JPH07111112A - Slow-response nbti superconductor - Google Patents

Abstract

PURPOSE:To clarify the relation between predetermined parameters of fabrication requirements and the stability of a conductor so as to enhance stability by setting data of superconducting wire to predetermined values. CONSTITUTION:A low-response NbTi superconductor 1 is a rectangular swaged stranded cable comprising NbTi/CuCuNi three-layered superconducting wires 2 twisted together. Each of the superconducting wires 2 comprises a stabilizing Cu layer 3, an NbTi-filament-bundle 5 formed around the layer 3, a 10wt.%-Cu Ni layer 6 formed around the bundle 5, a stabilizing Cu layer 7 formed around the layer 6, and a 10wt.%-Cu Ni layer 8 formed around the layer 7. The bundle 5 comprises NbTi filaments 10 embedded in a matrix 11 of 10wt.%-Cu Ni, with Cu 9 disposed around each of the filaments 10. The effective Cu ratio of each of the wires 2 is 1.6 or more, the thickness of the layer 6 is 10mum or less, the twisting pitch of the wires 2 is nine to twelve times the diameter of each wire 2, and the void ratio of the conductor 1 is 13 to 15%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low speed response type NbTi superconducting conductor, and more particularly to a low speed response type NbTi superconducting conductor used in electric power application fields such as a superconducting generator.

[0002]

2. Description of the Related Art The NbTi conductor used for the field winding of a low speed excitation type superconducting generator is required to have an optimum conductor with high stability and high current density. For example, the basic specifications of a 70,000 kW class low-speed generator and the required characteristics of conductors applied to field windings are shown in Tables 1 and 2 below.

[0003]

[Table 1]

[0004]

[Table 2]

Conventionally, the production of a conductor in accordance with this has been studied, but no conductor satisfying the required characteristics has existed.

[0006]

These conductors that have been studied in the past were flat-molded single stranded wires using NbTi / Cu / CuNi three-layer structure superconducting wires. The wire diameter was 1.6 mm, Cu was arranged around a NbTi filament system of about 9 μm, and embedded in a single stack in a matrix of Cu-10 wt% Ni. As for the cross-sectional structure, the stability was emphasized and the stabilized Cu was arranged inside and outside the filament bundle portion to improve the stability.

However, these conductors, which have been studied so far, have a problem of poor stability. The stability of the conductor defined here means that the training to reach Ic is small when the critical current (Ic) of the conductor is measured, and that the conductor Ic reaches the number of twists of the strand Ic several times. Therefore, if the conductor is trained many times, a large amount of liquid helium will be consumed to obtain the operating current of the conductor during the initial operation of the generator.
There was a problem that the operating cost would be huge. Further, if the number of twists of the strand Ic is not reached, there is a problem that the performance of the designed generator cannot be exhibited.

Conventionally, such a problem of stability is caused by setting a complicated strand wire cross-section structure and conductor cross-section structure in order to satisfy each characteristic of the conductor (critical current, AC loss, residual resistance ratio, etc.). It was due to being there. Moreover, there are many parameters of the manufacturing conditions, and the relationship between the set values of these parameters and the stability of the conductor is unknown.

An object of the present invention is to clarify the relationship between the set values of these parameters and the stability of the conductor, and to provide a low-speed response type NbTi superconducting conductor having excellent stability.

[0010]

A low-speed response type NbTi superconducting conductor according to the present invention is a NbTi composed of a rectangular shaped twisted wire using a NbTi / Cu / CuNi three-layer structure superconducting wire.
A superconducting conductor, wherein the superconducting element wire is a first stabilized Cu.
Layer and a first C formed around the first stabilizing Cu layer
u-10 wt% Ni layer and first Cu-10 wt% Ni layer
A NbTi filament bundle portion formed around the layer, a second Cu-10 wt% Ni layer formed around the NbTi filament bundle portion, and a second Cu-10
A second stabilizing Cu layer formed around the wt% Ni layer and a third Cu formed around the second stabilizing Cu layer
-10 wt% Ni layer, the NbTi filament bundle part has a structure in which NbTi filaments around which Cu is arranged are embedded in a matrix of Cu-10 wt% Ni, and the effective Cu ratio of the superconducting wire is Is 1.6 or more, and the thickness of the second Cu-10 wt% Ni layer is 10 or more.
μm or less, the twist pitch when twisting the superconducting element wire is 9 times or more and 12 times or less the diameter of the superconducting element wire, and the void ratio of the superconducting conductor is 13% or more and 15% or less.

Here, the effective Cu ratio of the superconducting element wire is N
It is the ratio of bTi and stabilized Cu (the sum of the first stabilized Cu and the second stabilized Cu, excluding the stabilized Cu around the NbTi filament).

[0012]

The present inventors extracted the difference between the trial-produced conductors in order to identify the factors affecting the stability, and examined the results by characteristic factors. As a result, it was found that the electrical and thermal characteristic factors affect the stability. We obtained the finding that it is an interaction between the and mechanical characteristic factors. Here, the electrical and thermal characteristic factor means a decrease in stability due to an increase in the CuNi barrier thickness for reducing AC loss in the wire, a decrease in the effective Cu ratio, and the like. On the other hand, the mechanical characteristic factor means an increase in the easiness of movement of the conductor due to an increase in rigidity due to the reduction of the void ratio and the twist pitch.

Furthermore, the present inventors have made clear that, in factors (twist pitch, void ratio, etc.) that are considered to determine the mechanical properties of the conductor, the bending elastic modulus can be considered as a guideline among the mechanical properties. It was shown quantitatively that the bending elastic modulus was larger as the void ratio of the conductor was smaller, and was larger as the twist pitch of the wire was shorter. From this result, it was clarified that the rigidity of the conductor is related to the stability.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view showing the structure of an example of a low-speed response type NbTi superconducting conductor.

Referring to FIG. 1, this low-speed-response NbTi superconducting conductor 1 is a flat-shaped molded stranded wire formed by twisting NbTi / Cu / CuNi triple-layer superconducting wires 2.

The superconducting wire 2 has a first stabilizing Cu layer 3
And the first Cu-10 wt% Ni formed around it
Layer 4, NbTi filament bundle part 5 formed around it, and second Cu-10 formed around it
wt% Ni layer 6, second stabilizing Cu layer 7 formed around it, and third Cu-10w formed around it
and a t% Ni layer 8.

Further, the NbTi filament bundle portion 5
Is an NbTi filament 1 with Cu9 arranged around it.
0 is embedded in a matrix 11 of Cu-10 wt% Ni. (Experimental Example) Three kinds of conductors having the specifications shown in Table 3 were constructed as shown in FIG.

The conductor (A) is an embodiment of the present invention,
It was manufactured so as to satisfy the required characteristics shown in Table 2. For comparison, the conductor (B) has a conductor configuration that balances the critical current and the residual resistance ratio (RRR) while reducing the AC loss by reducing the twist pitch from the conductor (A). For comparison, the conductor (C) also has a significantly improved critical current and residual resistance ratio (RRR) from the conductor (B), and uses a wire with a reduced twist pitch, and is a full conductor void. Rate reduction (14% of conventional)
It is a conductor designed for compaction by reducing from the stand to 12%).

[0019]

[Table 3]

Comparing the three types of conductor characteristics obtained in this way, the conductor (A) is stable (less training is required to reach Ic when measuring the Ic of the conductor, and the conductor Ic is the same as that of the wire Ic). It is clear from the test results that it is favorable in terms of reaching the number of twists several times). On the other hand, the conductor (B) and the conductor (C) improved by optimizing the critical current and the AC loss have a test result that the stability of the conductor is poor.

From these facts, as described above, the difference in conductors was extracted in order to extract the factors affecting the stability, and the results were sorted and examined according to the characteristic factors. As a result, it is the electrical factors that affect the stability. It was found that it is an interaction between thermal characteristic factors and mechanical characteristic factors. Here, the electrical and thermal factors mean a decrease in stability due to an increase in the CuNi barrier thickness for reducing the AC loss in the wire and a decrease in the effective Cu ratio. Further, the mechanical characteristic factor means an increase in the easiness of movement of the conductor due to an increase in rigidity due to the reduction of the void ratio and the twist pitch.

These concrete results are shown in Tables 4 and 5.
Shown in.

[0023]

[Table 4]

[0024]

[Table 5]

Referring to Table 4, the electrical and thermal factors are CuNi that partitions the NbTi filament bundle portion.
The thickness of the barrier is 10 μm in the conductor (A), whereas it is 20 μm or more in both the conductor (B) and the conductor (C). Therefore, the AC loss shows a small value in the conductor (B) and the conductor (C), but it was found that this setting is a factor that deteriorates the stability. Furthermore, NbTi and NbT
Ratio with stabilized Cu excluding around i-filament (effective C
It was also found that the u ratio) also contributed to the stability. From the results shown in Table 4, this effective Cu ratio needs to be 1.6 or more. On the other hand, the residual resistance ratio (RRR) and the critical current density (Jc), which were conventionally considered to affect the stability, did not show a clear correlation with the stability.

With reference to Table 5, it was found that as mechanical factors, the twist pitch of the wire and the void ratio of the conductor contribute to the stability of the conductor. Twist pitch is 16mm
Stability is good when (10 times the wire diameter), and 12.5
In the case of mm (7.8 times the wire diameter), the stability deteriorated. Therefore, it was clarified that a twist pitch of about 10 times the wire diameter is good. It was also found that it is preferable that the twist direction and the twisted wire direction are the same.

Next, in order to experimentally examine specific numerical values of factors (twist pitch, void ratio) that are considered to determine the mechanical properties of the conductor, the conductors shown in Table 6 were prepared and tested. went.

[0028]

[Table 6]

With respect to the conductor thus obtained, the bending elastic modulus as a representative of the mechanical properties and the correlation between these parameters were arranged with the conductor (A) as 1. The results are shown in FIGS. 2 and 3.

FIG. 2 is a diagram showing the relationship between the void fraction (%) and the bending elastic modulus (kg / mm ² ).

FIG. 3 is a diagram showing the relationship between the twist pitch (mm) and the bending elastic modulus (kg / mm ² ).

With reference to FIGS. 2 and 3, it has been found that the bending elastic modulus increases as the void ratio of the conductor decreases, and increases as the twist pitch of the wire decreases. In particular,
It was found that the twist pitch is preferably 9 to 12 times the wire diameter and the void ratio is 13 to 15%.

[0033]

As described above, according to the present invention, a low-speed response type NbTi superconducting conductor having excellent stability can be obtained.

Therefore, the low-speed response type Nb according to the present invention
The Ti superconducting conductor requires less training to reach Ic when the critical current (Ic) of the conductor is measured, and the conductor Ic can reach the number of twists of the strand Ic.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of an example of a low-speed response type NbTi superconducting conductor.

FIG. 2 is a diagram showing a relationship between a void fraction and a bending elastic modulus.

FIG. 3 is a diagram showing a relationship between a twist pitch and a bending elastic modulus.

[Explanation of symbols]

 1 Slow response type NbTi superconducting conductor 2 NbTi / Cu / CuNi three-layer structure superconducting element wire 3 First stabilizing Cu layer 4 First Cu-10 wt% Ni layer 5 NbTi filament bundle part 6 Second Cu-10 wt% Ni Layer 7 Second stabilizing Cu layer 8 Third Cu-10 wt% Ni layer 9 Cu 10 NbTi filament 11 Cu-10 wt% Ni matrix

Claims (1)

[Claims] 1. A NbTi superconducting conductor comprising a flat-shaped molded stranded wire using a NbTi / Cu / CuNi three-layer structure superconducting element wire, wherein the superconducting element wire comprises a first stabilizing Cu layer and the first stabilizing Cu layer. First Cu formed around the stabilized Cu layer of
A -10 wt% Ni layer, an NbTi filament bundle portion formed around the first Cu-10 wt% Ni layer, and a second Cu-10 wt% Ni layer formed around the NbTi filament bundle portion. A second stabilized Cu layer formed around the second Cu-10 wt% Ni layer, and a third Cu formed around the second stabilized Cu layer
-10 wt% Ni layer, and in the NbTi filament bundle portion, NbTi filaments around which Cu is arranged are Cu-10 wt% Ni.
Of the superconducting element wire, the effective Cu ratio of the superconducting element wire is 1.6 or more, and the thickness of the second Cu-10 wt% Ni layer is 10 μm or less. A low-speed response type NbTi superconducting conductor, wherein a twist pitch when twisting the strands is 9 times or more and 12 times or less of the diameter of the superconducting element wire, and a void ratio of the superconducting conductor is 13% or more and 15% or less.