JPS5916208A - Connected superconductive wire - 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 The present invention relates to connected superconducting wires, and particularly to the configuration of a connecting portion of a superconducting wire.

Generally, a superconducting wire has a structure as shown in FIGS. 1A and 1B of the accompanying drawings. That is, in the figure, the symbol /
is a superconducting wire, and ko is based on low resistance, and generally a copper phase is often used. Further, 3 is a superconductor filament. The low resistance base material λ is used to electrically and thermally stabilize the superconductor filament 3. Now, when the superconducting wire is cooled below the critical temperature (generally at a temperature of 11.0K with liquid helium), the superconducting filament 3
The electrical resistance of becomes zero. Therefore, when a current is applied to the superconducting wire under this condition, the current flows through the superconducting filament 3.

Conventionally, superconducting #i! has such a configuration. The / connections were made as shown in Figure 1 of the attached drawings. That is, in the figure, the symbol ``da'' indicates a solder layer for connecting the superconducting wires 1 to each other, and an alloy of lead and tin is generally used as the material for this solder layer. The flow of current in a conventional connection section between superconducting wires constructed in this manner is shown in principle in a vertical sectional view of the connection section as shown in FIG. 5 of the accompanying drawings. However, here, it is assumed that the superconducting wire / is used in a superconducting state.

In the figure, arrows indicate the flow of current. That is, a current flows from one superconducting filament J, through its low resistance base material, the solder layer, and the low resistance base material on the other side, to the superconducting filament 3' of the other superconducting wire /'. Flow into. In this case, the low resistance base materials 2, . 2' and the solder layer generally have electrical resistance, but this low resistance base material, 2, .
Generally, steel is often used for 2', and the electrical resistivity of copper is 2X10' at liquid helium temperature.
It is about Ω. On the other hand, the solder layer becomes superconducting in a low magnetic field and low current density, but in a superconducting coil it is generally in a normal conducting state due to the magnetic field and current, and therefore its electrical resistivity is approximately y×io'Ωα at the liquid helium temperature. Therefore, in the superconducting wire/component connection, when current is transferred from one superconducting filament 3 to the other superconducting filament 3', resistance loss occurs in the low resistance base plate and the solder layer. However, if the thickness of the solder layer is thin enough,
The resistance loss in the solder layer is smaller than the resistance loss in the low resistance base material 2. However, in actual O-soldering operations, it is impossible to reduce the thickness of the solder layer sufficiently due to distortions and irregularities on the surface of the superconducting wire. That is, the presence of the solder layer, which has an electrical resistivity about θ times higher than that of the low-resistance base material, plays a large role in the resistance loss at the connection portion.

Now, considering the persistent current operation of a superconducting coil,
The principle diagram is as shown in Fig.
0 is a superconducting coil wound with superconducting wire l, // is superconducting 1%! Connection part /2 is a lead that connects the superconducting coil 10 and excitation power source 17 via connection part /6, /3 is a persistent current switch, /4t is a heater, /left is a thermal insulator, 7g
is a heater power supply, /q and 20 are switches. However, it is assumed that the main circuits such as the coil IO and the persistent current switch are cooled by liquid helium. In this condition, switch θ is closed and heater/4'
When persistent current switch/3 is heated by
Due to the presence of 5, the temperature of persistent current switch /3 becomes above the critical temperature of superconducting wire /.

Therefore, the persistent current switch 13 is no longer superconducting and has electrical resistance. In this state, when the switch /9 is closed, the superconducting coil /θ is excited by the excitation power supply /7. This state is expressed by an equivalent circuit as shown in FIG. 5 of the accompanying drawings. Here, the sign, 2
/ represents the sum of the normal conduction resistance of the persistent current switch /3 and the resistance of the connecting portion //. Here, superconducting coil 10
A constant current engineer. After the superconducting wire is energized, the switch 20 is opened to stop heating the heater 4', and the permanent current switch 3 is cooled down to a temperature below the critical temperature of the superconducting wire. In this way, the terminals of the superconducting coil 10 are short-circuited by a superconducting wire with zero electrical resistance. If switch /9 is opened in this state, the current in superconducting coil 10 will circulate through persistent current switch J. That is,
The superconducting coil will be operated with persistent current.

This state is shown in an equivalent circuit in FIG. 6 of the accompanying drawings. In the figure, the arrow represents the current, and the symbol λλ represents the connection point //
represents the resistance of

Now, if we express the current change of the supercurrent coil in the case of persistent current operation in this way, the following equation is obtained. In other words, I, - initial current value - inductance Ro + Rs of the superconducting coil - resistance Ro of the connection part - resistance R8 of the low resistance base material λ = resistance of the solder layer Hiroshi Here, as a typical numerical example, the low resistance base Assuming that the thickness of the part of the material through which the current flows is twice the thickness of the solder layer, and the resistance Rs of the solder layer is 10', the resistance R8 of the low resistance base layer is 2× /θ−7Ω. Also, if the inductance L of the superconducting coil is /H, the coil current I is the initial current value. The period for decay to q,t% of is calculated as 50 days from the above formula. This is because the energy stored in the superconducting coil was consumed as resistance loss due to the presence of electrical resistance at the connections of the superconducting wire. For example, when such a superconducting coil is used as a superconducting coil for a magnetic levitation train, a certain magnetomotive force and a certain magnetic field are required. The smaller the current attenuation, the better.

As described above, in the connections of conventional superconducting wires, there is a resistance of the low-resistance base material and a resistance of the solder layer, and the resistance of the solder layer is higher than the resistance of the low-resistance base material. Therefore, when the superconducting coil is operated with persistent current, the attenuation of the current in the superconducting coil is due to the resistance caused by the solder layer.
It had the drawback of being thick.

An object of the present invention is to provide a connected superconducting wire capable of eliminating the above-mentioned drawbacks of the conventional connected superconducting wire and reducing the electrical resistance of the connecting portion of the connected superconducting wire. It is.

In order to achieve this object, the present invention provides a method in which the connecting portions of the connected superconducting wires overlap each other, the connecting portions are housed in a connecting tube, and each connecting portion is The superconducting wires are crimped together with the connecting tube to ensure good conduction between the superconducting wires to be connected and the connecting tube.

Hereinafter, the present invention will be explained based on FIG. 7 of the accompanying drawings showing one embodiment thereof. In the figure, arrows indicate current, sign /, /
' is the superconducting wire to be connected, λ, 2' is its low resistance base material,
3 is a superconducting filament that is equivalent to that in the conventional device, and the symbol 3/ is each superconducting wire /, /'
This is a connection tube that houses the connection part of the inside.

That is, for example, the ends of two superconducting wires /, /', which are the connection parts, are stacked on top of each other, the overlapped parts are placed inside the connection tube 3/, and the connection tube 3/ is pressed from the outside. The superconductors 1fiJ/,/' are electrically connected without using a solder layer. In this way, the low resistance base materials 2, . superconducting wire l,/' without passing through a solder layer with higher electrical resistivity than 2'
As a result, the connection resistance of the connection part can be kept low, and therefore, even when the superconducting coil is operated with persistent current, the attenuation of the current in the superconducting coil is lower than in the case of a connection with a solder layer. There will be very few. Now, by substituting the above-mentioned representative values into the above equation, in the case of the connected superconducting wire according to the present invention, the time required for the current to reach qr% of the initial current value is actually 3θO days. Calculated.

Furthermore, if the connecting tube J/ has conductivity, the attenuation of the current will be smaller. Although the above embodiments have been described in the case where the number of superconducting wires to be connected is small, the invention is not limited to this. For example, as shown in the attached drawings, three or more superconducting wires are connected. Even if it is, the connection can be made with the same configuration and the same effect can be achieved.

In addition, what is shown in FIG. 9 of the accompanying drawings is another embodiment in which other superconducting wires are connected across the superconducting wires /, /' and the connecting tube 3/ to increase electrical stability. Alternatively, a connection stabilizing member J2 made of a low resistance conductor is connected by providing a solder layer 33 by soldering. Furthermore, what is shown in Figure 1θ of the attached drawings is the superconducting wire to be connected /, /
The direction of ' is different, and the effect is the same as that of FIGS. 7 and g. Furthermore, a connecting member may be provided according to FIG. 9.

Since the present invention is constructed and operates as described above, it is particularly necessary to use a solder layer with high electrical resistivity at the connection portion thereof. Therefore, it is possible to obtain a superconducting wire having a connection portion with extremely low electrical resistance. We were able to achieve five effects.

[Brief explanation of the drawing]

Figure 1 is an external perspective view of a general superconducting wire (cross-sectional view (B)), Figure 2 is an external perspective view of a superconducting wire with a conventional connection structure, and Figure 3 is an external perspective view of a conventional connection structure. Fig. 9 is an excitation circuit diagram of a superconducting coil with a persistent current switch, Fig. 5 is an equivalent circuit diagram during excitation of a superconducting coil, and Fig. 6 is an equivalent circuit of a superconducting coil in a persistent current operating state. Fig. 7 is an external perspective view showing seven embodiments of the present invention, and Figs. g to 1O are external views of other embodiments of the present invention. 1.L'...Low resistance base material, 3.3'...Superconductor filament, 33.
- Solder layer, 31... Connection tube, 32... Connection stability member. In each figure, the same reference numerals indicate the same or corresponding parts. Agent Shin Kuzuno −

Claims (1)

[Claims] (1) The connecting portions of the connected superconducting wires are such that the connecting portions of the superconducting wires to be connected overlap each other, the connecting portions are housed in the connecting tube, and each connecting portion is placed in the connecting tube. 1. A connected superconducting wire characterized in that the superconducting wires are crimped together to provide good electrical conductivity between each superconducting wire and a connecting tube. (,2) The connected superconducting wire according to claim 1, wherein the connecting tube is made of a conductive material. (3) A structure that ensures good conduction between the superconducting wires to be connected and the connecting tube consists of either another superconducting wire or a low-resistance conductor across each superconducting wire to be connected and the connecting tube. The connected superconducting wire according to claim 1 or 2, which is constructed by electrically joining members for connection stabilization.