JP4634954B2 - Superconducting device - Google Patents

Description

  The present invention relates to a superconducting device.

  The superconducting device is used in various applications such as a magnetic resonance imaging diagnostic device (MRI), a superconducting magnetic energy storage device (SMES), a superconducting current limiter, and the like. It is produced by. In recent years, the development of so-called coated conductors, which are superconducting wires made by growing highly biaxially oriented superconducting thin films such as yttrium-based superconductors, which are excellent in critical current density characteristics in a magnetic field, has been promoted. It has reached the stage of practical use.

However, such a superconducting wire (coated conductor) has a structure different from that of the conventional superconducting wire, the base material is a high resistance base material, and is called an intermediate layer between the base material and the superconducting layer. An oxide layer typified by YSZ (yttrium stabilized zirconia) or CeO ₂ is formed (see, for example, Patent Document 1). In the case of this structure, the base material and the superconducting layer are basically electrically insulated by an insulating intermediate layer. Here, when only the superconducting layer is connected to the connection terminal for current introduction, and the substrate (base material) is not connected to the connection terminal, the potential of the substrate is not fixed, and the superconducting layer and the substrate are not fixed. A large potential difference may occur between them. For this reason, the conventional technology has a risk of causing dielectric breakdown between the superconducting layer and the substrate.
JP 2000-133067 (paragraph 0012)

  The present invention has been made to solve the above-described problems, and connects a superconducting layer and a base material with an intermediate layer of such a superconducting wire (coated conductor) as a boundary, and a substrate (base material). The purpose of this is to fix the potential.

In order to achieve the above object, a superconducting device according to an embodiment of the present invention is formed by sequentially laminating a superconducting layer and a conductive metal layer through an insulating intermediate layer that is electrically insulated on one side of a metal substrate. a superconducting wire consisting of Te, and a connecting portion made of a good conductive metal silver or copper to electrically connect the conductive metal layer and the metal substrate of the superconducting wire at least one end of the superconducting wire The connecting portion is integrated with one end of the superconducting wire opposite to the metal base or the intermediate layer of the conductive metal layer, and the other end overlaps the surface of the plate-like metal terminal. It is connected to .

  According to the present invention, since the superconducting layer and the metal base material are connected with the intermediate layer of the superconducting wire (coated conductor) as a boundary, the potential of the substrate (base material) can be fixed, and the base material and the superconducting layer can be fixed. It is possible to provide a superconducting device that can greatly reduce the possibility of dielectric breakdown without causing an unexpected potential difference therebetween.

  EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated based on drawing. FIG. 1 is a diagram schematically showing the main configuration of the superconducting device according to the first embodiment of the present invention, and FIG. 2 is a diagram of the superconducting wire at the end of the superconducting wire surrounded by a broken line in FIG. It is expanded sectional drawing of the part to which the plate-shaped metal terminal was connected.

  As shown in FIG. 1, a superconducting device 1 according to this embodiment, for example, a superconducting coil, is manufactured by winding a superconducting wire 2 around a winding frame 3. Superconducting wire 2 is integrally connected to a part of plate-like metal terminal 4 at its end. As shown in FIG. 2, the superconducting wire 2 is formed by laminating a superconducting layer 7 and a conductive metal layer 8 in this order on one side of a metal substrate 5 with an intermediate layer 6 interposed therebetween. Such a superconducting wire (coated conductor) 2 is integrally connected to a part of the plate-like metal terminal 4 on one surface of either the metal base 5 or the conductive metal layer 8. The opposite surface of the superconducting wire 2 is connected to the plate-like metal terminal 4 by the respective end portions of the connection plate 9 made of a highly conductive metal.

  Any metal can be used for the plate-like metal terminal 4 as long as it is a metal that can supply current to the superconducting wire 2, but a metal having a low electrical resistivity is preferable. Specific examples of such metals include silver and copper. The shape of the plate-like metal terminal 4 may be any shape as long as current can be supplied to the superconducting wire 2. For example, the plate-like metal terminal is suitable for connection to the superconducting wire 2.

The metal substrate 5 can be appropriately determined depending on the type, material, thickness, etc. of the superconducting wire 2 to be used. Specifically, various metal materials such as silver, platinum, stainless steel, copper, Ni—W alloy, Ni—Fe alloy, and nickel-based alloys such as Hastelloy can be used, and nickel-based alloys are preferable. Although the thickness of the metal base material 5 can be determined according to a use, it is about 50-100 micrometers normally. The metal substrate 5 is usually a high resistance layer.
When the superconducting layer 7 is abnormal, for example, a current flowing in the superconducting layer 7 when the superconducting layer 7 has an abnormality such as a quenching phenomenon due to a temperature rise due to some disturbance or thermal runaway occurs, for example, a highly conductive metal It is commutated (divided) through the connecting plate 9 made of the above, and damage due to burning of the superconducting layer 7 due to Joule heat can be prevented.

The material constituting the intermediate layer 6 is, for example, YSZ (yttrium stabilized zirconia), SrTiO ₃ , MgO, Al ₂ O ₃ , LaAlO ₃ whose thermal expansion coefficient is closer to that of the superconducting layer 7 than the metal substrate 5. An intermediate layer made of a ceramic crystal such as LaGaO ₃ , YAlO ₃ , or ZrO ₂ can be used. Among these, it is preferable to use a material with as much crystal orientation as possible. The intermediate layer 6 normally insulates the metal substrate 5 and the superconducting layer 7. Although the thickness of the intermediate | middle layer 6 can be suitably determined according to a use, it is about 10-800 nm normally.

The superconductor constituting the superconducting layer 7 is a superconductor capable of forming the superconducting layer 7 laminated on the metal substrate 5 via the intermediate layer 6. These superconductors include high temperature superconductors. Examples of the high-temperature superconductor include yttrium-based high-temperature superconductors, such as YBCO-based oxide superconductors, holmium-based high-temperature superconductors, such as HoBCO-based oxide superconductors, RE123 (rare earth elements such as Y, Nd, and Sm) -based superconductors. Body, AB-Cu-O system (where A is one or more elements of Group IIIa elements of the periodic table such as La, Ce, Y, Sc, Yb, and B is periodic table IIa of Sr, Ba, etc.) An oxide superconductor of one or more group elements).
The superconducting layer 7 is formed on the metal substrate 5 via the intermediate layer 6 by, for example, a pulse laser deposition method (PLD method), a metal organic compound deposition method (MOD method), a chemical vapor deposition method (CVD method), or the like. It can be manufactured by forming a thin film of a superconductor such as YBCO. The thickness of such a superconducting layer 7 can be appropriately determined according to the application, but is usually about 1 μm.

Examples of the material of the conductive metal layer 8 include metal materials such as silver, stainless steel, copper, and SUS (for example, SUS304). The thickness of the conductive metal layer 5 can be appropriately determined according to the application, but is usually about 10 to 100 μm, for example, 50 μm.
For example, a silver deposition layer may be formed between the conductive metal layer 8 and the superconducting layer 7. In this case, the thickness of the silver vapor deposition layer can be determined as appropriate, for example, about 10 μm.

The superconducting wire 2 formed by sequentially laminating the superconducting layer 7 and the conductive metal layer 8 on one side of the metal substrate 5 with the intermediate layer 6 interposed therebetween may be a single wire or connected in the middle. It may be. Further, the connection is made even if the conductive metal layers 8 of the superconducting wire 2 are stacked and electrically connected to each other, or the end surfaces of the connecting end portions of the superconducting wire 2 are abutted against each other. In order to cover the connection end portion, for example, another superconducting wire may be disposed and electrically connected to each other with the respective conductive metal layers stacked in opposition to each other.
These superconducting wires 2 may be connected at one place or at two or more places. Furthermore, the connection of the superconducting wire 2 may be a combination of a connection in which the superconducting wires 2 are opposed to each other and a connection in which the superconducting wires 2 are arranged in the same direction (with the end faces butted together). Good.

  Next, the connection plate 9 made of a highly conductive metal will be described. The connection plate 9 made of a highly conductive metal is made of a metal of a highly conductive material such as silver or copper. The connection plate 9 made of a highly conductive metal is connected at one end to the surface of the superconducting wire 2 that is not integrally connected to the plate-like metal terminal 4 of the metal base 5 and the conductive metal layer 8, and the like. It is integrally connected to the plate-like metal terminal 4 at the end. Therefore, the potential of the metal substrate can be fixed by this connection. Further, due to this connection at both ends of the superconducting wire 2, for example, when quenching or thermal runaway occurs, the metal substrate is connected from the superconducting layer 7 through the conductive metal layer 8 via the connection plate 9 made of a highly conductive metal. The current can also be shunted to the material 5 side. Further, the connection plate 9 made of a highly conductive metal can also increase the strength of bonding between the superconducting wire 2 and the plate-like metal terminal 4.

  Superconducting wire 2 (metal base 5 or conductive metal layer 8) and plate-like metal terminal 4, connection plate 9 made of superconducting wire 2 and well-conductive metal, and plate-like metal terminal 4 and well-conductive metal As a method of connecting the connection plate 9, any method can be used as long as they can be electrically connected (connected integrally). For example, the connection can be made using soldering, diffusion bonding, or the like.

For example, when connecting the superconducting wire 2 (the metal substrate 5 or the conductive metal layer 8) and the plate-like metal terminal 4 using soldering, any of the superconducting wire 2 and the plate-like metal terminal 4 to be connected is used. Solder is disposed on one of the connecting portions, the other connecting portion is disposed on the solder so as to overlap each other, and the solder is melted and connected by heating or, optionally, heating under pressure. The same applies to the connection of the superconducting wire 2 and the connection plate 9 made of a highly conductive metal, and the connection between the plate-like metal terminal 4 and the connection plate 9 made of a highly conductive metal by soldering.
The solder to be used can be appropriately determined according to the type of superconducting wire 2, the type of metal substrate 5, the type of conductive metal layer 8, the type of metal substrate, and the like. For example, silver, copper, indium, tin-silver solder, tin-copper solder, tin-lead solder, indium-silver solder, tin-indium solder, tin-bismuth, tin-bismuth-- Solder such as indium solder can be used. The soldering conditions can be determined as appropriate according to the type of solder used.

Further, for example, when connecting the superconducting wire 2 and the plate-like metal terminal 4 using diffusion bonding, the connecting portions of the superconducting wire 2 and the plate-like metal terminal 4 to be connected are arranged to face each other, The connection is made by heating or optionally heating under pressure. The same applies to the connection by diffusion bonding between the superconducting wire 2 and the connection plate 9 made of a highly conductive metal, and the plate metal terminal 4 and the connection plate 9 made of a highly conductive metal.
The conditions for diffusion bonding can be appropriately determined according to the type of superconducting wire 2 to be used, the type of metal substrate 5, the type of conductive metal layer 8, the type of connection plate 9 made of a highly conductive metal, and the like.

Next, the connection structure at the end of the superconducting wire in this embodiment will be described.
The connection structure at the end of the superconducting wire may be integrally connected to a part of the plate-like metal terminal 4 on the conductive metal layer 8 side of the superconducting wire 2 as shown in FIG. As shown in 2 (b), the superconducting wire 2 may be integrally connected to a part of the plate-like metal terminal 4 on the metal base 5 side. The connection plate 9 made of a highly conductive metal is not connected to the plate-like metal terminal 4 of the superconducting wire 2 (the surface of the conductive metal layer 8 or the metal substrate 5), and the surface of the plate-like metal terminal 4 Are connected together by overlapping each end.

The connection structure at the end of the superconducting wire shown in FIG. 2 (a) is such that a current flows from the plate metal terminal 4 to the superconducting layer 7 via the conductive metal layer 8 without using the connection plate 9 made of a highly conductive metal. Flows. Therefore, the potential of the metal substrate 5 is fixed by connecting the metal substrate 5 of the superconducting wire and the plate-like metal terminal by the connecting plate 9 made of a highly conductive metal at at least one end of the superconducting wire 2. can do. When both ends of the superconducting wire 2 are connected to the metal substrate 5 of the superconducting wire by the connection plate 9 made of a highly conductive metal, the metal substrate is used when an abnormality such as quenching or thermal runaway occurs. It is preferable because current can be commutated to the material 5.
On the other hand, the connection structure at the end portion of the superconducting wire shown in FIG. 2B has a superconducting layer 7 via a conductive metal layer 8 from a plate-like metal terminal 4 via a connection plate 9 made of a highly conductive metal. The current flows through Therefore, in the structure of FIG. 2B, it is necessary to connect the conductive metal layer 8 and the metal base 5 using the connection plate 9 made of a highly conductive metal at both ends of the superconducting wire. . In this case, when an abnormality such as quenching or thermal runaway occurs, current is diverted to the metal base 5 via the connection plate 9 made of a highly conductive metal at both ends of the superconducting wire.

  2 (a) and 2 (b), in FIG. 2 (a), the metal substrate of the superconducting wire is formed by a connecting plate 9 made of a highly conductive metal at one end of the superconducting wire. It is preferable because the potential of the metal base 5 can be fixed only by connecting the material 5 and the plate-like metal terminal 4 and the superconducting wire 2 and the plate-like metal terminal 4 can be easily joined.

  Thus, according to this embodiment, the potential of the metal substrate can be fixed by electrically connecting the superconducting layer of the superconducting wire and the metal substrate at at least one end of the superconducting wire. In addition, it is possible to provide a superconducting device with improved stability without risk of dielectric breakdown. In addition, by electrically connecting the superconducting layer and the metal substrate at both ends of the superconducting wire, when a quench or thermal runaway occurs, the superconducting layer is connected via a connection plate made of a highly conductive metal. A current can be shunted to the metal substrate, and a superconducting device with improved stability can be provided.

  Next, a second embodiment of the present invention will be described. FIG. 3 is a diagram schematically showing a main configuration of a superconducting device according to the second embodiment of the present invention. FIG. 4 is a diagram showing superconductivity at both ends of the superconducting wire surrounded by a broken line in FIG. It is expanded sectional drawing of the part to which the wire and the plate-shaped metal terminal were connected. FIG. 4A and FIG. 4B each show a connected portion (connection structure) at one of the ends of the superconducting wire.

  In this embodiment, FIG. 4A shows that the conductive metal layer 8 of the superconducting wire 2 is integrally connected to a part of the plate-like metal terminal 4 and the plate-like metal substrate 5 is a highly conductive metal. The connection plate 9 is connected to the plate-like metal terminal 4. FIG. 4B shows that the conductive metal layer 8 of the superconducting wire 2 is integrally connected to a part of the plate-like metal terminal 4, but there is no connection plate 9 made of a highly conductive metal, and a metal substrate. 5 is not connected to the plate-like metal terminal 4 by the connection plate 9 made of a highly conductive metal.

  The connection structure of the superconducting wire 2 shown in FIGS. 4A and 4B can detect the normal conducting resistance when a normal conducting resistance is generated in the superconducting layer 7 of the superconducting wire 2 due to quenching, for example. It is a possible structure. Hereinafter, the principle of detecting the occurrence of normal conducting resistance will be described.

First, at one end of the superconducting wire 2 (FIG. 4B), there is a connection plate 9 made of a highly conductive metal that connects the plate-like metal terminal 4 and the metal substrate 5 of the superconducting wire 2. Absent. The voltage between both ends of the metal substrate 5, that is, the voltage between the metal substrate 5 at the end of the superconducting wire 2 in FIG. 4A and the metal substrate 5 at the end of the superconducting wire 2 in FIG. Assuming that V ₁ is the voltage across the superconducting layer 7 of the superconducting wire ₂ and V ₂ is the voltage across the metal substrate 5 (V ₁ ), only the inductance component of the superconducting coil appears. On the other hand, the normal voltage (V ₂ ) of the superconducting wire 7 does not show the resistance component of the superconducting coil and shows only the inductance component when it is normal, but if resistance occurs in the superconducting wire 7 due to quenching or the like, A vector sum of an inductance component and a resistance component having the same value as the both-end voltage (V ₁ ) appears. Therefore, when the difference value (V ₂ −V ₁ ) between these voltages is measured, the inductance component is canceled out, and the value of only the resistance component (the value of only the resistance component of the superconducting wire 7) can be extracted. This value is almost zero when normal. However, once a normal conducting resistance is generated in the superconducting layer 7, the voltage across the superconducting wire 7 (V ₂ ) also shows a resistance component vector in addition to the inductance component of the superconducting coil. Therefore, since the voltage difference value (V ₂ −V ₁ ) shows a positive value, it can be seen that an abnormality has occurred in the superconducting layer 7.
Further, the voltage (V ₃ ) between the conductive metal layer 8 and the metal base 5 shown in FIG. 4B or the voltage (V ₄ ) between the plate-like metal terminal 4 and the metal base 5 is shown. It can be seen that resistance was similarly generated in the superconducting layer 7 by measurement.

  In addition, the superconducting wire 2 in this embodiment may be a single wire as in the first embodiment of the present invention, or may be connected in the middle.

  Thus, according to this embodiment, the potential of the metal substrate can be fixed, and in addition to the improvement in stability with a low risk of dielectric breakdown, the occurrence of normal conductive resistance can be detected with high sensitivity.

  Next, a third embodiment of the present invention will be described. FIG. 5 is a diagram schematically showing a main configuration of a superconducting device according to the third embodiment of the present invention, and FIG. 6 is a connection plate made of a highly conductive metal surrounded by a broken line in FIG. It is sectional drawing to which the superconducting layer of the superconducting wire and the part to which the metal base material was connected was expanded.

  Of the superconducting wire 2 formed by sequentially laminating the metal base material 5, the intermediate layer 6, the superconducting layer 7 and the conductive metal layer 8, the metal base material 5 and the superconducting layer existing via the insulating intermediate layer 6. 7 are electrically connected to each other at a predetermined position in the longitudinal direction of the superconducting wire 2 by a connection plate 10 made of a highly conductive metal. This electrical connection can be made through the conductive metal layer 8. The connection between the metal base 5 and the connection plate 10 made of a highly conductive metal and the connection between the conductive metal layer 8 and the connection plate 10 made of a highly conductive metal connect flat surfaces to each other.

As a material of the connection plate 10 made of a highly conductive metal, a metal material that can electrically connect the metal substrate 5 of the superconducting wire 2 and the superconducting layer 7 can be used. Specifically, silver, copper, etc. are mentioned. Further, the connection plate (connection part) 10 made of a highly conductive metal electrically connects the metal substrate 5 of the superconducting wire 2 and the superconducting layer 7, and the current connected to the superconducting layer 7 when a quench occurs. Any shape can be used as long as the shape can be quickly commutated to the metal substrate 5. For example, a cross-sectional shape as shown in FIG. 6 having a U shape or a rectangular shape having a hollow inside can be used.
For the electrical connection by the connection plate 10 made of this highly conductive metal, a method that can electrically connect the metal substrate 5 and the superconducting layer 7 can be used. For example, the metal base 5 and the conductive metal layer 8 can be electrically connected by bringing them into contact with the connection plate 10 made of a highly conductive metal. Further, for example, electrical connection can be made using soldering, diffusion bonding, or the like.

  The electrical connection by the connecting plate 10 made of a highly conductive metal can fix the potential of the metal substrate 5 as long as it is at least one place in the longitudinal direction of the superconducting wire 2. By doing so, for example, when a quench occurs, current can be commutated from the superconducting layer 7 to the metal substrate 5. The more the number of connection points, the faster the current can be commutated from the superconducting layer 7 to the metal substrate 5. In addition, the electrical connection between the superconducting layer 7 and the metal substrate 5 by the connection plate 10 made of a highly conductive metal in this embodiment is made by the connection plate 9 made of a highly conductive metal at the end of the superconducting wire 2. When combined with the electrical connection between the metal substrate 5 and the conductive metal layer 8 of the superconducting wire 2, the current is commutated more rapidly from the superconducting layer 7 to the metal substrate 5 when, for example, a quench occurs. be able to.

  In addition, the superconducting wire 2 in this embodiment may be a single wire as in the first embodiment of the present invention, or may be connected in the middle.

  As described above, according to this embodiment, the potential of the metal substrate 5 can be fixed by connection at one or more locations in the longitudinal direction of the superconducting wire 2, and the current can be supplied to the superconducting layer by connection at two or more locations. 7 to the metal substrate 5. In addition, the current can be transferred from the superconducting layer 7 to the metal substrate 5 more rapidly as the number of connection points increases.

  In addition, examples of the use of the superconducting device according to the embodiment of the present invention include a superconducting generator, a superconducting power storage (SMES), a superconducting current limiter, a superconducting transformer, and a superconducting cable. In particular, the superconducting device according to the embodiment of the present invention can fix the potential of the metal substrate, and in addition to the conductive metal layer from the superconducting layer in the event of an abnormality such as a current quench, the current is commutated to the metal substrate side. Therefore, it can be suitably used for a superconducting fault current limiter.

It is a figure which shows typically the principal part structure of the superconducting apparatus which concerns on the 1st Embodiment of this invention. FIG. 2 is an enlarged cross-sectional view of a portion surrounded by a broken line in FIG. 1 where a superconducting wire and a plate-like metal terminal are connected. It is a figure which shows typically the principal part structure of the superconducting apparatus which concerns on the 2nd Embodiment of this invention. FIG. 4 is an enlarged cross-sectional view of a portion surrounded by a broken line in FIG. 3 where a superconducting wire and a plate-like metal terminal are connected. It is a figure which shows typically the principal part structure of the superconducting apparatus which concerns on the 3rd Embodiment of this invention. FIG. 6 is an enlarged cross-sectional view of a portion where a superconducting layer of a superconducting wire and a metal substrate are connected by a connection plate made of a highly conductive metal and surrounded by a dashed ellipse in FIG. 5.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Superconducting device, 2 ... Superconducting wire, 3 ... Winding frame, 4 ... Plate-shaped metal terminal, 5 ... Metal base material, 6 ... Intermediate layer, 7 ... Superconducting layer, 8 ... Conductive metal layer, 9, 10 ... Good Connection plate made of conductive metal

Claims (2)

A superconducting wire formed by sequentially laminating a superconducting layer and a conductive metal layer through an insulating intermediate layer electrically insulating on one side of a metal substrate;
At least one end portion of the superconducting wire has a connecting portion made of a silver or copper good-electricity metal that electrically connects the metal base of the superconducting wire and the conductive metal layer ,
The connection portion is integrally connected with one end overlapped with the surface of the superconducting wire opposite to the metal base or the intermediate layer of the conductive metal layer and the other end overlapped with the surface of the plate-like metal terminal. superconducting and wherein the that. 2. A connection plate made of a highly conductive metal of silver or copper that electrically connects the metal base and the conductive metal layer at at least one location in the longitudinal direction of the superconducting wire. Superconducting equipment.

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