JP2004335160A - Current leads for superconducting devices - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a stably operable current lead in which degradation of conductive capacity and local heating can be evaded even if it is installed in the vicinity of a superconductive coil. <P>SOLUTION: In the current lead 1 consisting of a room-temperature side lead 7 using a conductive metal material and a low-temperature side lead 8 using a parallel connection body of a plurality of unit conductors 4 made of tape-shaped oxide superconductive wires, the plurality of unit conductors 4 are buried in grooves of a support member 5 with their wide faces directed in the same direction to make up a low-temperature side current path, and the unit conductors 4 are arranged so as to receive a generated magnetic field of the superconductive coil 2 in parallel with the wide faces and are to be connected to the superconductive coil 2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a superconducting coil for storing superconducting energy, a superconducting current limiter, a superconducting cable, a superconducting generator, a superconducting transformer, and the like, in which power is supplied from a room temperature power supply to a cryogenically cooled superconducting device. Current lead.
[0002]
[Prior art]
Superconducting coils are used in physical property research equipment, magnetic resonance equipment, and the like, and are also being applied to magnetic levitation trains, magnetic confinement equipment for nuclear fusion, and the like. However, since the superconducting coil is used in a cryogenic temperature and is operated by supplying power from a power source placed at room temperature, heat entering the cryogenic region through a current lead for supplying power is suppressed. Is an important issue. That is, liquid helium, which is often used as a refrigerant, is an expensive liquid for which the price of one liter is as high as about 1,000 yen, and is necessary for re-liquefying liquid helium evaporated by the invasion heat of 1 W by a refrigerator. The refrigerator input reaches about 400 W even under ideal conditions, and actually reaches about 1000 W. Therefore, if there is a large amount of heat penetrating through the current lead, not only does the cost associated with the purchase of liquid helium, etc. rise, but also the refrigerator used for reliquefaction becomes large-sized and large-capacity. In order to realize certain miniaturization and low power consumption, it is important to reduce the heat penetration of the current leads.
[0003]
For this reason, in the development of various superconducting devices, the development of current leads with low heat penetration has been promoted as a factor in determining the possibility of their practical application.With the discovery of a so-called high-temperature superconducting material, this was transferred to the current path on the low-temperature side. High temperature superconducting current leads used have been developed.
FIG. 2 is a longitudinal sectional view of a conventional superconducting magnet device using a high-temperature superconducting current lead. The superconducting coil 2 is housed inside the cryogenic vessel 3 and is cooled by a coolant such as liquid helium (not shown). The superconducting coil 2 incorporates a pair of current leads 1 for supplying power from a power source (not shown) disposed at a room temperature portion. The current lead 1 is a so-called high-temperature superconducting current lead, and is formed by a series connection of a room-temperature-side lead 7 using a good conductive metal material as a current path and a low-temperature side lead 8 using a high-temperature superconducting material as a current path. . FIG. 3 is a sectional view taken along line YY of the current lead 1 incorporated in FIG. 2, that is, a sectional view of a low-temperature side lead 8 using a high-temperature superconducting material as a current path (for example, see Patent Document 1 or Patent Document 2). reference). As shown in FIG. 3, the low-temperature side lead 8 is composed of a plurality of unit conductors 4A made of a silver-sheathed tape-shaped high-temperature superconducting wire, and a wide surface formed on the surface of a cylindrical support member 6 in a circumferential direction of a cylindrical coordinate system. It is arranged so as to be in parallel with. The critical current value of the tape-shaped high-temperature superconducting wire used as the unit conductor 4A is affected by a magnetic field. Particularly, when a magnetic field is applied in a direction perpendicular to a wide surface, the critical current value is significantly reduced. For this reason, by arranging the unit conductors 4A as described above, the direction of the self-magnetic field generated in the current lead 1 is made parallel to the wide surface, and the magnetic field component in the vertical direction is reduced to suppress a decrease in the critical current value. . Note that a copper lead formed by bundling a plurality of copper wires made of a good conductive metal material is often used as the room temperature side lead 7.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. Hei 10-188691 [Patent Document 2]
JP-A-11-260162
[Problems to be solved by the invention]
As described above, in the conventional high-temperature superconducting current lead, a plurality of tape-shaped high-temperature superconducting wires are arranged on the surface of the cylindrical support member such that the wide surface is parallel to the circumferential direction of the cylindrical coordinate system, and the low-temperature side lead is disposed. With this configuration, a decrease in the critical current value due to the self-magnetic field is suppressed. However, even in the high-temperature superconducting current lead configured as described above, if it is used by being connected to the superconducting coil 2 as shown in FIG. 2, for example, there is a risk that a malfunction may occur due to the influence of the magnetic field generated by the superconducting coil 2. . That is, in the superconducting coil 2 as shown in FIG. 2, a magnetic field is generated inside the coil, for example, in the upward direction in the figure, and a magnetic field in the opposite direction, for example, downward in the figure, is generated outside the coil. A radial magnetic field is generated at the upper and lower ends of the coil winding. Accordingly, a magnetic field from the superconducting coil 2 as shown by a thin line with an arrow in FIG. 3 is applied to the low-temperature side lead 8 of the current lead 1 arranged as shown in FIG. For this reason, the tape-shaped high-temperature superconducting wire of the unit conductor 4A arranged in the vicinity (region A) of the region indicated by A in FIG. 3 receives the magnetic field from the superconducting coil 2 in parallel to the wide surface, and 2B, the tape-shaped high-temperature superconducting wire of the unit conductor 4A disposed in the vicinity (region B) of the unit conductor receives the magnetic field from the superconducting coil 2 vertically. As described above, in a tape-shaped high-temperature superconducting wire, when a magnetic field is applied in a direction perpendicular to the wide surface, the critical current value is significantly reduced. Therefore, the unit conductor 4A in the region A is affected by the magnetic field from the superconducting coil 2. However, the critical current value of the unit conductor 4A in the region B is significantly reduced due to the magnetic field from the superconducting coil 2. For this reason, a large current flows through the unit conductor 4A in the region A, and a small current flows through the unit conductor 4A in the region B. If such a drift occurs, not only does the current carrying capacity of the current lead decrease, but also the heat generated by the connection resistance of the connection with the room-temperature-side lead 7 varies, which may cause local heating. .
[0006]
The present invention has been made in consideration of the problems of the related art as described above, and a low-temperature side lead configured using a plurality of unit conductors made of a tape-like high-temperature superconducting wire is installed near a superconducting coil. Also, it is an object of the present invention to provide a current lead for a superconducting device that can stably operate by preventing the occurrence of a drift between a plurality of unit conductors, avoiding a decrease in current carrying capacity and avoiding local heating due to connection resistance.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention,
A current lead for a superconducting device that supplies power from a power supply at room temperature to a superconducting device cooled to cryogenic temperature. It consists of a series connection of a room temperature side current path and a low temperature side current path. In a current lead for a superconducting device, which is constituted by a metal material, and a low-temperature side current path is constituted by a parallel connection body of a plurality of unit conductors formed of a tape-shaped oxide superconducting wire,
(1) The tape-shaped oxide superconducting wires of the plurality of unit conductors are arranged with their wide surfaces facing in the same direction,
(2) In a current lead for a superconducting device for supplying power to a superconducting coil, a tape-shaped oxide superconducting wire of a plurality of unit conductors is arranged such that a wide surface thereof substantially coincides with a radial direction of the superconducting coil. It shall be incorporated.
[0008]
(3) In the above (1) and (2), a plurality of unit conductors constituting a low-temperature side current path are embedded in a groove provided in a support member made of a low heat conductive metal material. ,further,
(4) The unit conductor is connected to the groove of the support member having the metal thin film formed on the outer surface by soldering via the metal thin film.
If the current lead is configured as in the above (1), the wide surface of the tape-shaped oxide superconducting wire of the unit conductor is arranged and incorporated so as to be parallel to the magnetic field generated by the superconducting device, so that the magnetic field generated by the superconducting device is reduced. The reduction in the critical current of the tape-shaped oxide superconducting wire is suppressed, and the current flows evenly through each unit conductor without causing drift between the unit conductors. For example, in a current lead for a superconducting device that supplies power to a superconducting coil, by arranging and incorporating as described in (2) above, a decrease in the critical current of the tape-shaped oxide superconducting wire is suppressed, and a drift occurs. Therefore, current flows evenly through each unit conductor.
[0009]
If the unit conductor is buried in the groove of the support member as described in (3) above, the electromagnetic force acting due to the interaction with the magnetic field is stably supported, and the tape-shaped oxide superconducting wire is inadvertently generated by some factor. Even if a quench (normal conduction transition) occurs, the current is bypassed to the support member to avoid damage. Since the support member is made of a low thermal conductive metal material, the amount of heat penetrating through the support member can be suppressed to a small amount. In particular, according to the above (4), even when the support member is formed of a metal material such as stainless steel or titanium which is difficult to be soldered, the unit conductor and the support member can be electrically connected to each other. Since mechanically strong bonding can be performed, the electromagnetic force is supported and the current bypass at the time of quench is performed stably.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to examples. The present invention is not limited to this embodiment, but is widely applied to configurations based on the same basic philosophy.
1A and 1B are configuration diagrams of an embodiment of the present invention, in which FIG. 1A is a longitudinal sectional view of a superconducting magnet device incorporating a current lead for a superconducting device of the present invention, and FIG. It is sectional drawing of the XX plane of the low-temperature side current path of the current lead for superconducting devices which was used. As shown in FIG. 1A, in the present superconducting magnet device, a superconducting coil 2 is housed inside a cryogenic vessel 3, and a current lead 1 for supplying power to the superconducting coil 2 from a power source (not shown) is incorporated. Have been. The current lead 1 is a series connection of a room-temperature-side lead 7 whose current path is made of a good conductive metal material and a low-temperature side lead 8 whose current path is made of a unit conductor 4 made of a tape-shaped oxide superconducting wire. It is configured as Among them, the low-temperature side lead 8 has a unit conductor 4 composed of a plurality of silver-sheathed tape-shaped oxide superconducting wires in a groove of a support member 5 made of a stainless material, as shown in FIG. The low-temperature side lead 8 of this configuration is buried and connected by soldering. A feature of the low-temperature side lead 8 is that a plurality of unit conductors 4 are arranged with their wide surfaces facing in the same direction. The superconducting magnet device shown in FIG. 1A is characterized in that the current lead 1 is arranged such that the wide surface of the unit conductor 4 of the low-temperature side lead 8 substantially matches the radial direction of the superconducting coil 2. It is built in.
[0011]
Therefore, in the present device, the low-temperature side lead 8 of the current lead 1 is arranged close to the superconducting coil 2, but the direction of the magnetic field generated by the superconducting coil 2 is different from the wide surface of the unit conductor 4 of the low-temperature side lead 8. Since the directions are parallel to each other, a decrease in the critical current of the tape-shaped oxide superconducting wire of the unit conductor 4 can be suppressed to a small extent. Further, since the strengths of the magnetic fields applied to the plurality of unit conductors 4 are substantially the same, current flows almost uniformly in each unit conductor 4 and there is no possibility that a drift occurs. Therefore, it must be used stably without causing a decrease in current carrying capacity or local heating caused by the current flowing between the unit conductors of the low-temperature side lead due to an external magnetic field, as seen in conventional current leads. Can be.
[0012]
The support member 5 in which the unit conductor 4 of the low-temperature side lead 8 is embedded serves to support a force applied to the unit conductor 4 such as an electromagnetic force. Therefore, when the unit conductor 4 is made of a highly rigid stainless steel material, it is effectively supported. In particular, when the unit conductor 4 is embedded in the groove as shown in FIG. In addition, since the stainless steel material is a material having low thermal conductivity, heat entering through the support member can be suppressed to a very small level.
When the tape-shaped oxide superconducting wire of the unit conductor 4 is quenched for some reason, the support member 5 has a role of bypassing an electric current to ensure safety. For this reason, in the configuration of the present embodiment, the unit conductor 4 composed of a silver-sheathed tape-shaped oxide superconducting wire and the supporting member 5 are connected by soldering and are electrically well bonded. When using a support member 5 made of a material that is difficult to directly solder, such as a stainless steel material or a metal material such as titanium, a thin film of copper or a copper alloy is formed on the bonding surface in advance, By forming the thin film surface and the unit conductor 4 by soldering, strong adhesion can be obtained.
[0013]
【The invention's effect】
As described above, according to the present invention,
A current lead for a superconducting device that supplies power from a power supply at room temperature to a superconducting device cooled to cryogenic temperature,
(1) Since it is configured as described in claim 1, the wide surface of the tape-shaped oxide superconducting wire of the unit conductor constituting the low-temperature side lead is arranged so as to be parallel to the magnetic field generated by the superconducting device. By incorporating, the reduction of the critical current of the tape-shaped oxide superconducting wire due to the magnetic field generated by the superconducting device is suppressed, so that the occurrence of drift between the plurality of unit conductors is prevented, and the reduction of the current carrying capacity and connection Local heating due to resistance is avoided, and a current lead for a superconducting device that can operate stably can be obtained.
[0014]
(2) According to the second aspect, a current lead for a superconducting device particularly suitable for a superconducting device using a superconducting coil can be obtained.
(3) Further, according to the present invention, the electromagnetic force applied to the unit conductor constituting the low-temperature side lead is stably supported, and even if the tape-shaped oxide superconducting wire is quenched by some factor. In addition, since the current is bypassed to the support member to avoid breakage, local heating due to a reduction in current carrying capacity and connection resistance is avoided, and the current lead is suitable for a superconducting device that can operate stably.
(4) Further, according to the present invention, the unit conductor and the support member are strongly joined electrically and mechanically, and the support of the electromagnetic force and the current bypass at the time of quench are performed stably. In addition, the present invention is more suitable as a current lead for a superconducting device that can be operated stably while avoiding a decrease in current-carrying capacity and local heating due to connection resistance.
[Brief description of the drawings]
1A is a longitudinal sectional view of a superconducting magnet device incorporating a current lead for a superconducting device of the present invention, and FIG. 1B is a low-temperature side current of the current lead for a superconducting device shown in FIG. FIG. 2 is a longitudinal sectional view of a superconducting magnet device using a conventional high-temperature superconducting current lead. FIG. 3 is a sectional view of a current lead incorporated in FIG. [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Current lead 2 Superconducting coil 3 Cryogenic container 4 Unit conductor 5 Support member 7 Room temperature side lead 8 Low temperature side lead

Claims (4)

A current lead for a superconducting device that supplies power from a power supply at room temperature to a superconducting device cooled to cryogenic temperature. It consists of a series connection of a room temperature side current path and a low temperature side current path. In a current lead for a superconducting device, which is constituted by a metal material, and a low-temperature side current path is constituted by a parallel connection body of a plurality of unit conductors formed of a tape-shaped oxide superconducting wire,
A current lead for a superconducting device, wherein a plurality of tape-shaped oxide superconducting wires of unit conductors are arranged with their wide faces facing in the same direction. A superconducting device current lead for supplying power to the superconducting coil, in which tape-shaped oxide superconducting wires of a plurality of unit conductors are arranged and arranged such that the wide surface thereof substantially coincides with the radial direction of the solenoid type superconducting coil. The current lead for a superconducting device according to claim 1, wherein the current lead is provided. 3. The superconducting device according to claim 1, wherein a plurality of unit conductors constituting a low-temperature side current path are buried in a groove provided in a support member made of a low thermal conductive metal material. Current lead. The current lead for a superconducting device according to claim 3, wherein the unit conductor is soldered and connected via a metal thin film in a groove of a support member having a metal thin film formed on an outer surface.

Images