JPS58172876A - Method of connecting superconductive conductor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] This invention relates to a method for connecting superconducting wires.

A perspective view of a general superconducting wire is shown in FIG. 1(a), and a cross-sectional view is shown in FIG. 1(b). In the figure, (1) is a superconducting wire, (2)
is a low-resistance base material (copper is commonly used), (
3) is a superconductor filament. Low resistance base material (2)
is used to electrically and thermally stabilize the superconducting filament (3). Superconducting wire (1) critical/M +
When cooled to below f, the electrical resistance of the superconductor filament (3) becomes zero. Therefore, when a current is passed through the superconducting wire (1), the current flows through the superconducting filament (3).

Conventionally, the superconducting wire (1) was connected as shown in FIG. In the figure, (4) is solder for connecting the superconducting wires (1) to each other. Various solder materials are used, such as indium, lead/tin, silver/lead/tin, etc. FIG. 8 is a sectional view showing the principle of a conventional connection method for superconducting wires (1). Here, it is assumed that superconductor (1) is used in a superconducting state. Arrows in the figure indicate the flow of current. That is, from one superconductor filament (3),
Low resistance substrate (2) s'' layer (4), through the low resistance substrate (2) and the other superconductor filament (3)
current flows into. Low resistance base material (2) and solder layer (4)
) generally has electrical resistance. Note that the solder layer (4
) becomes a superconductor in a low magnetic field and low current density, but in a superconducting coil, it is generally in a normal conductor state due to the magnetic field and current.

Therefore, at the junction of the superconducting wire (1), resistance loss occurs when current transfers from one superconducting filament (3) to the other superconducting filament (3). The electrical resistance of this connection is generally less than 10''fΩ.

Now, let us consider persistent current operation of a superconducting coil. A diagram of this principle is shown in FIG. In the figure, qo is superconducting wire (1)
0 is the superconducting wire (IQ and excitation power supply 07), and 0 is the persistent current switch. , 0 is the heater 50G is the thermal insulator, 09 is the heater power supply, and 09 and (a) are the switches. coil ocJ
It is assumed that the main circuits such as the power supply and persistent current switch are cooled with liquid helium. Close the switch (E) and turn on the heater α.
When the persistent current switch q3 is heated with plaster, the temperature of the persistent current switch 0 becomes higher than the critical temperature of the superconducting wire (1) due to the presence of the thermal insulator (c). Therefore, the persistent current switch ceases to be in a superconducting state and has a resistance of 1 Ω. In this state, when switch 4 is closed, superconducting coil αQ is excited by excitation power source 07). FIG. 5 represents this state using an equivalent circuit. Here, (2) represents the sum of the normal conduction resistance of the permanent ′ (current switch RO and the resistance of the connecting part αυ). After exciting the superconducting coil αQ to a constant current of 1o, open the switch (E). Stop heating heater a<, and turn on the persistent current switch (to)
is cooled to a temperature higher than the critical temperature of the superconducting wire (1). If you do this.

The terminals of the superconducting coil αQ are short-circuited by a superconducting wire with zero electrical resistance. If the switch 0 is opened in this state, the current in the superconducting coil OQ circulates through the permanent current flow switch (3). In other words, a super single conductor coil (1
0 is operated with persistent current. , this state is shown in an equivalent circuit in FIG. In the figure, the arrow represents the current, (
2) represents the resistance of the connection 0]).

The time (1) change in superconducting coil current I during persistent current operation is described by the following equation.

1 = Io e L” However, IO = initial current value, L=1! the inductance of the conducting coil, R = resistance of the connection.

As a typical numerical example, the inductance L of a superconducting coil
Assuming that IH is IH and the resistance R of the connection part is 101Ω, it is calculated from the above equation that it will take 122 days for the superconducting coil current I to attenuate to 90% of its initial value. Note that the decay time constant τ-(=VR) of the superconducting coil current I is IC seconds. That is, after 8 months of persistent current operation of the superconducting coil, the heel flow value has decreased to 90%.

Since the magnetic field generated by the superconducting coil is proportional to the current, the magnetic field is also reduced by 90%. This is because the energy stored in the superconducting coil is consumed as resistance loss due to the presence of electrical resistance at the connection portion of the superconducting wire.

In a superconducting coil that requires a constant supermagnetic force and a constant magnetic field, such as a superconducting coil for a magnetic levitation train or a superconducting coil for a nuclear magnetic resonance system (d), current attenuation as described above is not preferable.

As described above, the conventional superconducting wire connections have the disadvantage that electrical resistance exists, and when the superconducting coil is operated in permanent permeation mode, the current in the superconducting coil is attenuated.

This invention was made in order to eliminate the above-mentioned drawbacks of the conventional method by bundling superconducting filaments and bonding them together using a reservoir liquid.

The purpose of this research is to discover and provide a method for connecting superconducting wires that can reduce the electrical resistance to zero.

An embodiment of the present invention will be described below with reference to the drawings. 7th
Figures (a) and (b) are perspective views (
1) and a cross-sectional view of I. In the figure, the arrow indicates 1st class,
(5) is a gold A film. Two super, buried a O)
Remove the low resistance substrate (2) at the end (the copper substrate is easily dissolved with nitric acid), take out the superconducting filaments (3), bundle them and surround them with a metal film (5).

After doing so, the superconducting filament bundles are welded together. The metal film (5) prevents the superconducting filament (3) from fusing and scattering during welding. or.

If the metal film (5) is made of a metal with a higher resistance than the normal temperature superconductor, the superconducting filament bundles can be welded together by spot welding.

In this way, since the superconducting filaments are connected to each other by welding, when the superconducting edge connection portion of the present invention is cooled to an extremely low temperature with liquid helium or the like, the electrical resistance of the connection portion becomes zero. Therefore, if a superconducting coil is operated permanently, no reduction in current will occur.

FIG. 8 is a sectional view showing another embodiment of the present invention. In order to improve the electrical stability of the connection, solder another superconducting wire (1) or a wire with a sufficiently low 1K resistance to the connection (4).
It's something new. Here, the metal fin (5) must be made of a metal (copper alloy, nickel alloy, etc.) that can be soldered. Figures 9 to 11
The figure shows another embodiment of the invention.

Although the orientation of the connecting portions is different from those shown in FIGS. 7 and 81, the connection method is essentially the same as that shown in FIGS. 7 and 8.

As described above, according to the present invention, the base material at the end of two superconducting wires is removed, the superconducting filaments of the two superconducting wires are bundled, surrounded by a metal film, and welded, so that the superconducting filaments are fused. There is a young fruit that can connect superconducting filaments to each other without scattering, and can reduce the connection resistance between superconducting wires to zero.

[Brief explanation of drawings]

Figures 1(a) and 8(b) are perspective views and cross-sectional views showing general superconductor wires, Figures 2 and 8 are perspective views and cross-sectional views showing conventional superconductor 4-wire connection methods, Figure 4 shows the excitation circuit of a superconducting coil with a permanent flow switch, Figure 5 shows the equivalent circuit during excitation of the superconducting coil, and Figure 6 shows the equivalent circuit of a superconducting coil during permanent '1 flow operation. (a) and (b) are perspective views and cross-sectional views showing one embodiment of this invention, No. 8
9, 10, and 11 are sectional views showing other zero-relaxation examples of the present invention. (1)...Super single conductor wire, (2)...Base material, (3)...
- Superconducting base material, (4)... Hunter layer, (5)... Metal film. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Agent Makoto Kuzuno - Figure 1 [Figure 3 Figure 4 Figure 5 Figure 6 Procedural amendment (voluntary) Mr. Commissioner of the Japan Patent Office 1, Indication of case Japanese Patent Application No. 57-558118 2
, Name of the invention, Method for connecting superconducting wires 3, Relationship with the amended case Patent applicant address 2-2-3 Marunouchi, Chiyoda-ku, Tokyo Name (601) Mitsubishi Electric Corporation Representative Jinhachibe Katayama 4. Address of the agent: 2-2-3-5 Marunouchi, Chiyoda-ku, Tokyo; Subject of amendment (3) Brief description of drawings in the specification column 6; Contents of amendment (1) Attach the scope of claims. (2) In the specification, "superconductivity" on page 2, line 20 is corrected to "superconducting wire J." (3) "Supermagnetic force" on page 6, line 8 of the specification is corrected. 1.
"Magnetomotive force" is corrected. (4) In the same article, page 9, line 1, “superconducting base material” and “Azuke” are written as “
Correct it to superconducting filament J. 7. List of attached documents (1) Documents stating the scope of claims One or more copies Claims (1) Superconducting filaments obtained by removing the base material of superconducting wire are bundled, surrounded by a metal film, and the superconducting filament is A method of connecting superconducting wires characterized by welding filaments. (2) A superconductor according to claim 1, characterized in that the metal film surrounding the superconducting filament at the connection portion of the superconducting wire is a metal film having a resistivity at room temperature equal to or higher than that of the superconducting filament. How to connect lines. (3) The method for connecting superconducting wires according to claim 1, characterized in that the metal film surrounding the superconducting filament at the connection portion of the superconducting wire is a metal film that can be soldered. (4) The method for connecting superconducting wires according to claim 1, wherein another superconducting wire or a resistance wire is soldered to the connecting portion of the superconducting wire and before and after the connecting portion of the superconducting wire. 3371

Claims (1)

[Scope of Claims] (1) A method for connecting superconducting wires, which comprises bundling superconducting filaments obtained by removing the base material of superconducting wires, surrounding them with metal filaments, and welding the superconducting filaments. (2) The superconductor according to claim 1, characterized in that the metal filament surrounding the superconducting filament at the connection portion of the superconducting wire is a metal film having a resistivity at room temperature equal to or higher than that of the superconducting filament. The subjunctive of kando-kei. 2. The method for connecting superconducting wires according to claim 1, wherein the metal filament surrounding the superconducting filament at the connection portion of the superconducting wire is a gold 14 filament with a circular portion for soldering. (4) A method for connecting a superconducting wire according to claim 1, characterized in that another superconducting wire or a low resistance spring is soldered to the connecting portion of the superconducting wire and before and after the superconducting wire. .