductivity of stainless steel is about 2 MS / m at the temperature of liquid nitrogen (about 77 K), which is a typical refrigerant for superconducting cables. In addition, the electrical conductivity of Cu at the temperature of liquid nitrogen is about 500 MS / m.

(5) Examples of the superconducting cable according to the embodiment of the present invention include a form in which the thickness of the base material provided in the thin film superconducting wire is 100 μm or less.

  When the thickness of the substrate is 100 μm or less, eddy current loss in the substrate when a magnetic field acts on the substrate can be reduced.

(6) As the superconducting cable of the embodiment of the present invention, the thin film superconducting wire constituting the superconducting conductor layer is wound on the former with the surface on the substrate side facing inward in the radial direction of the superconducting cable. The thin film superconducting wire constituting the shield layer may be wound on the electrical insulating layer with the base-side surface facing outward in the radial direction of the superconducting cable.

  In a superconducting cable comprising a superconducting conductor layer and a shield layer positioned radially outward of the superconducting cable relative to the superconducting conductor, a magnetic field is formed between the superconducting phase of the superconducting conductor layer and the superconducting phase of the shield layer. The Therefore, by setting the substrate of the thin film superconducting wire constituting the superconducting conductor layer in a state where the superconducting cable is directed inward in the radial direction of the superconducting cable, it is possible to avoid a magnetic field from acting on the substrate, and eddy current loss in the substrate Can be suppressed. Similarly, by setting the base material of the thin film superconducting wire constituting the shield layer to be in the radially outward direction of the superconducting cable, it can be avoided that a magnetic field acts on the base material, and eddy current loss in the base material Can be suppressed.

  When the superconducting conductor layer is formed by winding thin film superconducting wires in multiple layers, the magnetic field does not act on the base material of the innermost layer (first layer) thin film superconducting wire, but the thin film superconducting wire outside the innermost layer A magnetic field acts on the substrate. Similarly, when the shield layer is formed by winding thin film superconducting wires in multiple layers, a magnetic field does not act on the substrate of the outermost thin film superconducting wire, but a magnetic field is applied to the substrate of the thin film superconducting wire inside the outermost layer. Works.

[Details of the embodiment of the present invention]
A specific example of the superconducting cable according to the embodiment of the present invention will be described with reference to the drawings. In addition, this invention is not limited to these illustrations, is shown by the claim, and intends that all the changes within the claim, the meaning equivalent, and the range are included.

<Embodiment 1>
≪Overall structure≫
The superconducting cable 1 of this embodiment shown in FIG. 1 is used when power is transmitted at a high frequency of 1 kHz or more over a very short distance (for example, 100 m or less) such as in a factory. The superconducting cable 1 shown in this example is a superconducting cable in which a plurality of cable cores 10 (here, three cores) are twisted and housed in one heat insulating tube 20, that is, a so-called multi-core batch type superconducting cable. Of course, the cable core 10 of the superconducting cable 1 may be single-core, two-core, four-core or more. The superconducting cable 1 is characterized in that the superconducting conductor layer 12 and the shield layer 14 included in the cable core 10 are both composed of the thin film superconducting wire 120 and can be used for high-frequency power transmission of 1 kHz or more. . Hereinafter, each configuration will be described in more detail.

≪Insulated pipe≫
The heat insulating tube 20 is a double structure tube composed of an inner tube 21 and an outer tube 22, and is a vacuum heat insulating structure in which the space between the inner tube 21 and the outer tube 22 is evacuated. The inner tube 21 is filled with a refrigerant such as liquid nitrogen, and the cable core 10 is cooled by this refrigerant and maintained in a superconducting state. Between the inner tube 21 and the outer tube 22, a heat insulating material 23 such as a super insulation and a spacer (not shown) that keeps a distance between both the tubes 21 and 22 are arranged. On the outer periphery of the outer tube 22, an anticorrosion layer 24 made of a material having excellent corrosion resistance such as polyvinyl chloride is formed.

≪Cable core≫
Each cable core 10 includes a former 11, a superconducting conductor layer 12, an electrical insulating layer 13, a shield layer 14, and a core protective layer 15 in order from the center.

(Former)
In addition to functioning as a support for the superconducting conductor layer 12, the former 11 is used in the superconducting cable 1 as a flow path for diverting a large current generated in the event of an abnormality such as a short circuit or a ground fault. For the former 11, a solid body or a hollow body (tubular body) formed of a normal conductive material such as copper or aluminum can be used. Here, the former 11 shown in FIG. 1 is a solid body formed by twisting a plurality of copper wires each having an insulation coating such as polyvinyl chloride (PVC) or enamel. By being a stranded wire structure, it has excellent bending characteristics, and when the superconducting cable 1 is used for AC power transmission, eddy current loss can be reduced.

  A cushion layer may be provided on the outer periphery of the former 11. The cushion layer can be formed by, for example, winding an insulating tape made of insulating paper such as kraft paper, or semi-synthetic insulating paper (for example, PPLP (registered trademark of PP)). . By providing the cushion layer, the superconducting conductor layer 12 can be easily formed, and the superconducting conductor layer 12 can be prevented from being damaged by the copper wire constituting the former 11.

(Superconducting conductor layer, shield layer)
The superconducting conductor layer 12 and the shield layer 14 are configured by spirally winding the thin film superconducting wire 120 into a single layer or multiple layers. Each of the superconducting conductor layer 12 and the shield layer 14 shown in FIG. 1 has a multi-layer structure in which superconducting wire layers formed by spirally winding a thin film superconducting wire 120 are stacked in layers (superconducting conductor layer 12 : 4 layers, shield layer 14: 3 layers). Between the layers of each superconducting wire layer, an interlayer insulating layer 120i wound with insulating paper such as kraft paper is formed. Both the superconducting conductor layer 12 and the shield layer 14 are allowed to include the interlayer insulating layer 120i in addition to the portion made of the thin film superconducting wire 120.

  The number of superconducting wires constituting the superconducting conductor layer 12 and the number of superconducting wires can be selected according to a desired set current value (current capacity). Further, the number of superconducting wires constituting the shield layer 14 and the number of superconducting wires can be appropriately selected according to the superconducting conductor layer 12.

[Thin film superconducting wire]
As shown in FIG. 2, the thin film superconducting wire 120 used for the superconducting conductor layer 12 and the shield layer 14 includes a base material 121, an intermediate layer 122, a superconducting phase 123, a stabilization layer 124, and a wire material protective layer 125.

First, the superconducting phase 123 serving as a conductive path of the thin film superconducting wire 120 is an oxide high-temperature superconductor capable of using liquid nitrogen as a refrigerant, for example. Specifically, RE-based oxides containing rare earth elements such as Y, Ho (holmium), and Gd (gadolinium) can be used for the superconducting phase 123. The RE-based oxide superconducting phase is typically (RE) Ba ₂ Cu ₃ O _x called RE123, and specific compositions include YBCO, HoBCO, and GdBCO. In addition, an oxide containing Bi (bismuth) such as Bi2223 can be used for the superconducting layer 123.

  The thickness of the superconducting phase 123 can be appropriately selected according to the current capacity required for the superconducting cable 1. For example, the thickness of the superconducting phase 123 may be 1 μm or more. On the other hand, since the superconducting phase 123 is brittle, if the superconducting phase 123 is made too thick, the superconducting phase 123 may be cracked. Thus, the thickness of the superconducting phase 123 is preferably 5 μm or less.

  The substrate 121 is typically made of a metal material. For example, a magnetic material, particularly a magnetic base material made of a ferromagnetic material can be used. The magnetic substrate is excellent in the orientation of the RE-based oxide superconducting phase, which will be described later, easily forms the superconducting phase, and is excellent in the manufacturability of the thin film superconducting wire. Examples of the ferromagnetic material include nickel alloys such as iron, cobalt, nickel, and Ni—W alloy, iron-containing materials such as silicon steel, permalloy, ferrite, and ferromagnetic stainless steel (for example, SUS430). In addition, a non-magnetic material such as Hastelloy (registered trademark) can be used as the constituent material of the base material 121. A nonmagnetic material is preferable because generation of eddy currents in the substrate 121 can be suppressed.

  The thickness of the substrate 121 is preferably 50 μm to 100 μm. By setting the thickness of the base 121 to 50 μm or more, the strength of the thin film superconducting wire 120 can be ensured. Moreover, the eddy current loss in the base material 121 can be reduced by setting the thickness of the base material to 100 μm or less. From the viewpoint of reducing eddy current loss, the thickness of the substrate 121 is preferably 100 μm or less.

The intermediate layer 122 is a layer for adjusting the crystal orientation of the superconducting phase 123 when the superconducting phase 123 is formed on the substrate 121. Moreover, it is also a layer for preventing the element contained in the base material 121 from diffusing into the superconducting phase 123 and degrading the superconducting phase 123. As the material of the intermediate layer 122, an insulator made of an oxide such as YSZ (yttria stabilized zirconia), MgO, or CeO ₂ can be used. The intermediate layer 122 may have a multilayer structure. For example, the intermediate layer 122 may be a three-layer intermediate layer 122 made of CeO ₂ —YSZ—CeO ₂ .

  The thickness of the intermediate layer 122 is preferably 10 to 2000 nm. When the intermediate layer 122 has a multilayer structure, the thickness of each layer is preferably 1 to 1000 nm, and the total thickness of all layers is preferably 50 to 2000 nm.

  The stabilization layer 124 is a layer for preventing the superconducting phase 123 from reacting with other members and not exhibiting superconducting characteristics. Examples of the material of the stabilization layer 124 include Ag, Pt, Au, and alloys thereof. In view of cost, the stabilization layer 124 is preferably composed of Ag.

  The stabilization layer 124 illustrated in FIG. 2 covers the entire outer periphery of the laminate of the base material 121, the intermediate layer 122, and the superconducting phase 123. Considering the role of the stabilization layer 124, the stabilization layer 124 may be formed at least on the upper surface of the superconducting phase 123 (upper surface on the paper surface).

  The thickness of the stabilization layer 124 is preferably 1 μm to 20 μm. By setting the thickness of the stabilization layer 124 to 1 μm or more, the stabilization layer 124 can be sufficiently provided with a function of stabilizing the superconducting phase 123. On the other hand, by setting the thickness of the stabilization layer 124 to 20 μm or less, the amount of eddy current loss in the stabilization layer 124 can be kept low.

  The wire material protective layer 125 is a layer having a function of protecting the superconducting phase 1 in a configuration disposed inside the wire material protective layer 125. Here, in addition to the function of protecting the superconducting phase, the wire material protective layer of the thin film superconducting wire used in the conventional superconducting cable used at commercial frequencies has a function as a bypass layer when an accident current flows. There is a technical idea. On the other hand, in the superconducting cable 1 of the present invention used at a high frequency, the wire protection layer 125 is not actively required to have a function as an accident current bypass layer, that is, the eddy current does not easily flow through the wire protection layer 125. Is adopted. By doing so, the eddy current loss in the wire protective layer 125 is reduced, and the power transmission loss of the superconducting cable 1 is reduced.

  In order to make it difficult for the eddy current to flow through the wire protective layer 125, the wire protective layer 125 may be made of a material having a lower conductivity than the stabilizing layer 124 described above. For example, a non-conductive material such as glass fiber, or a low conductive material such as stainless steel or a Cu—Ni alloy is suitable for the wire protective layer 125. In order to make it difficult for an eddy current to flow through the wire protective layer 125, it is also effective to make the wire protective layer 125 thin.

  The wire protection layer 125 is preferably formed by plating if the material can be plated (for example, Cu—Ni alloy). When the wire protection layer 125 is formed of a material unsuitable for plating such as stainless steel or glass fiber, a tape material made of the material is attached to the outer periphery of the laminate (base material 121, intermediate layer 122, superconducting phase 123). The wire protective layer 125 may be formed. Note that solder can be used for pasting.

  The conductivity of the wire protective layer 125 is preferably 500 MS / m or less, more preferably 200 MS / m or less, 100 MS / m or less, 10 MS / m or less, and 5 MS / m or less. On the other hand, the thickness of the wire protective layer 125 is preferably 100 μm or less, more preferably 50 μm or less, 20 μm or less, 10 μm or less, or 5 μm or less. In order to securely protect the superconducting phase 123 with the wire protective layer 125, the thickness of the wire protective layer 125 is preferably 1 μm or more.

  If the conductivity of the wire protective layer 125 is set higher within the above range, the eddy current loss in the wire protective layer 125 can be kept low by reducing the thickness of the wire protective layer 125. Further, if the conductivity of the wire protection layer 125 is set to be lower within the above range, the wire protection layer 125 can be increased even if the thickness of the wire protection layer 125 is increased in order to improve the function of protecting the superconducting phase 123. Eddy current loss is difficult to increase.

(Electrical insulation layer)
The electrical insulating layer 13 is formed by winding an insulating tape such as the above-described kraft paper or semi-synthetic insulating paper on the superconducting conductor layer 12. An inner semiconductive layer is provided by winding carbon paper or metallized paper directly on the superconducting conductor layer 12, or carbon paper or metallized paper is wound directly on the wound layer of the insulating tape. An outer semiconductive layer can be provided. The electrical insulating layer 13 can be provided with the semiconductive layer.

(Core protective layer)
The core protective layer 15 is provided on the outer periphery of the shield layer 14 and mechanically protects the shield layer 14. The core protective layer 15 can be formed by winding an insulating tape such as the above-described kraft paper, semi-synthetic insulating paper, or cloth tape.

≪Simulation Example≫
The superconducting cable 1 was used to determine the AC loss of the superconducting phase 123 and the eddy current loss of the wire material protective layer 125 when high-frequency power transmission of 1 kHz or higher was performed. Table 1 shows the specifications of the superconducting cable 1 subjected to this simulation.

  In the superconducting cable 1 shown in Table 1, the number of superconducting conductor layers 12 and shield layers 14 is one. The thin film superconducting wire 120 constituting the superconducting conductor layer 12 is wound with the surface on the base 121 side facing inward in the radial direction (former 11), and the thin film superconducting wire 120 constituting the shield layer 14 is It is assumed that the substrate 121 is wound in a state where the surface on the substrate 121 side is directed outward in the radial direction.

  Moreover, the electrical conductivity of the wire protective layer 125 of the superconducting wire 120 is set to 1000 MS / m. This conductivity is a value that exceeds the conductivity of Ag (about 500 MS / m) at the temperature of liquid nitrogen (about 77 K).

  Furthermore, the thickness of the wire protective layer 125 of the thin film superconducting wire 120 is 100 μm. Since the width and thickness of the thin film superconducting wire 120 shown in Table 1 are 2.2 mm and 0.33 mm, respectively, the portion excluding the wire protecting layer 125 (base material 121, intermediate layer 122, superconducting phase 123, and stabilization) The width and thickness of the laminate comprising the layer 124 are 2.0 mm and 0.13 mm, respectively.

  In this simulation, it was assumed that a high-frequency current having a frequency f of 10 kHz (10000 Hz), an angular velocity ω of 62832 rad / s, and an effective current Iop of 2000 A (peak value Ip of the applied current is 2828 A) was applied. Then, the strength of the magnetic field acting on the superconducting conductor layer 12 and the shield layer 14 is calculated from the energization conditions, and the AC loss of the superconducting phase 123 in the superconducting conductor layer 12 and the shield layer 14 are calculated based on information including the calculation result. The AC loss of the superconducting phase 123 was determined. As a result, the AC loss of the superconducting phase 123 in the superconducting conductor layer 12 was 1.27 W / m, and the AC loss of the superconducting layer 123 in the shield layer 14 was 1.19 W / m. That is, the AC loss (αW / m) of the entire superconducting phase 123 included in the superconducting cable 1 was 2.46 W / m.

  Furthermore, when the eddy current loss of the wire protective layer 125 in the superconducting conductor layer 12 and the eddy current loss of the wire protective layer 125 in the shield layer 14 were obtained based on information such as the strength of the magnetic field, the former was 24.51 W / m, the latter was 23.64 W / m. That is, the eddy current loss (βW / m) of the entire wire rod protective layer 125 included in the superconducting cable 1 was 48.15 W / m.

  From the above results, when the electrical conductivity of the wire protective layer 125 of the thin film superconducting wire 120 exceeds the electrical conductivity of the stabilizing layer 124 (the electrical conductivity of Ag) in high-frequency power transmission of 1 kHz or higher, the wire protective layer 125 eddy current loss (βW / m = 48.15 W / m) is more than 10 times (about 19.5 times) the AC loss (αW / m = 2.46 W / m) of the superconducting phase 123; That is, it was found that β> 10 × α. In this case, the power transmission loss of the superconducting cable 1 is larger than the power transmission loss of the normal conducting bus bar that performs high-frequency power transmission of the same scale as the superconducting cable 1 when the efficiency of the cooling system is 0.06. Incidentally, the power transmission loss of the superconducting cable 1 when the sum of the AC loss and the eddy current loss is about 35 W / m is substantially equal to the power transmission loss of the normal conducting bus bar of the same scale.

  Based on the above results, the AC loss of the entire superconducting phase 123 included in the superconducting cable 1 when the conductivity and thickness of the wire protecting layer 125 are changed, and the vortex of the entire wire protecting layer 125 included in the superconducting cable 1. The current loss was calculated. Table 2 shows the AC loss and Table 3 shows the eddy current loss.

  From the results of Tables 2 and 3, it can be said that both reducing the conductivity of the wire protective layer 125 and reducing the thickness of the wire protective layer 125 contribute to the reduction of eddy current loss in the wire protective layer 125. understood. In Table 2, the AC loss decreases as the thickness of the wire protective layer 125 is decreased because the width and thickness of the thin film superconducting wire 120 change by the thickness of the wire protective layer 125. Further, “0.00” in Table 3 is a small value less than “0.005” and is not “0”.

If these conductivity and thickness are mutually defined, the eddy current loss of the wire protective layer 125 included in the superconducting cable 1 can be reduced to 1/10 or less of the AC loss of the superconducting phase 123 included in the superconducting cable 1. it can. Specifically, when the electrical conductivity of the wire protective layer 125 is γMS / m and the thickness of the wire protective layer 125 is δμm, the eddy current loss (βW / m; Table 3) was found to be 1/10 or less of the AC loss (αW / m; see Table 2) of the superconducting phase 123, that is, β ≦ 0.1 × α. The power transmission loss of such a superconducting cable 1 is extremely small compared to the power transmission loss of a normal conductive bus bar that performs high-frequency power transmission of the same scale.
When γ is 500 MS / m or less, δ is 10 μm or less, when γ is 100 MS / m or less, δ is 20 μm or less, when γ is 50 MS / m or less, δ is 30 μm or less, and when γ is 20 MS / m or less, δ is 50 μm or less When γ is 10 MS / m or less, δ is 70 μm or less, when γ is 5 MS / m or less, δ is 90 μm or less, and when γ is 2 MS / m or less, δ is 100 μm or less

Based on the relationship between the electrical conductivity and thickness of the wire protective layer 125, the eddy current loss (βW / m) of the wire protective layer 125 is set to 1/10 or less of the AC loss (αW / m) of the superconducting phase 123. The relationship between the electrical conductivity and thickness of the wire protective layer 125 that can be expressed by a mathematical expression is as shown in the following formula (1) or formula (2). If the wire material protective layer 125 satisfies this mathematical formula, the superconducting cable 1 with very little power transmission loss can be obtained.
Formula (1) ... Y <= 185 * X- ^0.39
Formula (2) ... Y <= 209 * X- ^0.52
X = conductivity of wire rod protective layer (MS / m), Y = thickness of wire rod protective layer (μm)

  Formula (1) was determined as follows. First, the electrical conductivity (MS / m) of the wire protective layer 125 is taken as the horizontal axis, and the thickness (μm) of the wire protective layer 125 is taken as the vertical axis, with reference to Tables 2 and 3, β> 0.1 × α The minimum thickness of the wire protective layer 125 is plotted on the graph. And the approximate line of the plot was calculated | required with the computer. The approximation (1) is obtained by formulating the approximate line. On the other hand, Expression (2) is an expression of an approximate line of the maximum thickness of the wire protective layer 125 that satisfies β ≦ 0.1 × α with reference to Tables 2 and 3.

  The superconducting cable of the present invention can be suitably used for high-frequency energization of 1 kHz or higher. For example, the superconducting cable of the present invention can be suitably used as a power cable for a high-frequency heating device.

DESCRIPTION OF SYMBOLS 1 Superconducting cable 10 Cable core 11 Former 12 Superconducting conductor layer 13 Electrical insulation layer 14 Shielding layer 15 Core protection layer 20 Heat insulation pipe 21 Inner pipe 22 Outer pipe 23 Heat insulation material 24 Corrosion protection layer 120 Thin film superconducting wire 120i Interlayer insulation layer 121 Base material 122 Intermediate layer 123 Superconducting phase 124 Stabilization layer 125 Wire protection layer

Claims (6)

Forma,
A thin film superconducting wire comprising: a laminate of a base material, an oxide superconducting phase, and a normal conducting stabilization layer; and a wire protective layer covering the outer periphery of the laminate with a material having a conductivity lower than that of the stabilizing layer. A superconducting conductor layer formed by winding the outer periphery of the former,
An electrically insulating layer formed on the outer periphery of the superconducting conductor layer;
A thin film superconducting wire having the above-described configuration, and a shield layer formed by winding the thin film superconducting wire on the electrical insulating layer,
ΑW / m is the sum of the AC loss of the superconducting phase contained in the superconducting conductor layer and the AC loss of the superconducting phase contained in the shield layer in high-frequency power transmission of 1 kHz or higher and in high-frequency power transmission under the following condition I , When the sum of the eddy current loss of the wire protective layer included in the superconducting conductor layer and the eddy current loss of the wire protective layer included in the shield layer in high-frequency power transmission under the following condition I is βW / m, Superconducting cable with ≦ 10 × α.
Condition I: Frequency = 10 kHz, effective value of energization current = 2 kArms.   The superconducting cable according to claim 1, wherein β ≦ 0.1 × α.   The superconducting cable according to claim 1 or 2, wherein the thickness of the wire protective layer is 20 µm or less.   The superconducting cable according to any one of claims 1 to 3, wherein the conductivity of the wire protective layer at a refrigerant temperature that maintains the superconducting phase in a superconducting state is 100 MS / m or less.   The thickness of the said base material is 100 micrometers or less, The superconducting cable as described in any one of Claims 1-4. The thin film superconducting wire constituting the superconducting conductor layer is wound on the former in a state where the surface on the substrate side is directed inward in the radial direction of the superconducting cable,
The thin film superconducting wire constituting the shield layer is wound on the electrical insulating layer in a state where the surface on the base is directed radially outward of the superconducting cable. The superconducting cable according to one item.

Images