JPH11297524A - Current leads for superconducting devices - Google Patents

Abstract

(57) [Summary] To provide a current lead for a superconducting device which can reduce the amount of heat entering a cryogenic part. A high-temperature superconductor is formed in a groove formed in a low-temperature terminal of a low-temperature side lead of a current lead for a superconducting device.
And one or several metal-based superconductors 60 from the coil terminals of the superconducting coil are inserted into the grooves or holes 61 formed on one or more surfaces of the low-temperature terminal 21 by soldering. It is installed so as to wrap in the axial direction and soldered.

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 immersed in liquid helium and housed in a vacuum insulated container. 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 a multilayer heat insulating layer. 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 the heat penetration by itself, minimizing the heat penetration due to conduction from the room 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 to provide a balanced configuration 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 in a liquid nitrogen temperature state. 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 part has been developed.

(Reference material: Current lead using ceramic high-temperature superconductor, Source: EMC (Electromagnetic Environment Engineering Information)
1994.7.5 (NO.75) P32-(1994)) The sheath-type high-temperature superconductor used in this reference material is made by alloying the sheath material (for example, by adding gold), and comparing it with the thermal conductivity of pure silver. It is possible with current technology to keep the thermal conductivity low. In addition, when a quench occurs in the conductor (transition from the superconducting state to the normal conducting state), the current in the sheath-type high-temperature superconductor is bypassed to the sheath material (silver or silver alloy) compared to the bulk-type superconductor. It is expected to be applied to low-temperature-side leads of large-capacity current leads because of high safety. At present, there is a development example of a 10 kA class superconducting current lead. For this reason, in order to realize economical operation of the superconducting device, the development of a current lead using a high-temperature superconductor has been activated.

FIG. 3 is a conceptual diagram showing an example of a superconducting device using a current lead for a superconducting device according to the prior art.
The drawing includes a partial sectional view of the current lead. In FIG. 3, 1 is a superconducting coil, 2 is a current lead, 3 is a vacuum vessel, 4 is liquid helium, 10 is a liquid helium vessel, 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 superconductor, 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 side lead 22 and the high-temperature side lead 23 are electrically and mechanically connected by the intermediate connection fitting 20. The low-temperature terminal 21 is connected to the superconducting coil 1 immersed in the liquid helium 4 contained in the liquid helium container 10 insulated by vacuum through the lead-out lead 11. 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 that has cooled the conductor of the current lead 2 is discharged to the outside through an outlet tube 241 provided at the room temperature terminal 24, or may be recovered in some cases. The low-temperature side lead 22 becomes the cylindrical container 221 and the high-temperature superconductor 222 arranged inside the cylindrical container 221,
There is a hollow part 223 between them. When the helium gas 41 flows through the hollow portion 223, the high-temperature superconductor 2
22 is maintained in a superconducting state. Helium gas 41 is
It flows into the inside of the current lead 2 from the flow hole provided in the low-temperature terminal 21. Generally, the high-temperature superconductor 222 may be a bulk type or a sheath type. Also, the shape is polygonal,
There are cylinders and cylinders. In the drawing, the high-temperature superconductor 222 is formed in a plate shape (sheath type). The high-temperature side lead 23 is composed of a cylindrical container 231 and a conductor bundle 232 passing therethrough, and the helium gas 41 for cooling the conductor flows through the hollow portion 233.

FIG. 4 is a detailed view of a low-temperature terminal of a current lead for a superconducting device according to the prior art. In FIG. 4, 30
Is a groove, 40 is a bolt hole, and other components are shown in FIG.
And the same reference numerals are used. The high-temperature superconductor 2 is inserted into the groove 30 formed in the low-temperature terminal 21 made of a copper conductor or the like.
22 are installed and electrically and mechanically connected by soldering. Further, the low-temperature terminal 21 is provided with a bolt hole 40 for connecting to a coil terminal of a superconducting coil (not shown).

FIG. 5 is a conceptual view of a connection portion of a low-temperature terminal of a current lead for a superconducting device according to the prior art. In FIG. 5, 1 is a superconducting coil, 50 is a coil terminal, 51 is a bolt hole, and other components are the same as those in FIG. The low-temperature terminal 21 and the coil terminal 50 are fixedly connected by a plurality of bolts (not shown). The current from the external power supply is
Electricity is supplied through the path of the intermediate connection fitting, the low-temperature side lead, the low-temperature terminal 21, the coil terminal 50, and the superconducting coil 1.

[0009]

In the conventional low-temperature terminal structure, a groove is formed in a low-temperature terminal made of a copper conductor, and a low-temperature-side lead conductor made of a sheath-type high-temperature superconductor is connected to this groove by soldering. The low-temperature terminal and the coil terminal of the superconducting coil are connected by screws or the like. Therefore, when a current flows, not only does the temperature rise due to Joule heat generation and heat generation due to contact resistance between terminals, but also in the case of a large-capacity type current lead, there is a problem that the amount of heat entering the cryogenic portion increases. .

An object of the present invention relates to a structure of a low-temperature terminal of a low-temperature side lead and a coil terminal of a superconducting coil, and to provide a current lead for a superconducting device capable of reducing the amount of heat entering a cryogenic part. It is in.

[0011]

In order to solve the above-mentioned problems, the present invention provides a method for supplying a current 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 copper or copper alloy conductor and a low-temperature side lead made of a high-temperature superconductor are connected in series, a high-temperature superconductor is inserted into a groove formed in a low-temperature terminal of the low-temperature side lead. Installed and soldered, and one or more metal-based superconductors from the coil terminals of the superconducting coil in the grooves or holes formed on one or more surfaces of the low-temperature terminal with the high-temperature superconductor. The structure is such that it is installed so as to wrap in the axial direction and soldered.

Further, the melting point temperature of the solder for connecting the low-temperature terminal and the high-temperature superconductor is different from that of the solder for connecting the low-temperature terminal and the metal-based superconductor.

[0013]

FIG. 2 shows an embodiment of the present invention.
FIG. 5 is a conceptual diagram of a connection portion of a low-temperature terminal of a current lead for a superconducting device.
You. In FIG. 2, reference numeral 60 denotes a metallic superconductor, and 61 denotes a groove.
And the other components are the same as those in FIG.
It is attached. 5 is different from FIG.
Is formed, and NbTi from the coil terminal 50 is
And Nb _ThreeThe metal-based superconductor 60 made of Sn or the like is heated to a high temperature.
By connecting so that it overlaps with the superconductor 222 in the axial direction,
is there. The connection is made electrically and mechanically by soldering. This
At the time of connection between the low-temperature terminal 21 and the high-temperature superconductor 222.
Solder and low-temperature terminal 21 and metal superconductor 60 used
Melting point temperature differs as solder used for connection
Use solder.

According to these configurations, the current is supplied through the normal temperature terminal, the high temperature side lead, the intermediate connection fitting, the low temperature side lead, the low temperature terminal 21, the metal superconductor 60, the coil terminal 50, and the superconducting coil 1. You. FIG. 1 is a detailed view of a low-temperature terminal of a current lead for a superconducting device according to an embodiment of the present invention. In FIG. 1, reference numeral 30 denotes a groove, and other components are the same as those in FIG. 2, and are denoted by the same reference numerals. The difference from FIG. 4 is that grooves 61 or holes are formed on a plurality of surfaces of the low-temperature terminal 21, and a metal-based superconductor 60 is installed in this portion and soldered to electrically and mechanically couple. With this configuration, it is possible to stably supply current to the current lead.

[0015]

According to the present invention, the electrical resistance between the low-temperature terminal and the coil terminal includes the contact resistance due to the surface contact of each terminal and the resistance of the metallic superconductor (including the resistance of each soldered portion). ) And the electrical resistance can be reduced. In the low-temperature terminal, the high-temperature superconductor and the metal-based superconductor are wrapped in the axial direction and soldered, so that the electrical resistance between them can be reduced. Therefore, heat generation due to contact resistance between terminals and Joule heat generation at low-temperature terminals can be reduced, and the amount of heat infiltration into the cryogenic portion can be reduced, so that economical operation of the superconducting device can be expected.

Further, it is difficult to simultaneously perform soldering of the low-temperature terminal and the high-temperature superconductor and soldering of the low-temperature terminal and the metal-based superconductor. Therefore, by using solders having different melting points as solders used for the respective connection parts and controlling the temperature of the connection parts in consideration of the melting point of the solder, it is possible to improve workability at the time of assembling work and to improve reliability. It is possible to realize a connection unit having high reliability.

[Brief description of the drawings]

FIG. 1 is a detailed view of a low-temperature terminal of a current lead for a superconducting device according to an embodiment of the present invention.

FIG. 2 is a conceptual diagram of a connection portion of a low-temperature terminal of a current lead for a superconducting device according to an embodiment of the present invention.

FIG. 3 is a conceptual diagram of a superconducting device using a current lead for a superconducting device according to the prior art.

FIG. 4 is a detailed view of a low-temperature terminal of a current lead for a superconducting device according to the prior art.

FIG. 5 is a conceptual diagram of a connection portion of a low-temperature terminal of a current lead for a superconducting device according to a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Superconducting coil, 21 ... Low temperature terminal, 30, 61 ... Groove,
Reference numerals 40, 51: bolt holes, 50: coil terminals, 60: metallic superconductor, 222: high-temperature superconductor.

Claims (2)

[Claims] A high-temperature side lead made of a copper or copper alloy conductor and a low-temperature side made of a high-temperature superconductor for supplying a current 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. A high-temperature superconductor placed in a groove formed in a low-temperature terminal of the low-temperature side lead and soldered, and one or more surfaces of the low-temperature terminal are connected to the low-temperature side lead. Characterized in that one or more metal-based superconductors from the coil terminals of the superconducting coil are installed and soldered so as to wrap in the axial direction with the high-temperature superconductor in the grooves or holes formed in the superconducting coil. Current leads for superconducting devices. 2. The current for a superconducting device according to claim 1, wherein the melting point of the solder for connecting the low-temperature terminal and the high-temperature superconductor and the melting point of the solder for connecting the low-temperature terminal and the metal-based superconductor are different. Lead.