JP2000101153A - Current lead for superconducting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current lead which is tolerant of thermal shrinkage and electromagnetic force without increase in heat penetration. SOLUTION: In a low temperature-side part of this current lead, a support 302 is provided with a channel. A sheath type high-temperature superconductor 300 is inserted in layers in the channel. Then, the support 302 and the sheath type high-temperature superconductor 300 are fastened into one body by an insulating tape 400. Both ends of the sheath type high-temperature superconductor 300 are connected electrically and mechanically to a low-temperature terminal 304 and a high-temperature terminal 303 respectively by solder 500. The low-temperature terminal 304 and the high-temperature terminal 303 are formed at copper or a copper alloy. The support 302 is formed of the material of a low coefficient of thermal conductivity. The insulating tape is constituted of an aramid fiber insulating sheet of high strength and an insulating sheet of a low coefficient of friction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting apparatus such as a magnetic levitation train, a magnetic resonance imaging apparatus, etc., for supplying a current from an external power supply to a superconducting coil or the like which is housed in a vacuum insulated container and immersed in liquid helium. And a current lead for a superconducting device.

[0002]

2. Description of the Related Art Since a superconducting coil of a superconducting device maintains a superconducting state by being cooled by a cryogenic refrigerant such as liquid helium, it is usually provided with a radiation shield using cryogenic nitrogen and multiple heat insulating layers. It is stored in a vacuum insulated container while immersed in liquid helium. In order to excite the superconducting coil, a current lead is incorporated in a vacuum insulated container and connected to an external power supply to supply an exciting current. At this time, since the normal temperature part and the extremely low temperature part will be connected,
If much heat enters the cryogenic part through the current lead, a large amount of expensive liquid helium will be consumed.
Therefore, the current lead is self-cooled by using the low-temperature helium gas vaporized by heat penetration by itself, minimizing the heat penetration due to conduction from the normal temperature side and the Joule heat generated by energization entering the cryogenic part as much as possible. It is configured with consideration for. It is effective to reduce the cross-sectional area of the conductor of the current lead in order to suppress heat intrusion from the room temperature part.However, if the cross-sectional area of the conductor is reduced, the electric resistance of the current lead increases, so that Joule heat increases. Become.
Therefore, it is important that these components be balanced in consideration of the cooling effect.

[0003] In general, a good conductor such as copper or a copper alloy has been used as a conductor of a current lead. However, since the discovery of a high-temperature superconductor, the high-temperature superconductor has been in a superconducting state even at the temperature of liquid nitrogen. Therefore, since it does not generate Joule heat and has lower thermal conductivity than a copper conductor, it is expected to be used as a conductor of a low-temperature side lead portion of a current lead. For this reason, a current lead for a superconducting device capable of reducing heat penetration into a cryogenic portion has been developed, and is proposed in, for example, Japanese Patent Application Laid-Open No. 4-168705. In this proposal, a current lead is constituted by a plurality of parallelly arranged oxide superconducting wires, and the oxide superconducting wires are formed by covering an oxide superconducting conductor with a metal sheath. Further, the plurality of superconducting wires arranged in parallel are integrated into a conductor by diffusion bonding. Further, Japanese Patent Application Laid-Open No.
In Japanese Patent No. 09530, a plurality of types of current leads having different superconducting characteristics, for example, a low-temperature portion, a medium-temperature portion, and a high-temperature portion, are connected in the longitudinal direction by connecting members.

[0004] The current technology makes it possible to suppress the heat conduction of a sheath-type high-temperature superconducting conductor to be smaller than that of pure silver by alloying the sheath material (for example, adding gold). In addition, compared to the bulk type high-temperature superconducting conductor, the sheath-type high-temperature superconducting conductor transfers current to the sheath material (silver or silver alloy) when a quench occurs in the conductor (transition from the superconducting state to the normal conducting state). Because it flows by bypass,
Because of its high safety, it is expected that large capacity current leads will be applied to low temperature side leads. At present, there is a development example of a 10 kA class superconducting current lead. Therefore, in order to realize economical operation of the superconducting device, the development of a current lead using a high-temperature superconducting conductor has been activated.

Next, a specific drawing will be described. FIG.
It is the schematic which shows an example of the superconducting device using the current lead for superconducting devices by a prior art, (a) is a whole block diagram,
(B) is an enlarged sectional view of a BB 'part of (a), and (c) is an enlarged sectional view of a CC' part of (a). 4, 1 is a superconducting coil, 2 is a current lead, 3 is a vacuum container, 4 is liquid helium, 10 is a liquid helium container, 11
Is a lead lead, 20 is an intermediate connection fitting, 21 is a low temperature terminal, 22 is a low temperature side lead, 23 is a high temperature side lead, 24 is a normal temperature terminal, 41 is helium gas, 221 is a cylindrical container,
22 is a high-temperature superconducting conductor, 223 is a hollow portion, 231 is a cylindrical container, 232 is a conductor bundle, 233 is a hollow portion, 241 is an outlet tube, and 242 is a terminal fitting. The current lead 2 includes a low-temperature terminal 21, a low-temperature lead 22, a high-temperature lead 23, and a normal-temperature terminal 24 from below, and the low-temperature lead 22 and the high-temperature lead 23 are electrically and mechanically connected by an intermediate fitting 20. ing. The low-temperature terminal 21 is connected to the lead 11
Is connected to the superconducting coil 1 immersed in the liquid helium 4 stored in the liquid helium container 10 insulated by vacuum. The room temperature terminal 24 is in the atmosphere outside the vacuum vessel 3 showing only a part thereof, and is connected to an external power supply (not shown) via a terminal fitting 242. The helium gas 41 flows into the inside of the current lead 2 from the flow hole provided in the low-temperature terminal 21, cools the conductor inside the current lead 2, and is discharged outside through the outlet tube 241 provided in the room temperature terminal 24. , And may be recovered. The low-temperature side lead 22 includes a cylindrical container 221 and a high-temperature superconducting conductor 222 disposed inside the cylindrical container 221, and has a hollow portion 223 between them. This hollow portion 223 is filled with helium gas 41
Flows, high-temperature superconducting conductor 222 is maintained in a superconducting state. In the drawing, the high-temperature superconducting conductor 222 is shown as a flat sheath. The high-temperature side lead 23 includes a cylindrical container 231 and a conductor bundle 23 passing therethrough.
The helium gas 41 for cooling the conductor flows through the hollow portion 233.

FIGS. 5A and 5B are conceptual diagrams showing a low-temperature side lead of a current lead for a superconducting device according to the prior art. FIG. 5A is a conceptual diagram of a conductor portion, and FIG. 5B is a conceptual diagram showing a conductor configuration of a low-temperature side lead. is there. As shown in (a), in the conductor portion, the sheath-type high-temperature superconductors 240 to 243 are gradually shortened in this order, and these sheath-type high-temperature superconductors 240 to 243 are formed.
Are arranged in parallel so that the high-temperature side end faces thereof are aligned, and the number of laminated sheath-type high-temperature superconducting conductors decreases as the temperature decreases. In addition, the sheath-type high-temperature superconducting conductors 240 to 243 are integrated by diffusion bonding between adjacent metal sheaths. Further, as shown in FIG. 5B, a groove provided in a support 200 made of a material having low thermal conductivity is provided in FIG.
The sheath-type high-temperature superconductors 240 to 243 shown in (a) are inserted and fixed using a resin 250.

[0007]

In the low-temperature side lead having the above-described structure, when cooled, the difference in thermal shrinkage between the support 200, the sheath-type high-temperature superconducting conductors 240 to 243, and the resin 250 causes the difference. In this case, cracks may occur in the resin 250. Further, in order to maintain high strength, it is possible to solve the problem by enlarging the cross section of the resin portion. However, heat penetration into the cryogenic portion increases due to heat conduction of the resin portion.

An object of the present invention is to provide a current lead for a superconducting device which can withstand heat shrinkage and electromagnetic force without increasing the amount of heat penetration.

[0009]

According to the present invention, a current is supplied from an external power supply to a superconducting coil housed in a vacuum insulated container and cooled to a very low temperature by liquid helium. In a current lead for a superconducting device in which a high-temperature side lead made of a good conductive metal and a low-temperature side lead made of a sheath-type high-temperature superconducting conductor are connected in series, the groove formed in the support of the low-temperature side lead is The sheath-type high-temperature superconducting conductor is laminated and arranged, and the support and the sheath-type high-temperature superconducting conductor are integrated using an insulating tape.

Further, the insulating tape used above is an insulating tape comprising an insulating sheet having a low coefficient of friction and an insulating sheet made of aramid fiber.

[0011]

1 is a conceptual diagram showing an example of a conductor configuration of a low-temperature side lead of a current lead for a superconducting device according to the present invention. FIG. 1A is a cross-sectional view, and FIG. It is a perspective view of the part on the right side from A 'plane. In FIG. 1, the support 30
2 is provided with a groove, into which the sheath-type high-temperature superconducting conductor 300 is laminated and inserted, and the support 302 and the sheath-type high-temperature superconducting conductor 300 are integrally fixed by the insulating tape 400. Further, both ends of the sheath-type high-temperature superconducting conductor 300 are connected to the low-temperature terminal 304 and the high-temperature terminal 30 respectively.
3 is electrically and mechanically connected by a solder 500. The low-temperature terminal 304 and the high-temperature terminal 303 are made of copper or a copper alloy. The support 302 is made of a material having low thermal conductivity, for example, stainless steel or glass fiber reinforced resin.

FIG. 2 is a conceptual diagram showing a configuration example of the insulating tape 400 of FIG. The insulating tape 400 includes an insulating sheet 401 made of high-strength aramid fiber and an insulating sheet 402 having a low friction coefficient. The insulating sheet 40
Aramid fiber is used as the material 1 because of its high tensile strength even at extremely low temperatures. As the insulating sheet 402 having a low friction coefficient, for example, a sheet made of polytetrafluoroethylene can be used. In addition, by winding the insulating tape 400 so that the surface on the side of the insulating sheet 402 having a low coefficient of friction is in contact with the sheath-type high-temperature superconducting conductor 300 among the two surfaces of the insulating tape 400, Slip occurs at the contact portion between the core 400 and the sheath-type high-temperature superconducting conductor 300, and no distortion occurs in the sheath-type high-temperature superconducting conductor 300 due to the difference in thermal shrinkage of each member. Deterioration is suppressed, and the structure is resistant to heat shrinkage.

In the configuration example of the insulating tape 400 shown in FIG. 2, the insulating tape 400 is wound so that the surface on the side of the insulating sheet 402 having a low friction coefficient abuts on the sheath-type high-temperature superconducting conductor 300. In addition, even if the relative positions of the low friction coefficient insulating sheet 402 and the aramid fiber insulating sheet 401 in the sheet width direction are slightly shifted, the surface of the aramid fiber insulating sheet 401 is not covered by the sheath-type high-temperature superconducting conductor 30.
The width of the insulating sheet 402 having a low coefficient of friction is made larger than the width of the insulating sheet 401 made of aramid fiber so as not to come into contact with zero.

FIG. 3 is a conceptual diagram showing a different conductor configuration example of the low-temperature side lead of the current lead for a superconducting device according to the present invention, and is a partial side view of the low-temperature side lead portion. In the conductor configuration example of FIG. 3, similarly to the conductor configuration example of FIG. 1, the sheath-type high-temperature superconducting conductor 300A is inserted into a groove provided in the support 302A, and the support 302A is insulated by the insulating tape 400.
1 and the sheath-type high-temperature superconducting conductor 300A are integrally fixed, but is different from the conductor configuration example of FIG. 1 in that the number of layers of the sheath-type superconducting conductor 300A decreases as the temperature decreases. In FIG. 3, the sheath-type high-temperature superconducting conductor 300 moves from the right high temperature side to the left low temperature side.
A configuration in which the number of stacked layers A is reduced is indicated by a broken line.
In order to enable the sheath-type high-temperature superconducting conductor 300A having such a configuration to be integrally fixed to the support 302A by the insulating tape 400, the sheath-type high-temperature superconducting conductor is located on the lower temperature side on the left side of FIG. 300
A, the upper surface of the support 302A and the sheath-type high-temperature
Slits 311 and 312 are provided with depths corresponding to the height differences d1 and d2 from the upper surface of 0A, and the wound insulating tape 400 is configured to abut the upper surface of the sheath-type high-temperature superconducting conductor 300A. I have.

In the example of the conductor configuration shown in FIG. 3, the configuration of the connection between the sheath-type high-temperature superconducting conductor 300A and the low-temperature terminal and the high-temperature terminal (not shown), the configuration of the insulating tape 400, the material of the support 302A, the low-temperature terminal and The material of the high-temperature terminal may be the same as the conductor configuration example of FIG. In the conductor configuration example shown in FIG. 1 or FIG. 3, as the insulating tape 400 is wound more densely, the fixing of the sheath-type high-temperature superconducting conductors 300, 300A to the supports 302, 302A becomes more sufficient. It becomes something. On the other hand, in the sheath type superconducting conductors 300 and 300A,
It is necessary that the cooling surface area by direct contact with the low-temperature helium gas be kept to a minimum. Therefore, the insulating tape 400 is wound at a pitch such that the necessary minimum cooling surface area of the sheath-type high-temperature superconducting conductors 300 and 300A is secured, and the fixing to the supports 302 and 302A is sufficient. It is good to do so.

[0016]

According to the present invention, by providing a conductor structure in which a sheath-type high-temperature superconducting conductor and a support are integrated using an insulating tape, it is possible to provide a conductor structure capable of withstanding heat shrinkage and electromagnetic force. it can. Further, since a resin for fixing the sheath-type high-temperature superconducting conductor to the support as in the conventional configuration is not used, it is possible to prevent an increase in the amount of heat entering the cryogenic portion. Furthermore, as insulating tape,
By using a composite insulating tape composed of an insulating sheet with a low coefficient of friction and a high-strength aramid fiber insulating sheet, slippage occurs at the contact between the insulating tape and the sheath-type high-temperature superconducting conductor during thermal contraction. Is generated, and the structure can withstand heat shrinkage.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an example of a conductor configuration of a low-temperature side lead of a current lead for a superconducting device according to the present invention.
(B) is a perspective view of a part on the right side of the AA 'plane of (a).

FIG. 2 is a conceptual diagram showing a configuration example of the insulating tape of FIG.

FIG. 3 is a conceptual diagram showing a different conductor configuration example of the low-temperature side lead of the current lead for a superconducting device of the present invention.

4A and 4B are conceptual diagrams showing an example of a superconducting device using a current lead for a superconducting device according to the related art, where FIG. 4A is an overall configuration diagram, and FIG. 4B is an enlarged cross-sectional view of a portion BB ′ of FIG. ,
(C) is an enlarged sectional view of a CC ′ portion of (a).

5A and 5B are conceptual diagrams showing a low-temperature side lead of a current lead for a superconducting device according to a conventional technique, wherein FIG.
(B) is a conceptual diagram showing a conductor configuration of a low-temperature side lead.

[Explanation of symbols]

300, 300A ... sheath type high-temperature superconducting conductor, 302,
302A: support, 303: high-temperature terminal, 304: low-temperature terminal, 311, 312: slit, 400: insulating tape,
Reference numeral 401 denotes an insulating sheet, 402 denotes an insulating sheet having a low coefficient of friction, and 500 denotes a solder.

Claims (2)

[Claims] An electric power is supplied from an external power supply to a superconducting coil housed in a vacuum insulated container and cooled to a very low temperature by liquid helium, wherein a high-temperature side lead made of a good conductive metal and a sheath-type high-temperature superconducting conductor are provided. In the current lead for superconducting devices, wherein the low-temperature side lead is connected in series, the sheath-type high-temperature superconducting conductor is laminated and arranged in a groove formed in a support of the low-temperature side lead, and A current lead for a superconducting device, wherein the sheath-type high-temperature superconducting conductor is integrated using an insulating tape. 2. The current lead for a superconducting device according to claim 1, wherein said insulating tape comprises an insulating sheet having a low friction coefficient and an insulating sheet made of aramid fiber.