JPH0512931A - Superconducting wire - Google Patents

Abstract

PURPOSE:To improve the current capacity in a superconducting wire for alternating current by reducing an AC loss in the superconducting wire and moreover enhancing the cooling efficiency. CONSTITUTION:The superconducting wire is constituted as a primary stranded wire such that superconducting element wires 13, in which superconducting filaments being embeded in a matrix, are stranded about a primary stranding center wire 15, the primary stranding center wire 15 is constituted by embeding a stabilizing material 17 in a matrix 16. The stabilizing material is constituted as a secondary stranded wire such that the primary stranded wire 10 being stranded about a secondary stranding center wire. Furthermore, the secondary stranded wire is constituted as a tertiary stranded wire such that it is stranded with a spacer about a tertiary stranding center wire. The increase in a bond current between superconducting filaments reduces an AC loss, furthermore the reduction in self magnetic field and the improvement in a cooling efficiency enhances the current capacity in a superconducting wire.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting wire, and more particularly to an AC superconducting wire.

[0002]

2. Description of the Related Art Metal-based superconducting wires made of NbTi have come to be widely used in superconducting coils for magnetic levitation trains and magnetic resonance tomography apparatuses (MRI) at present. When applied to alternating current rather than direct current such as 50 or 6 such as commercial frequency, the frequency is not a few hertz like pulse current.
In the case of 0 Hz, how to reduce the AC loss due to the fluctuating magnetic field is the key to the practical application of the AC superconducting wire.

As is well known, there are three types of AC loss: hysteresis loss, coupling loss and eddy current loss. In the prior art, various measures have been taken to reduce such AC loss.

Hysteresis loss is the work of pinning force in a superconducting filament with respect to a fluctuating magnetic field. This amount is proportional to the diameter of the filament and the magnitude of the fluctuating magnetic field. In addition, the hysteresis loss is reduced by making the submicron order even thinner.

The coupling loss is a loss due to a current flowing in a loop shape between filaments, and this amount is proportional to the time change rate of the magnetic field and the square of the twist pitch of the filaments, that is, between the filaments, that is, in the wire rod. Since it is inversely proportional to the specific resistance in the orthogonal direction, the twist pitch is twisted to the limit of the material, and CuNi having a large specific resistance is put between the filaments to reduce the coupling loss.

Further, the eddy current loss is the loss due to the eddy current generated in the stabilizing material having a small specific resistance arranged in the wire direction in order to prevent quenching. It is proportional to the square of the diameter of the eddy current and inversely proportional to the specific resistance of the stabilizing material. For this reason, CuNi with a large specific resistance is arranged in the wire direction, and the stabilizer is finely divided in parallel to the wire direction to reduce the diameter of the eddy current, thereby stabilizing the stabilizer in order to avoid quenching. The eddy current loss is reduced while allowing the electric current to flow through.

[0007]

[Problems to be Solved by the Invention]
FIG. 5 shows an AC superconducting wire 1 of Japanese Patent Application No. 3-120376 filed on May 24, 2013. This superconducting wire 1
Is a NbTi microfilament 2 and a CuNi matrix 3
7 pieces of superconducting element wires 5 each having a Cu 4 as a stabilizing material arranged in the vicinity of the center are combined. In this superconducting wire 1, since the filament 2 is made extremely thin, hysteresis loss can be reduced, and in addition, as shown in FIG.
As can be seen in, since Cu as a stabilizing material is finely divided and put, eddy current loss can be reduced. Further, since the filament 2 is embedded in the CuNi matrix 3 and the superconducting element wire 5 is twisted, the coupling loss can be reduced to some extent.

However, in such a superconducting wire 1, since the coupling current flowing between the filaments 2 flows in the diameter direction of the superconducting element wire 5 and crosses the central portion, not only the CuNi matrix 3 having a large specific resistance but It also flows into Cu4, which has a low resistance, causing considerable coupling loss.

Further, since the superconducting filament 2 for AC has a small filament diameter, the superconducting element wire 5 is also thin, and the current capacity of the superconducting element wire 5 is, for example, about 20A. For this reason, it is necessary to put the AC superconducting wire 1 shown in FIG. 5 into a large current capacity of about several thousand amps for practical use. As shown in FIG. 6, such a superconducting stranded wire has a structure in which the superconducting wire 1 shown in FIG. 5 is used as a primary stranded wire, and the primary stranded wire 1 is insulated from the stainless steel wire 6 by, for example, 6 strands. A secondary stranded wire 7 is also formed, and the secondary stranded wire 7 is combined with, for example, six stainless steel wires 8 having a large diameter and subjected to an insulation treatment to form a tertiary stranded wire 9.

In such a tertiary twisted wire 9, since the secondary twisted wires 7 are close to each other, the so-called self-magnetic field generated in each secondary twisted wire 7 itself is influenced by other secondary twisted wires 7. It gets bigger and bigger. As described above, since each AC loss depends on the magnitude of the magnetic field or its rate of change over time, the actual AC loss of the tertiary twisted wire 9 is predicted from the loss when the secondary twisted wire 7 is used alone. It is much larger than the loss of the third stranded wire 9 that is generated. In addition to this, since the secondary twisted wires 7 are close to each other, the amount of heat generated per unit cross-sectional area is increased and the cooling efficiency is reduced, so that the current capacity of the tertiary twisted wires 9 is further reduced.

The present invention has been made in consideration of the above-mentioned circumstances, and prevents damage due to Joule heat generation when the superconducting portion is changed to the normal conducting state, and at the same time reduces the AC loss during normal energization. The purpose is to provide a wire rod.

Furthermore, the present invention provides a superconducting wire for alternating current with a large current capacity by providing a structure having a small AC loss and a high cooling efficiency when the superconducting wire for alternating current is twisted together. To aim.

[0013]

[Means for Solving the Problems] The above-mentioned problem is that a superconducting filament is embedded in a matrix to form a superconducting element wire, and this superconducting element wire is aligned around a center wire material in which a stabilizing material is embedded in a matrix, The problem is solved by providing a superconducting wire having a stranded wire.

Further, the above-mentioned problems can be solved by providing a superconducting wire comprising a superconducting wire in which a superconducting filament and a stabilizing material are embedded in a matrix and which are alternately aligned around a center wire together with a spacer.

[0015]

With the structure according to the first aspect, it is possible to reduce the AC loss during normal energization and prevent damage due to Joule heat generation when the superconducting portion changes to the normal conducting state.

Further, according to the structure described in claim 3,
It is possible to reduce the AC loss of the superconducting wire and increase the cooling efficiency to increase the current capacity of the superconducting wire.

[0017]

Embodiments of the superconducting wire according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a schematic configuration example of a superconducting wire according to the present invention.

This superconducting wire 10 comprises a superconducting element wire 13 in which a superconducting filament 12 is put in a CuNi matrix 11.
Is a primary twisted wire composed of, for example, six twisted wires around the primary twisted center wire 15. The primary twist center wire 15 is 1
It is arranged in the center of the next twisted wire 10, and is constructed by inserting Cu 17 into a CuNi matrix 16. As can be seen in FIG. 1, the superconducting wire 13 is twisted around the primary twist center wire 15 in order to reduce the coupling loss. The superconducting filament 12 is preferably made of NbTi alloy, but Nb ₃ Sn
It may be a superconducting filament such as. Further, the number of twists may be another number depending on the diameter of the strands or the center wire of the strands, the current capacity of the strands, and the like.

Further, the primary twisted wire 10 shown in FIG.
As shown in, a superconducting wire rod 20 may be formed around the secondary twisted central wire rod 18 by, for example, six twisted secondary twisted wires.

The secondary twisted center wire 18 is preferably made of a material having a large specific resistance and non-magnetism and can be easily bent when the coil is wound. However, due to the above-mentioned twist structure, the coil is energized. The electromagnetic force that sometimes occurs is almost 2
It acts on the next twist center wire 18. Therefore, stainless steel 21 having high structural strength is most preferable. Further, in order to avoid unnecessary inflow of current into the stainless steel, it is preferable to provide an insulating coating 22 such as formal insulation.

Next, the operation of the superconducting wires 10 and 20 will be described.

Since the superconducting element wire 13 is twisted, the coupling loss is reduced. However, in the present embodiment, the superconducting filament 12 is further embedded in the CuNi matrix 11 having a large specific resistance, and the superconducting filament 12 has a relatively high resistance. Since Cu with low resistance is not present, the coupling current induced in the loop formed between the superconducting filaments by the varying magnetic field is reduced. Therefore, it is possible to effectively reduce the coupling loss during AC energization.

Further, as shown in FIG. 3 (a), normally, almost no voltage is generated in the superconducting wire 13, so that the current flowing through the superconducting wire 13 does not flow into the primary twist center wire 15. However, as shown in Fig. 3 (b), when the superconducting element wire 13 changes to normal conducting for some reason, the current flowing through the superconducting element wire 13 is due to the voltage generated at the normal conducting transition part. , The CuNi matrix 16 of the primary twist center wire 15 through the contact point between the superconducting wire 13 and the primary twist center wire 15.
Since it passes through and further flows into Cu 17, it is possible to prevent Joule heat generation due to the current flowing to the normal conduction transition portion. The normal-conducting part where the current has stopped flowing becomes below the critical temperature after a certain time due to the cooling action of liquid helium (not shown), and the normal-conducting part returns to the superconducting state and the current flows through the superconducting element wire 13 as before. Like

Next, a second embodiment of the superconducting wire according to the present invention will be described.

FIG. 4 shows an example of a schematic structure of a superconducting wire 30 as a superconducting stranded wire of the present invention.

This superconducting wire 30 is made by combining the superconducting element wire 13 around the primary twist center wire 15 with, for example, six wires.
A secondary twisted wire 20 is formed by combining, for example, six secondary twisted wires 10 around the secondary twisted center wire material 18, and the secondary twisted wire 20 as the superconducting wire is wound around the third twisted center wire material 31. Together with the spacer 32, for example, twist 6 pieces each
The next twisted wire 30 is used.

The superconducting wire 13 is made of CuNi matrix and Nb.
1 is a superconducting element wire of a first embodiment of the present invention shown in FIG. 1 in which a superconducting filament such as Ti or Nb ₃ Sn is embedded, and a primary twist center wire 15 is a primary twist center wire similarly shown in FIG. It is better to correspond to No. 15, but the superconducting element wire 13 is a superconducting element wire as shown in FIG. 5 in which a stabilizing material is embedded in the superconducting element wire. May be

Secondary twist center wire 18, Third twist center wire 31
The spacer 32 has a large specific resistance, is a non-magnetic material, and has an appropriate elasticity so that the coil can be easily manufactured, and a formal-insulated stainless wire is most preferable. Further, in order to facilitate winding at the time of manufacturing the coil, it is preferable that the tertiary twist center wire rod 31 is divided into a plurality of wires to reduce the bending rigidity of the whole center wire rod.

Next, the operation of this superconducting wire 30 will be described.

Since the secondary twisted wires 20 are separated from each other by the spacer 32, the distance between the secondary twisted wires becomes large. Therefore, the magnetic field strength exerted by each secondary twisted wire 20 on the other secondary twisted wires 20 is reduced, and the self-magnetic field is reduced. Therefore, since the hysteresis loss generated in the superconducting filament, the coupling loss due to the coupling current flowing between the superconducting filaments, and the eddy current loss flowing in the stabilizing material are reduced respectively,
AC loss generated in the entire superconducting wire 30 can be effectively reduced. Further, since the secondary twisted wires 20 are dispersed and arranged by the spacers 32, the generated Joule heat can be efficiently cooled.

By reducing the AC loss and improving the cooling efficiency, the current capacity of the superconducting wire 30 is greatly improved.

In the second embodiment, the case where the secondary stranded wire is the superconducting wire and the tertiary stranded wire is the superconducting stranded wire has been described. However, the primary stranded wire is the superconducting wire and this is the center wire. The secondary stranded wire that is alternately aligned with the spacer around the superconducting stranded wire may be used as the superconducting stranded wire. It may be a line.

In the embodiments of the present invention, the superconducting wire is used for alternating current, but the present invention is not limited to this and may be used for direct current.

[0035]

EFFECT OF THE INVENTION A superconducting wire made up of a primary stranded wire in which a superconducting element wire in which a superconducting filament is embedded in a matrix is matched around a central wire material in which a stabilizing material is embedded in a matrix, and stabilization for preventing quenching is achieved. While doing so, it is possible to reduce the AC loss of the superconducting wire.

Further, the AC loss of the superconducting wire can be reduced by using the superconducting wire consisting of twisted wires in which the superconducting filament and the stabilizing material are embedded in a matrix and are alternately arranged around the center wire together with the spacer. Moreover, since the cooling efficiency can be improved, the current capacity of the superconducting wire can be increased.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a primary twisted wire according to an embodiment of the present invention.

FIG. 2 is a view in which the primary stranded wire shown in FIG.
Schematic sectional view of the next twisted wire.

FIG. 3 (a) is an explanatory diagram showing how current flows in a normal state,
(b) is an explanatory view showing how the current flows when the superconducting portion is changed to the normal conducting state.

FIG. 4 is a view of a structure formed by twisting the secondary twisted wires shown in FIG.
Schematic sectional view of the next twisted wire.

FIG. 5: Japanese Patent Application No. 3-1203 filed by the applicant
The schematic sectional drawing of the superconducting wire of No. 76.

FIG. 6 is a schematic cross section of a tertiary twisted wire in which the primary twisted wire shown in FIG. 5 is wound around a stainless steel wire to form a secondary twisted wire, and the secondary twisted wire is wound around a stainless steel wire having a large diameter. Fig.

[Explanation of symbols]

1 Primary stranded wire 2 Superconducting filament 3 matrix 4 Stabilizer 5 Superconducting wires 6 Secondary twist center line 7 Secondary stranded wire 8 Third twist center wire 9 Third strand 10 Primary stranded wire 11 matrix 12 Superconducting filament 13 Superconducting wires 15 Primary center wire 16 matrix 17 Stabilizer 18 Secondary center wire 20 Secondary stranded wire 21 stainless steel 30 Third stranded wire 31 Third twist center wire 32 spacer

Claims (4)

[Claims] 1. A primary stranded wire is formed by embedding a superconducting filament in a matrix to form a superconducting element wire, and combining the superconducting element wire around a center wire material having a stabilizing material embedded in the matrix. Superconducting wire rod. 2. A superconducting element wire is formed by embedding a superconducting filament in a matrix, and the superconducting element wire is combined around a center wire material having a stabilizing material embedded in the matrix to form a primary twisted wire. A superconducting wire, characterized in that a secondary twisted wire is formed by combining the next twisted wire around the center wire. 3. A superconducting wire comprising a superconducting wire in which a superconducting filament and a stabilizing material are embedded in a matrix, and the superconducting stranded wire is alternately arranged around a center wire together with a spacer. 4. The matrix is made of CuNi,
4. The superconducting filament is made of an NbTi alloy, the stabilizer is made of Cu, and the center wire and the spacer are formal-insulated stainless wires. The described superconducting wire.