JPH10126917A - Terminal structure of superconducting cable conductor and jointing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a terminal structure, for a superconducting cable conductor having such a structure as a superconducting wire is wound in layer around a core member which can be formed through a simple process while decreasing the resistance. SOLUTION: At the terminal part of a superconducting cable conductor 20 where a superconducting wire is wound in layer around a core member, the wire of each layer is removed partially to form a structure where the wires 21a, 21b, 21c, 21d of respective layers are exposed selectively. The exposed layers are then bonded, respectively, with terminal members 10a 10b, 10c, 10d. The terminal member 10a-10d has a ring part into which the conductor is inserted and secured in place by soldering.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a terminal structure of a superconducting cable conductor capable of transmitting a large amount of current with low loss and a method of connecting the terminal structure.

[0002]

2. Description of the Related Art Oxide superconducting wires such as Bi222
(3) Since the high-temperature superconducting tape wire can be used at the temperature of liquid nitrogen, has a relatively high critical current density, and can be easily made longer, it is expected to be applied to superconducting cables and magnets. Research has been conducted on superconducting cables composed of Bi2223 high-temperature superconducting tape wires,
Conductors are being manufactured.

FIG. 12 shows a specific example of a cable conductor having a structure in which a large number of tape wires are assembled on a former. FIG.
As shown in FIG. 2A, the superconducting cable conductor has, for example, a structure in which a superconducting wire is wound around the former 110 in four layers. A plurality of wire rods 101a, 101b, 10 are provided on the first, second, third and fourth layers, respectively.
1c and 101d are spirally wound around a cylindrical former 110. FIG. 10B shows a side surface of the cable conductor, and the outermost layer of the tape-shaped wire 10
1d shows a state of being spirally wound. Also,
Between the first layer and the second layer, between the second layer and the third layer, and between the third layer and the fourth layer, insulating layers 102a and 102
b and 102c are provided.

When power is supplied to a conductor as shown in FIG. 12, it is necessary to perform some processing on the terminal. For example, as for the portion from the end of the conductor to a predetermined length L as shown in FIG. 12B, all the wires except for the insulating layer can be integrated by soldering. When performing such integration, in order to make the connection resistance of the terminal portion as small and uniform as possible, it is possible to form an integrated structure by soldering the wires one by one.

[0005]

In the case of industrially producing long conductors by mechanically assembling wires, a method of soldering wires one by one to form a terminal portion is inefficient. is there. Further, according to the work of performing the soldering one by one, the connection resistance always reaches a high level of several μΩ, and the resistance value also varies relatively largely by the work. Therefore, it is required to form a terminal structure by simpler and more reliable processing. Also, the resistance of the terminal portion is desirably smaller, and the resistance value of each product is desirably smaller.

Further, in a multilayer conductor, there is a high possibility that a drift phenomenon in which a current value flowing in each layer becomes uneven due to a difference in impedance between the layers. In that case, the amount of AC loss generated in the conductor depends on the current distribution,
It is necessary to grasp the characteristics such as the distribution of the conduction current for each layer. Further, when a drift phenomenon in which a current flows first from the outer layer of the conductor occurs, there is a possibility that an AC loss is increased as compared with a case where a current flows uniformly in each layer. Also,
If the insulation between the layers is not ensured, the current conductance occurs due to the contact conductance between the layers,
This results in increased losses.

An object of the present invention is to provide a terminal structure which can be formed by a simple process and has a small resistance value.

A further object of the present invention is to provide a terminal structure capable of measuring a current value of each layer in a cable conductor in which superconducting wires are assembled in layers.

It is a further object of the present invention to provide a means by which the current distribution between layers in a superconducting cable conductor can be made uniform.

[0010]

According to the present invention, there is provided a terminal structure of a superconducting cable conductor having a structure in which a plurality of superconducting wires are wound in a layer around a core material, wherein a wire material in an outer layer of the plurality of wires is provided. The outer layer portion present on the surface, the terminal member provided around the outer layer portion and joined to the wire material in the outer layer portion, and the wire material in the inner layer without the wire material in the outer layer of the plurality of wire materials is exposed. And a terminal member provided around the inner layer portion and connected to a wire rod in the inner layer portion.

The terminal structure according to the present invention preferably has a structure in which the wires of each layer are selectively exposed in order from the outermost wire to the innermost wire as the terminal ends of the cable conductor. A terminal member is bonded to each of the exposed layers.

In the terminal structure of the present invention, it is preferable that the terminal members provided on each layer are electrically insulated from each other by the insulating material between the outer layer and the inner layer.

[0013] The terminal member for bonding to each layer may have an annular portion surrounding the wire layer and a projection protruding from the annular portion. Each layer of the cable conductor can be inserted into and joined to the annular portion of such a terminal member. Also, a Rogowski coil can be inserted into the projection of the terminal member. When the terminal member having the annular portion and the protruding portion is provided for each layer, by inserting a Rogowski coil into the protruding portion of each terminal member, it is possible to detect the current distribution for each layer.

It is preferable that the terminal member constituting the present invention is provided so as to surround the layer of the wire, and is joined by pouring a solder between the member and the wire. For example, a predetermined layer portion at the end portion of the cable conductor can be inserted into a ring-shaped terminal member, and solder can be poured between the terminal portions and fixed. The distance between the ring-shaped terminal member and the cable conductor terminal inserted into the ring-shaped terminal member is set to a predetermined value so that the poured solder flows thinly and uniformly. Further, a hole for pouring the solder can be formed in the terminal member.

According to the present invention, the resistance value of the terminal portion to which the terminal member is joined can be made 1 μΩ or less.

The present invention is applied to a conductor in which a superconducting wire is wound in two or more layers in a core shape. The superconducting wire wound in a core shape can be, for example, an oxide superconducting wire. In particular, (Bi, Pb) ₂ Sr ₂ Ca ₂ Cu ₃ O
_The present invention is preferably applied to a cable conductor in which a tape-shaped wire having a bismuth-based 2223-phase oxide superconductor such as _10-X (0 ≦ X <1) and a stabilizing matrix covering the same is wound in a layered manner. Can be. In this tape-shaped wire, silver or a silver alloy is used for the stabilizing matrix.

Further, the present invention provides a method for electrically connecting the terminal structures described above. The terminal member joined to the outer layer in one terminal structure of the pair of terminal structures to be connected is joined to the terminal member joined to the inner layer in the other terminal structure. Further, the terminal member joined to the inner layer portion of the one terminal structure is connected to the terminal member joined to the outer layer portion of the other terminal structure. When joining terminal structures provided with terminal members for each layer in a conductor wound with a wire in n (n is an integer of 2 or more) layers, the terminal of the outermost layer (nth layer) in one terminal structure The member and the innermost layer (1
Layer) is connected to the terminal member. And sequentially, the (ni) th layer (i is an integer of 1 or more) in one terminal structure
And the terminal member of the (1 + i) th layer in the other terminal structure are connected. When the terminal member has an annular portion and a projection protruding from the annular portion, the terminal structures can be connected to each other by connecting the projections.

In the terminal structure of the present invention, the terminal members are joined to the outer layer and the inner layer, respectively. By adopting this structure, as will be specifically described below, the terminal processing steps are simplified, and the terminal processing can be performed mechanically. Further, if a terminal member surrounding the wire layer is used for the terminal treatment, the resistance value generated at the terminal part can be suppressed to a predetermined low level with good reproducibility.
This is because the resistance value generated at the terminal can be controlled to a low level by appropriately setting the size and material of the terminal member according to the structure and material of the conductor. Further, a terminal member is provided for each layer that is insulated from each other, and if an induced voltage based on a temporal change of a magnetic field generated by a current flowing through each terminal member is detected by a Rogowski coil, a distribution of a conduction current for each layer is obtained. be able to. This is very useful for knowing the characteristics of the conductor. In addition, if the terminal members are provided in each of the outer layer and the inner layer, the above-described connection method becomes possible. That is,
In connecting a pair of superconducting cable conductors, one outer layer and the other inner layer can be easily connected via a terminal member. By making such a connection, it is possible to suppress the drift phenomenon in which more current flows through the outer layer, and reduce the AC loss. Hereinafter, the present invention will be described in more detail with reference to specific examples.

[0019]

FIG. 1 shows a specific example of a terminal member used in the present invention. The terminal member 10 includes a cylindrical pipe portion 12 and a plate-shaped protrusion 14. The pipe portion 12 has two holes 16a and 16b. One of these functions as a hole for pouring the solder as described later, and the other functions as a hole for venting the air when the solder is poured. A plate-shaped protrusion 14 projects from the pipe 12 with a predetermined length. Projection 14
Is formed with a hole 18 for screwing. FIG. 2 shows a specific example of a process for performing terminal processing using a terminal member having such a shape.

For example, terminal processing is performed on a four-layer conductor as shown in FIG. First, as shown in FIG. 2A, a superconducting cable conductor 20 having the outermost superconducting wire 21d exposed on the surface is prepared. Next, all wires in the outermost layer (fourth layer) are removed by a predetermined length from the end of the conductor. After partially removing the insulating material covering the exposed third layer, the exposed third-layer wire is removed by a predetermined length from the end of the conductor, leaving a predetermined length. After partially removing the exposed insulating material, the exposed second-layer wire is partially removed. If the exposed insulating material is partially removed, the first-layer wire is exposed. Thus, FIG.
A step structure as shown in FIG. That is, a structure in which the inner layers are exposed toward the end of the conductor 20 is obtained. At the end of the conductor, the first-layer wire 21a is exposed, and the second-layer wire 21b and the third-layer wire 21c are sequentially exposed by a predetermined length. The wires of each layer are insulated by an insulating layer provided between the layers. Next, a terminal member having a structure as shown in FIG. 1 is attached to the wire of each layer. The material of the terminal member can be, for example, copper, but any other metal having a low resistance value can be used. In the structure as shown in FIG. 1, four terminal members are prepared in which the size of the pipe portion, particularly the inner diameter thereof is adjusted according to the diameter of each conductor layer, and attached to each layer. At the time of attachment, a conductor is inserted into the pipe portion of the terminal member and is arranged on a predetermined layer. Next, molten solder is poured from one of the two holes formed in the pipe portion to spread the solder between the pipe portion of the terminal member and the wire. The inner diameter of the pipe portion can be set to a value that is, for example, about 1 mm larger than the outer diameter of the conductor of each layer so that the solder flows as thinly and uniformly as possible. Further, the length of the pipe portion can be set to an appropriate value in consideration of the connection resistance and the like of the portion to be soldered. FIG. 2 shows a state in which terminal members are arranged on each layer and fixed by soldering.
It is shown in (c). Terminal members 10a, 10b, and 10 having appropriate sizes for the first, second, third, and fourth layers, respectively.
c and 10d are provided. Since each layer is electrically insulated by the insulating material, the terminal members provided in each layer are also electrically insulated.

By using the terminal member having the above-described structure, the terminal portion can be formed in a very simple process of merely inserting a conductor into the terminal member and pouring solder. Also, if a terminal member having an appropriate size is used and each layer is covered with this terminal member, a substantially uniform terminal resistance can always be obtained. Soldering is easy, and the resistance value due to the soldering layer has a small variation and can be suppressed to a certain low level. Therefore, the resistance value of the entire terminal unit can be suppressed to a certain low level. According to the present invention, for example, the resistance value of the terminal portion can be 1 μΩ or less per 50 m superconducting cable conductor. This resistance value is
This is such that it hardly affects the current distribution of the conductor.

In the terminal structure as shown in FIG. 2 (c), the terminal members are independently attached to each layer, so that the current flowing through each layer can be measured via each terminal member. The current value of each layer can be measured, for example, by attaching a Rogowski coil as shown in FIG. 3 to the projection of the terminal member. The Rogowski coil 30 can be configured by winding a copper wire 34 around a winding frame 32 made of, for example, fiber reinforced plastic (FRP). When measuring the conduction current of each layer,
A ring-shaped Rogowski coil may be inserted into the protrusions of the terminal members arranged on each layer.

When power is supplied from the power source to the conductor, the layers for the power supply can be collectively formed using, for example, a bus bar as shown in FIG. The bus bar 40 shown in the figure includes a connection plate 42 for connecting to terminal members attached to each layer, and a terminal portion 46 for attaching a lead connected to a power supply. In the connection plate 42,
Four screw holes 44a, 44b, 44c and 44
d are formed at predetermined intervals. The terminal portion 46 provided at the center of the lead plate 42 is also provided with a hole 48 for screwing the lead.

FIGS. 5 and 6 show a structure for attaching a Rogowski coil to each of the protrusions of the terminal members attached to each layer and supplying current to each layer collectively from the bus bar shown in FIG. Terminal members 10a, 10 joined to each layer
A Rogowski coil 30 is attached to each of the projections b, 10c and 10d. Each projection is joined to the connection plate 42 of the bus bar 40 by a screw 60. The material of the bus bar may be copper or another metal having a low resistance value. A current is supplied to each terminal via the terminal 46 of the bus bar 40. In addition, by adjusting the thickness of the projection of each terminal portion, it becomes easy to arrange each projection on the surface of the connection plate. The joined terminal members 10 a to 10 d and the bus bar 40 can be fixed on the support member 62. In such a terminal structure, the current value of each layer can be measured by calculating the current from the voltage induced in each Rogowski coil. Such a structure is important for knowing the characteristics of the conductor.

If the terminal structure shown in FIG. 2C is formed with respect to two conductors, the conductors can be connected by a structure as shown in FIGS. As shown in FIG.
The first layer terminal member 10a of one conductor is connected to the fourth layer terminal member 10'd of the other conductor.
Furthermore, the terminal member 10b of the second layer and the terminal member 1 of the third layer
0′c, the third-layer terminal member 10c and the second-layer terminal member 10′b are connected, and the fourth-layer terminal member 1
0d is connected to the terminal member 10'd of the first layer. The connection may be made by screwing as shown in the figure, or by another method, for example, brazing. By joining the projections of the terminal members, connection between the layers is facilitated. When connecting the protruding portions, as shown in FIG. 8A, the joining may be performed such that the annular portion is on the same side as the protruding portion.
As shown in (b), the joining may be performed such that the annular portions are opposite to each other with respect to the protruding portions. Further, if the connection is made as shown in FIG. 9, a more compact connection becomes possible. Further, as shown in FIG. 10A, terminal members having no protrusions can be joined by abutting each other.
Joining can be performed, for example, by brazing or the like. In this case, as shown in FIG. 10B, it is more preferable to use a ring-shaped terminal member having a flat portion to be joined. In general, current easily flows to the outer layer in a multi-layer conductor, but by connecting the outer layer and the inner layer in this way, it is possible to suppress the phenomenon of drift between conductors and prevent an increase in AC loss. Can be.

In the specific example described above, the terminal member is attached to each layer in the four-layer conductor, but depending on the case, a plurality of layers, for example, the first and second layers, the third and fourth layers, may be used. The terminal member may be attached to the combined second and third layers, and the like. However, even in this case, at least two terminal members are required for the inner layer and the outer layer.

[0027]

Example 1 Using a copper block having a shape as shown in FIG. 1, a 50 m long four-layer conductor was subjected to terminal treatment. The conductor was formed by spirally winding a tape-like wire rod in which a bismuth-based 2223 phase oxide superconductor was covered with silver around a former in four layers. The layers were insulated with Mylar tape. As shown in FIG. 2B, the wire at the end was removed in order from the outermost layer so that the surface of each layer was exposed by 13 cm. Next, as shown in FIG. 2C, a copper block was attached to each layer and soldering was performed. Specifically, a conductor was passed through the pipe portion of the copper block, the pipe portion was heated in a state where both ends of the pipe were sealed with heat-resistant tape, and molten solder was poured from one hole of the pipe portion. Immediately before the solder overflowed from the other hole, the pouring of the solder was stopped. The solder was solidified and a copper block was joined to each layer. By setting the inner diameter of the pipe portion in the copper block to the outer diameter of the conductor +1 mm for each layer, the solder could be poured smoothly, and the resistance of the terminal portion could be suppressed to a very small value of 1 μΩ or less. As a result of forming the same terminal structure a plurality of times, variation in the resistance value of the obtained terminal portion was small. In order to reduce the connection resistance, the length of the copper block was desirably about 10 cm.

A Rogowski coil was attached to the obtained terminal structure as shown in FIGS. The Rogowski coil is a ring sized to just pass the protrusions on the copper block. After attaching the Rogowski coil to the projection of each copper block, a copper bus bar as shown in FIG. 4 was further joined to the copper block of each layer by screwing. Thereby, each copper block was integrated. As shown in FIG. 6, the copper block and the copper busbar were fixed to a support made of FRP. Power was supplied by connecting a lead wire from a power supply to the terminal portion of the copper busbar. The output waveform of the voltage induced in each coil was recorded by an analyzing recorder. FIGS. 11A and 11B show the output waveforms from the coils and the current waveform obtained from the waveforms. From these figures, it became clear that the structure shown in FIGS. 5 and 6 could measure the current waveform of each layer. In addition, the analysis result of the conduction current waveform showed that the resistance value of the terminal portion was at a low level that did not substantially affect the conduction current waveform.

Example 2 As shown in FIG. 2C, two conductors having a terminal structure to which a copper block was attached were prepared. Then, FIGS. 7 and 8
The copper block was connected between the two conductors as shown in FIG. 1
When two wires were connected, the loss per unit length was reduced as compared with the conductor loss including the loss at the terminal when the wires were individually energized.

[0030]

As described above, according to the present invention, a terminal structure which can be formed by a simple process and has a low resistance value can be obtained. INDUSTRIAL APPLICABILITY The terminal structure of the present invention is suitable for measuring the current waveform of each layer, and can reduce the AC loss of a conductor even when two conductors are connected.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a specific example of a terminal member used in the present invention.

FIG. 2 is a schematic view showing one specific example of a process for manufacturing a terminal structure according to the present invention.

FIG. 3 is a perspective view showing a specific example of a Rogowski coil.

4A is a plan view and FIG. 4B is a side view showing a bus bar for supplying power connected to each terminal member.

FIG. 5 is a plan view showing a state where a Rogowski coil and a bus bar are attached to the terminal structure according to the present invention.

6 is a partial cross-sectional view of the structure shown in FIG.

FIG. 7 is a plan view showing a state where a pair of terminal structures are connected according to the present invention.

FIG. 8 is a side view showing a specific example of a state in which a pair of terminal structures are connected according to the present invention.

FIG. 9 is a side view showing another specific example of a structure in which a pair of terminal structures are connected according to the present invention.

FIG. 10 is a diagram showing another state in which a pair of terminal structures are connected according to the present invention;

FIG. 11 is a diagram showing (a) a coil output voltage waveform and (b) an energizing current waveform measured via each terminal member joined to each layer.

12A and 12B are a cross-sectional view and a side view schematically illustrating an example of a superconducting cable conductor.

[Explanation of symbols]

 10, 10a, 10b, 10c, 10d Terminal member 12 Pipe part 14 Projection part 20 Superconducting cable conductor 21a, 21b, 21c, 21d Superconducting wire 30 Rogowski coil 40 Busbar

Claims (11)

[Claims] 1. A terminal structure of a superconducting cable conductor having a structure in which a plurality of superconducting wires are wound around a core in a layered manner, wherein the outer layer of the plurality of wires has an outer layer on the surface. A terminal member provided around the outer layer portion and joined to a wire material in the outer layer portion; and the wire material in the inner layer without the wire material in the outer layer of the plurality of wire materials is exposed. An inner layer portion, comprising a terminal member provided around the inner layer portion and joined to a wire rod in the inner layer portion,
Terminal structure of superconducting cable conductor. 2. The wire rods of each layer are selectively exposed in order from the outermost wire rod to the innermost wire rod toward the end of the cable conductor. The terminal structure according to claim 1, wherein the terminal member is joined. 3. The terminal structure according to claim 1, wherein the terminal members are electrically insulated from each other by an insulating material between the outer layer and the inner layer. 4. The terminal member according to claim 1, wherein said terminal member has an annular portion surrounding said wire layer and a projection projecting from said annular portion. Terminal structure. 5. The terminal structure according to claim 4, wherein a Rogowski coil can be inserted into the protrusion. 6. The terminal member having the annular portion and the protrusion is provided for each layer of the wire, and a Rogowski coil is inserted into the protrusion of each terminal member, so that a current flowing through each layer is provided. The terminal structure according to claim 4, wherein a distribution can be detected. 7. The terminal member according to claim 1, wherein the terminal member is joined to the wire member by solder poured between the layer of the wire member and the terminal member provided therearound. The terminal structure according to any one of claims 1 to 6. 8. The terminal structure according to claim 7, wherein the terminal member has a hole into which the solder is poured. 9. The terminal structure according to claim 1, wherein the resistance value is 1 μΩ or less. 10. The superconducting wire is made of bismuth-based 222.
The terminal structure according to any one of claims 1 to 9, wherein the terminal structure is a tape-shaped wire including a three-phase oxide superconductor and a stabilizing matrix covering the three-phase oxide superconductor. 11. A method for electrically connecting a pair of terminal structures according to any one of claims 1 to 10, further comprising: a terminal member joined to the outer layer portion in one terminal structure. A terminal member connected to the inner layer portion in the other terminal structure and a terminal member bonded to the inner layer portion in the one terminal structure and a terminal member bonded to the outer layer portion in the other terminal structure. And a connection method for a terminal structure.