JP2539772Y2 - Superconducting and normal conducting connection terminals - Google Patents

Description

[Detailed description of the present invention] A. Industrial application field The present invention relates to a superconducting and normal conducting connection terminal.

B. Outline of the device Even when the temperature is reduced from the room temperature to the critical temperature or less, the fitting having a specific value of thermal expansion coefficient prevents the occurrence of thermal stress due to thermal deformation of each member, so that a constant contact force is always maintained. The soft metal washer interposed between the obtained and wound superconducting wire and the normal conducting side is deformed and adhered by the tightening force, and a large contact area is obtained, so that a highly reliable connection terminal is obtained. .

C. Conventional Techniques and Problems There are various problems in connecting a superconducting cable or electric wire to a normal conductor, that is, a conducting wire other than the superconducting conductor.

One of them is the problem of temperature change. In other words, when the superconducting wire reaches a temperature higher than the critical temperature, it becomes normal conducting,
It is necessary to cool below the critical temperature. However, since the connection between the superconducting wire and the normal conducting wire has a connection resistance, the temperature tends to rise. In order to reduce the connection resistance, it is desirable to secure as large a contact area as possible and a uniform contact pressure, but the contact area and the contact pressure become unstable due to thermal deformation. For this reason, heat was sometimes generated due to the connection resistance.

Another problem is the current density. That is, while the critical current of the superconducting material is as large as 10 ⁴ A / cm ^2, generally 1000A / cm ² or less in a normal conducting material, in particular when used in combination with superconducting material, unless its 1/10 This is inconvenient due to heat generation. Therefore, conductors having greatly different sectional areas must be connected.

An object of the present invention is to provide a highly reliable connection terminal between superconductivity and normal conduction which has solved the problems of temperature change and current density.

D. Means and action for solving the problem In the present invention, since the tightening force is applied through the fitting having a specific value of the coefficient of thermal expansion, even when cooling from room temperature to below the critical temperature, thermal deformation is required. And the soft metal washer interposed between the winding part of the superconducting wire and the normal conductor deforms and adheres to each other with the tightening force to obtain a large contact area. Will be done.

E. Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

1 and 2 show a first embodiment of the present invention. As shown in both figures, the bolt 7 penetrates the terminal 2 of the normal conduction, and the superconducting power line 1 is wound around the bolt body 7a above the terminal 2. The superconducting force lines 1 are in the state of the strands whose coating has been stripped. Although a rectangular wire is shown in the figure as the superconducting force line 1, a round wire or a square wire may be used. A normal-conducting casing 4 accommodating a winding portion of the superconducting power line 1 is fitted to the bolt body 7A, and a soft metal such as pure copper or an alloy is provided between the winding portion and the terminals 2 and the casing 4. Washers 3 are interposed. As described above, the current density of the superconducting power line 1 is high, so that the contact area with the normal conducting side (terminal 2, caging 4) can be enlarged and the current density can be reduced so that the superconducting power line 1 is used in the present invention. It was wound so that current could flow through the casing 4 as well as the terminal 2.
Furthermore, since the winding portion of the superconducting power line 1 has a step at the end and tends to have a low flatness, a soft metal washer 3 is interposed therebetween so as to be tightened and deformed as described later, and the contact area is brought into close contact. Is secured. The casing 4 may be made of a hard material so as not to be deformed by the tightening force, and if necessary, fins may be provided on the outer periphery to improve heat conduction. In the present embodiment, the superconducting power line 1 is directly wound around the bolt 7, but a cylindrical core may be attached to the bolt 7, and the superconducting power line 1 may be wound around this core.

Furthermore, a fitting seat is provided on a portion of the bolt copper portion 7A below the terminal 2.
5, the washer 6 is fitted, and the nut 8 is tightened to the lower end of the bolt 7 via these to apply a tightening force. Here, a specific value of the thermal expansion coefficient of the fitting 5 is selected so that thermal stress does not occur due to a temperature change. That is, the superconducting power line 1, terminal 2, a soft metal washer, casing 4, Hamaza 5, each alpha ₁ the thermal expansion coefficient of the washer _6, alpha _2, alpha
_3, α _4, α _5, and alpha _6, respectively the thickness _{L 1, L 2, L 3} , L
_4, and L _5, L _6. Further, the coefficient of thermal expansion of the bolt 7 is α _B , and the length of the metal fastening portion is L _B. Then, when the whole is cooled or heated to cause a temperature change T, the thermal deformation λ _T1 of the bolt 7 and the total λ _T0 of the thermal deformation of each member outside the bolt 7
Is represented by the following equation.

λ _T0 = (L ₁ · α ₁ + L ₂ · α ₂ + ₂ L ₃ · α ₃ + L ₄ · α ₄ + L
_{5 · α 5 + L 6 ·} α 6) · T λ T1 = L B · α B · T where, λ _T0 = λ _T1 to become such L _5, selects the alpha _5. With this configuration, thermal stress due to temperature change is prevented. Therefore, after assembling the connection terminal of the present invention at normal temperature, cooling to below the critical temperature to bring the superconducting power line 1 into a superconducting state. However, the tightening force of the bolt 7 does not change and always has a constant value. Therefore, a constant contact surface pressure is always obtained, and the contact resistance does not increase.

Here, as a specific example in the current technology, the soft metal washer 3 and the washer 6 are omitted because they are thin and will be considered.

Further, the length relation was assumed as follows. However, the length of the casing 4 L _4, the length of Hamaza 5 L _5, the length L ₂ terminal 2, the length of the bolt 7 and the L _B.

L ₄ + L ₂ = a L ₅ = 2a L _B = 3a Therefore, as shown in the following equation, the thermal deformation amount λ _T1 of the bolt 7 due to the temperature change due to the temperature change and the total thermal deformation amount λ of the fastening object
_{If T0} is equal, there will be no change in fastening pressure. However, the thermal expansion coefficient of Hamaza 5 and alpha _5, the temperature change T.

Thermal deformation λ _T0 = aT × 10 × 10 ⁻⁶ + 2aT × α Thermal deformation of ₅ volts λ _T1 = 3aT × 5.6 × 10 ^-6 where α ₅ is obtained as λ _T0 = λ _T1. .

3aT × 5.6 × 10 ^-6 = aT × 10 × 10 ^-6 + 2aT × α ₅ ∴ 16.8 × 10 ^-6 = 10 × 10 ^-6 + 2α ₅ ∴ α ₅ = (16.8-10) × 10 ^-6 /2=3.4 × 10 ^-6 Therefore, a material having a thermal expansion coefficient α ₅ = 3.4 × 10 ^-6 is fitted with the seat 5.
It will be good to choose as. Specifically, there is an alloy of tungsten and vanadium showing a value close to this, and this may be used.

As is apparent from this result, the material of the fitting 5 should be appropriately changed according to the structure, dimensions, and the material thereof. For example, if an aluminum bronze bolt is used, its thermal expansion coefficient will be 12-14 × 10 ^-6 , for example,
If 13 × 10 ⁻⁶ , α ₅ = 8 × 10 ⁻⁶ , and a material close to this value is, for example, a type of Ni steel.

Furthermore, in the future, when ceramic-based superconducting wires and oxide superconducting wires are put into practical use, or when superconducting wires near normal temperature (around 220 ° K) are put into practical use, the thermal expansion coefficient will be greatly increased. As a result, the material of the seat also changes significantly.

Next, a second embodiment of the present invention will be described with reference to FIGS. In the embodiment shown in the figure, a greater tightening force can be obtained by increasing the number of bolts 7 wound on the superconducting force lines 1 from one to three. A spacer 9 is interposed between the bolts 7 to prevent the superconducting power lines 1 from escaping. Since the other configuration is the same as that of the above-described embodiment, the same members are denoted by the same reference numerals and description thereof will be omitted.

In the above embodiment, the bolt and the nut were used as the simplest and most reliable method for generating the tightening force. However, there is no reason to stick to the bolt and the nut. good.

F. Effects of the Invention As described above, the present invention uses a fitting having a specific coefficient of thermal expansion as described specifically based on the embodiment. A constant contact pressure is ensured and there is no increase in temperature due to contact resistance. Furthermore, the contact area is enlarged by winding a superconducting wire,
There is an advantage that the current density can be reduced, and since the connection is not semi-permanent by brazing or welding, it can be disassembled without cutting. In addition, since the structural adhesion between the superconducting wire and the normal conducting side is excellent, there is an advantage that the current density can be relatively increased and the device can be downsized.

[Brief description of the drawings]

1 is a sectional view showing a first embodiment of the present invention, FIG. 2 is a sectional view taken along the line II-II in FIG. 1, FIG. 3 is a sectional view showing a second embodiment of the present invention, FIG. 4 is a sectional view taken along line IV-IV in FIG. 3, and FIG. 5 is an assembled perspective view of the second embodiment. In the drawings, 1 is a superconducting force line, 2 is a normal conducting terminal, 3 is a soft metal washer, 4 is a normal conducting casing, 5 is a fitting, 6 is a washer, 7
Is a bolt, 8 is a nut, and 9 is a spacer.

Claims (1)

(57) [Scope of request for utility model registration] 1. A superconducting wire is wound around a core connected to a normal conducting terminal, and a normal conducting casing for accommodating a wound portion of the superconducting wire is fitted to the core, and furthermore, the winding portion is And a soft metal washer between the terminal and the casing, and a fitting seat having a coefficient of thermal expansion that does not cause thermal stress due to the sum of thermal deformations of the members, and tightening along the core body. Superconducting and normal conducting connection terminals characterized by applying force.