JP3145173B2 - Superconducting stranded wire and superconducting cable, and power equipment winding using them - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting stranded wire formed of a superconductor, a superconducting cable, and an improvement in a winding of a power device using the same. More specifically, the present invention relates to a superconducting stranded wire, a superconducting cable, and an improvement in a critical current of a power device winding using the same.

[0002]

2. Description of the Related Art In recent years, a large number of superconducting stranded wires obtained by bundling and twisting a large number of superconductor strands have been developed as large-capacity superconductors. Also, a number of superconducting twisted wires are bundled to form a sub-cable, and a number of superconducting cables using a plurality of such sub-cables have been developed. Also, development of superconducting power devices using these superconducting stranded wires and superconducting cables has been very active.

[0003]

However, when current is actually applied to these conventional superconducting stranded wires and superconducting cables and used, the current of each strand and each sub-cable of the stranded wires is unbalanced due to the imbalance in inductance. And a critical current does not flow by the number of wires and sub-cables, which is regarded as a problem.

[0004] This problem will be described in more detail with reference to a superconducting stranded wire shown in FIG. For example, when the superconducting stranded wire S formed by the _seven strands S _{1 to} S ₇ is arranged with the other strands S _{1 to} S ₆ so as to surround the strand S ₇ , the strand S ₁ ~
Difference between the current i _a flowing in the current i and the wire S ₇ flowing to S ₆ has been found to occur. That is, it has been found that a critical current that is several times as large as that of the strands causes a degradation that does not flow through the superconducting stranded wire S.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a superconducting stranded wire, a superconducting cable, and a power device winding utilizing the same, which make the critical current flowing through each element wire and each sub-cable uniform and improve the critical current.

[0006]

In order to achieve the above object, a superconducting twisted wire or superconducting cable according to the present invention is provided with a current control means for controlling current for each strand or sub-cable.

Further, in the superconducting stranded wire or superconducting cable of the present invention, the strands of the wires are partially widened to increase the distance between the wires or to partially widen the space between the sub-cables. .

Further, a power device winding according to the present invention is characterized in that a power device is wired using the above-described superconducting stranded wire or superconducting cable.

[0009]

Therefore, the current flowing through each element wire is controlled by the current control means to make it uniform. In other words, the phase difference between the outer strand and the center strand is controlled to make the current flowing through the strand uniform.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of the present invention will be described below in detail with reference to the embodiments shown in FIGS.

FIG. 1 shows an embodiment of a superconducting stranded wire according to the present invention. This superconducting stranded wire is formed by twisting two or more superconducting wires S _{1 to} S ₇ together with the wires S _{1 to} S _7.
Made by adding the current control means such as series impedance z ₁ to z ₇ performs current control for each.

First, the current flowing through each strand will be analyzed based on FIGS. In general, the self and mutual inductances of a parallel two-wire conductor when a current flows uniformly in each strand are given by the following equations (1) and (2).

[0013]

(Equation 1)

[0014]

(Equation 2) Here, n is the length of the conductor, a is the conductor radius, d is the distance between the conductors, the L _w and M _w is L _w = M _w in the self inductance and mutual inductance due to the wound coil. Although the effects of twist and twist are ignored in Equations 1 and 2, the validity of this assumption has been verified.

Each of the strands S _{1 to} S ₇ of this embodiment is formed by a known or new superconducting member. A circuit equation of a seven-stranded wire is established by Expressions 1 and 2. 7
The outer strand S ₁ surrounding the strand S ₇ in the main strand S
For six to S ₆ inductance are equal, the critical current which flows are considered equal. The critical current that flows to the outside of the strand S ₁ ~S ₆ i _o, the critical current that flows through the center strand S ₇ and i _i, when the voltage across the v, so Equation 3.

[0016]

(Equation 3) Here, z is impedance z ₁ ~z _7, M ₁ shown in FIG. 2, which is connected in series to Kakumotosen S ₁ to S ₇ are wire S ₁
A mutual inductance between so Tonaria' were strands of wire S _2, M ₂ is the mutual inductance between the strands of the positional relationship as the strand S ₁ and strand S _3, M ₃ is wire S ₁ mutual inductance, L between sandwiching strands the center strand S ₇ as wire S ₄ is a self-inductance of Kakumotosen S ₁ to S _7. For simplicity of calculation, the impedance z ₁ to z ₇ connected to each wire S ₁ to S ₇ are all equal. From Equation 3, the following Equation 4 is obtained.

[0017]

(Equation 4) By substituting Equations 1 and 2 into this,

[0018]

(Equation 5) Becomes Here, d ₁ , d ₂ , and d ₃ are distances between the strands S _{1 to} S ₂ , S _{1 to} S ₃ , and S _{1 to} S ₄ , respectively, and d ₂ = √3 · d ₁ , d ₃ = is 2d _1. Substituting these gives

[0019]

(Equation 6) Next, let the impedance per unit length be z _0, that is, z ₀ = z / n, and rationalize:

[0020]

(Equation 7) Becomes According to Equation 7, the critical current ratio i _i / i _o between the outer strands S _{1 to} S ₆ and the central strand S ₇ is represented by the impedance z ₀ per unit length and the ratio of the conductor spacing to the conductor radius. It can be seen that d ₁ / a is a function of the frequency f.

Here, as a parameter of the seven-stranded wire S, the distance d ₁ between the strands S _{1 and} S ₂ in this embodiment is equal to:
0.14 mm, conductor radius a = 0.06 mm, frequency f =
Substituting 50Hz gives

[0022]

(Equation 8) Becomes According to Equation 8, when there is no series impedance, that is, when z ₀ = 0, the imaginary part becomes zero and i _i
/ A i _o = -0.633. This is the central strand S ₇
Is 180 ° out of phase with the current i _o flowing through the outer six strands S _{1 to} S ₆ , indicating that the total transport current It is _equal to the outer strand S ₁ to
When the current flowing to the S ₆ reaches I _c,

[0023]

(Equation 9) Next, indicates that not flowing strands present several times the current of I _c. Also from Equation 8, the current i _o and the center of the strand S ₇ of the increases the z ₀ outside wires S ₁ to S ₆
The currents i _i whose phases are shifted by 180 ° gradually become more uniform.

That is, as shown in FIG. 1, by adding a somewhat large series impedance z _{1 to} z ₇ to each of the strands S _{1 to} S ₇ , the current i _i of the central strand S ₇ is reduced to the outside strand. The currents i _o of the lines S _{1 to} S _{6 have} the same phase as that of the currents i _o, and the degradation due to the non-uniform current distribution can be suppressed. That is, in the case of this embodiment, the series impedance z ₁ to z ₇ is a current control means.

FIG. 2 shows another embodiment of the present invention. This example extends the twist at any position in the middle of the strand S ₁ to S ₇ as shown in FIG. 2, the provision of the spacing between the wires S ₁ to S _7, i.e. the wires S ₁ by a large distance between the to S ₇ can positively the real part of the current ratio of equation 7, it is possible without adding a series impedance to eliminate the degradation. In Equation 7, z ₀ =
Substituting 0, f = 50Hz gives

[0026]

(Equation 10) And i _i / i _o = 0 when d ₁ /a=4.673
That is, the current i _i flowing through the central element wire S ₇ becomes 0, and d ₁
When /a>4.673, i _i / i _o > 0, d ₁ / a →
In the case of ∞, i _i / i _o → 1. This is because each strand S ₁
By increasing the distance between to S ₇ enough, the strands of the central S ₇
Means that the current ratios of the outer strands S _{1 to} S ₆ become equal. From this, it is considered that the current distribution can be equalized by forming the untwisted portion at a certain portion of the stranded conductor.

[0027] From the above analysis, to eliminate the degradation in the uniform current distribution by adding series impedance z ₁ to z ₇ for each strand S ₁ to S ₇ or sub-cables superconducting strands S In addition, it is possible to reduce the mutual inductance between each strand or sub-cable by partially increasing the distance between each strand of the stranded wire or the interval between the sub-cables, thereby eliminating degradation. I understand.

FIGS. 4 and 5 show an embodiment of a winding of a power device using a superconducting stranded wire or a superconducting cable according to the present invention. FIG. 4 shows a case where the above-described superconducting cable is used for a transformer. The sub-cable of the superconducting cable 1 is connected to a plurality of secondary windings of the transformer T so as to form a circuit with each secondary winding, and each sub-cable is connected in series to the sub-cable described in the first embodiment. Impedance is added,
The critical current flowing through each sub-cable is made uniform.
That is, as the current flowing through the secondary of the transformer T, a critical current that is a multiple of the number of sub-cables of the critical current flowing through each sub-cable flows.

Next, a case where the secondary winding of the transformer T is one circuit will be described with reference to FIG. In this embodiment, the secondary winding of the transformer T is one circuit, and the superconducting cable 1 used in the above embodiment is connected to the secondary winding.
Also in this embodiment, the critical current between the sub-cables is uniform, and the efficiency of the transformer T itself is very high. In the present embodiment, only the case where the superconducting cable 1 to which the series impedance is added is used as the winding of the transformer has been described. However, the present invention is not limited to this winding. A superconducting cable in which current control means is added to a superconducting cable or each sub-cable may be configured as a winding.

The above embodiment is an example of a preferred embodiment of the present invention, but the present invention is not limited thereto, and various modifications can be made without departing from the gist of the present invention. For example, as shown in FIG. 3, by adding a voltage control means Q ₁ to Q ₇ to uniform critical current flowing to Kakumotosen S ₁ to S ₇ each wire S ₁ to S ₇ of the superconducting stranded wire Can perform the same operation. In the case of this embodiment, the voltage control means Q _{1 to} Q ₇ function as current control means.

A technique for adding series impedances z _{1 to} z ₇ as current control means (FIG. 1),
It is also possible to form a superconducting strands S and parallel for the art (FIG. 2) for setting a predetermined interval between ₁ to S _7.

Further, in this embodiment, the superconducting stranded wire S has been mainly described, but it is needless to say that the present invention can be applied to a superconducting cable. That is, assuming that a superconducting cable is a group of sub-cables of a plurality of superconductors, each sub-cable corresponds to each strand of a superconducting stranded wire, and if impedance Z _{1 to} Z ₇ is added to each sub-cable in series. good. Further, similarly to the stranded wire shown in FIG. 2, a predetermined interval may be provided between the sub-cables.
It may be provided a current control means Q ₁ to Q ₇ for performing voltage control for each strand as well as the sub-cables shown.

[0033]

As is clear from the above description, the superconducting stranded wire or superconducting cable of the present invention is provided with current control means and impedance for each wire or each sub-cable. The current flowing through the sub-cable can be made uniform, and the degradation can be eliminated. That is, the critical current flowing through the superconducting stranded wire and the superconducting cable can be improved.

In the superconducting stranded wire or superconducting cable of the present invention, the twist of each strand or sub-cable is partially widened to increase the distance between them, and the mutual inductance between each strand or sub-cable is reduced. As a result, the current flowing in each element wire or sub-cable can be made uniform to eliminate degradation.

Further, in a power device winding using such a superconducting stranded wire or a superconducting cable, for example, in the case of a transformer, the voltage conversion efficiency is improved.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a first embodiment of a superconducting stranded wire or cable of the present invention.

FIG. 2 is an explanatory view showing a second embodiment of the present invention.

FIG. 3 is an explanatory view showing a third embodiment of the present invention.

FIG. 4 is an explanatory view showing an embodiment of a power device winding using a superconducting stranded wire or cable according to the present invention.

FIG. 5 is an explanatory diagram showing another embodiment of another power device winding.

FIG. 6 is an explanatory diagram illustrating a critical current flowing through each strand of the superconducting stranded wire.

[Description of reference numerals] S ₁ to S ₇ wires z ₁ to z ₇ voltage control means T transformer as an impedance Q ₁ to Q ₇ current control means as a current control means

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-92006 (JP, A) JP-A-59-29306 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01B 12/00-13/00 H01F 5/08

Claims (5)

(57) [Claims] 1. A superconducting stranded wire, comprising: twisting together two or more superconductor strands; and adding a current control means for controlling current for each of the strands. 2. A superconducting cable characterized in that a sub-cable is formed of two or more superconducting stranded wires or superconducting wires, and current control means for controlling current is added to each sub-cable. 3. A superconducting stranded wire characterized in that two or more superconducting wires are twisted together, and the twist of the wires is partially widened to increase the distance between the wires. 4. A superconducting cable characterized in that a sub-cable is formed by two or more superconducting stranded wires or superconducting wires, and the interval between the sub-cables is widened. 5. A power device winding, wherein a power device is wired using the superconducting stranded wire or the superconducting cable according to any one of claims 1 to 4.