JPH05135944A - Superconducting apparatus - Google Patents

Abstract

PURPOSE:To increase the current capacitance of the joint of a current lead connection terminal and a superconductor wire by comprising the connection terminal having a spiral zone and the superconductor wire which connects it so as to short-circuit the turn of the spiral zone. CONSTITUTION:An extremely fine multicore superconducting wire having several ten thousand superconductor filaments of a diameter of 1mum or less is used as a superconductor wire 1, and every filament is surrounded by CuNi of relatively high electric resistance. Every element wire is kept surfaced with a CuNi layer. This superconductor wire is a plural-order strand and is connected by twist back to the strand one level before in the connection terminal 6. The connection terminal 6 is wounded in a spiral form. This constitution makes current shunt gradually from the connection terminal 6 to the superconductor wire 1 by the effect of the inductance of the connection terminal's spiral zone. This can provide a superconducting apparatus having a joint of high current capacitance and low loss of heat generation and the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting device, and more particularly to a structure for connecting a superconducting wire drawn from a superconducting coil or the like with a current supply lead.

[0002]

2. Description of the Related Art A superconducting coil at a cryogenic temperature is supplied with current from a power source in a room temperature space by a current lead made of a copper plate or the like. That is, as shown in FIG. 5, the connection between the superconducting wire 1 and the current lead 2 is provided in a cryogenic atmosphere in the container 3 or in a coolant such as liquid helium 4.
At this time, in order to prevent the transition (quenching) of the superconducting wire to the normal conducting state due to heat generation at the connection portion, the connection resistance is kept low by making the connection portion long.

[0003]

However, when a current having a large rate of change in current, such as an alternating current, is applied to the superconducting coil, the current is gradually shunted from the current lead to the superconducting wire in the entire connecting portion. However, a relatively large current flows to the tip of the current lead, and the heat generated therein may heat the superconducting wire, causing a transition (quenching) from the superconducting state to the normal conducting state. An object of the present invention is to provide a superconducting device that has a large current capacity at a connecting portion of a current lead and a connecting portion of a superconducting wire and little heat generation.

[0004]

The superconducting device of the present invention comprises:
A superconducting wire from a superconducting coil or the like is connected so that each turn of the spirally wound connection terminal is short-circuited.

[0005]

With this structure, an inductance is generated by the spiral portion of the connection terminal, and the current is shunted to the superconducting wire in a good condition.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a main part of this embodiment.
As the superconducting wire 1, an ultrafine multicore superconducting wire having tens of thousands of superconducting filaments having a diameter of 1 μm or less is used. Also, each filament is surrounded by CuNi, which has a relatively high electric resistance, in order to reduce the loss during AC energization. In addition, in order to prevent the coupling current from flowing between the wires, C is also applied to the surface of each wire.
A layer of uNi is provided. This superconducting wire is a twisted wire of a plurality of orders, and in this embodiment, the connection terminal 6 is twisted back to the previous level of twisted wire and connected. The connection terminal 6 is spirally wound. In addition, although each turn of the connection terminal 6 is separated in this embodiment, each turn may be insulated by an insulator or the like.

With the structure of this embodiment, the current is gradually shunted from the connection terminal 6 to the superconducting wire 1 by the effect of the inductance of the spiral portion of the connection terminal. This will be described with reference to FIG. 2 showing an equivalent circuit of the connection portion.
In this figure, Lcu is the inductance of the connection terminal, R
cu is the resistance of the connection terminal, Lsc is the inductance of the superconducting wire, and Rcon1 and Rcon2 are the connection resistances. At this time, Rco
If the currents flowing through n1 and Rcon2 are I1 and I2 respectively,

[0009]

[Equation 1]

That is, in this case, the current is gradually shunted to the superconducting wire. On the other hand, when energizing an alternating current of 50 Hz, it is necessary to consider the inductance. Generally, the inductance of a thin wire is larger. Therefore, when alternating current is applied, it is difficult for the thin wire, that is, the superconducting wire, to flow. This corresponds to Lsc> Lcu in the above equation. Further, in the present embodiment, since the superconducting wire 1 is symmetrically connected to the connection terminal 6, there is no imbalance of the shunt current in each twisted wire of the superconducting wire 1. Further, generally, the skin depth δx when an alternating current is applied is given by the following equation.

[0011]

[Equation 2] Where ω: angular frequency, μ: permeability, σ: electrical conductivity

The skin thickness δx when an alternating current is applied to the connection terminal at an extremely low temperature is about 1 mm. Therefore, when the thickness of the connection terminal is 2 mm or more, the apparent resistance of the connection terminal increases and heat generation increases. Therefore, even when a solid conductor is used, almost no current flows in the central portion due to the skin effect when an alternating current is applied. However, a hollow copper pipe is used for the connection terminal 6 in this embodiment. Therefore, there are few parts that are wasted when energized. In this way, according to the present embodiment, it is possible to configure the connection terminal that generates less heat when an alternating current is applied. (Other embodiments)

FIG. 3 is a diagram showing a main part of another embodiment of the present invention. The connection terminal 7 is a copper rod processed with a spiral groove. Also in this embodiment, the superconducting wire 1 is untwisted to the previous stranded wire at the connection terminal 7 and connected.

Since the superconducting wire 1 is symmetrically connected to the connecting terminal 7, there is no imbalance of the shunt current in each twisted wire of the superconducting wire 1. Further, the connection terminal 7 in the present embodiment has good manufacturability because it is only necessary to spirally form a groove on a copper rod.

FIG. 4 is a diagram showing a current supply terminal in still another embodiment of the present invention. The connection terminal 8 is a copper pipe in which a groove is spirally processed. In this embodiment, since there are relatively many grooves, the FRP for reinforcement is provided in the copper pipe.
The reinforcing cylinder 9 is inserted. However, depending on the number and length of the grooves, the reinforcing cylinder 9 may be put in only a part of the copper pipe, or may be unnecessary. Further, in the present embodiment, the groove is not particularly provided with a spacer or the like, but an insulator such as FRP may be filled for processing. In this embodiment, since the superconducting wire 1 is symmetrically connected to the connection terminals, the imbalance of the shunt current in each twisted wire of the superconducting wire 1 is eliminated.
Also, since a copper pipe is used, there is little wasteful part due to the skin effect.

[0016]

As described above, according to the present invention, it is possible to provide a superconducting device having a connection portion having a large current capacity and a small loss such as heat generation.

[Brief description of drawings]

FIG. 1 is a diagram showing a connecting portion of a superconducting device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an electrical equivalent circuit of a connection portion in the superconducting device of the present invention.

FIG. 3 is a diagram showing a connecting portion of a superconducting device according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a connecting portion of a superconducting device of a third embodiment of the present invention.

FIG. 5 is a view showing a connecting portion in a conventional superconducting device.

[Explanation of symbols]

 1 ... Superconducting wire 2 ... Current lead 3 ... Container 4 ... Liquid helium 5 ... Superconducting coil 6, 7, 8 ... Connection terminal 9 ... Reinforcing cylinder

Claims (1)

[Claims] 1. A superconducting device comprising: a connection terminal having a spiral portion; and a superconducting wire connected so as to short-circuit the turns of the spiral portion.