JPH08264039A - Superconducting cable - Google Patents

Abstract

PURPOSE: To provide a superconducting cable capable of concurrently securing stability and reducing the AC loss. CONSTITUTION: This superconducting cable is provided with stranded wires twisted with multiple superconducting strands 11...11. The stranded wires are formed with multiple primary stranded wires 12...12 twisted with multiple superconducting strands 11...11, multiple secondary stranded wires 13...13 twisted with multiple primary stranded wires 12...12, and a tertiary stranded wire (high- order stranded wire) 14 twisted with multiple secondary stranded wires 13...13. The electrical resistance value for the unit length between the stranded wires of the same twist order is set larger between the stranded wires having a higher twist order.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting cable for ensuring stability and reducing AC loss of a superconducting device such as a superconducting pulse magnet or an AC magnet.

[0002]

2. Description of the Related Art Conventionally, superconducting cables used for superconducting devices such as superconducting magnets, superconducting transformers, superconducting generators, stator windings and current limiting devices for nuclear fusion devices have been known. Of these, a superconducting cable suitable for a superconducting pulse magnet or an AC magnet is shown in FIG.

A superconducting cable 1 shown in FIG. 17 comprises a primary stranded wire 3 formed by twisting a plurality of superconducting element wires 2 together.
A plurality of the primary twisted wires 3 (bundles) are twisted together to form a secondary twisted wire 4, which is further twisted in the same manner to form a desired high-order twisted wire. It is stored.

However, even with such a high-order twisted wire, depending on the pulse conditions and the like, a coupling current flows due to a change in magnetic flux across the superconducting element wires 2 in the cross-sectional direction of the superconducting cable 1, and this coupling current is applied to the element wires. There was a risk that the heat loss due to Joule heat generated when crossing between the two became large, and that normal conduction was achieved.

Therefore, as a measure for preventing a large heat loss occurring in the superconducting cable 1, the surface of the superconducting element wire 2 is coated with a high resistance material or an electric insulator to increase the electric resistance between the superconducting element wires 2. , The occurrence of AC loss is reduced.

[0006]

However, in the above-mentioned superconducting cable in which the surface of the wire is electrically insulated or has a high resistance, some of the superconducting wire is caused by disturbance such as local heat input. However, if the superconducting transition occurs, the other superconducting element wires cannot maintain the superconducting state, and as a result, the stability of the superconducting cable itself (maintaining a good superconducting state) deteriorates.

That is, as a measure for increasing the resistance between the superconducting wires, the current is redistributed when the currents flowing in the respective superconducting wires are biased or when there is local heat input in the conductor cross section. It was not performed smoothly, and the superconducting state could not be maintained smoothly and stably, which was one of the causes of impairing the stability of the superconducting cable.

[0008] For example, in order to maintain the superconducting state of the superconducting cable when a part of the superconducting element wire is transferred to the normal conducting state due to disturbance such as wire motion, the current is quickly transferred to another adjacent superconducting element wire. This is very important. However, as described above, if the electric resistance between the superconducting wires is increased by the insulation treatment or the like, the current transfer (current redistribution) between the wires is performed only through the path passing through the electrodes at the conductor end. However, it takes time in proportion to the wire length, and it is not possible to expect a rapid current transfer with a particularly long cable. As a result, the superconducting cable may not be highly stable and may be easily quenched (the superconducting state may be lost). As described above, there is a trade-off relationship between reduction of AC loss and securing of stability, and it has been difficult to realize both at the same time.

This is the same reason when the current flowing through each superconducting element wire is biased due to the difference in the length (inductance) of each superconducting element wire and the difference in the connection electric resistance at the current introducing terminal. There is a problem in that the stability deteriorates and the superconducting cable cannot be used as a whole due to the normal conduction transition of one superconducting element wire.

Therefore, in recent years, a superconducting cable aiming at securing such stability and reducing AC loss at the same time has been proposed (for example, Japanese Patent Laid-Open No. 7-14441).

This superconducting cable is applied to a large capacity cable, a pulse cable, etc., and is provided with a plurality of superconducting element wires made of a stabilizing material such as a superconducting filament and copper. Similarly, the primary twisted wires, secondary twisted wires, ..., Higher-order twisted wires are formed by twisting them in sequence. This superconducting cable has a high resistance such as an insulator such as formal or CuNi, Cr or the like on the surface of the superconducting wire in order to reduce the coupling loss (AC loss) due to the coupling current between the wires caused by the fluctuating magnetic field. An electrical short-circuit part that electrically short-circuits each strand for the purpose of securing the stability while performing insulation treatment with the body arranged and quickly shunting the current flowing in the strand that has undergone normal conduction transition to prevent quenching and secure stability. Are formed at predetermined intervals.

However, even in the case of this superconducting cable, no clear standard has been established in selecting the design location such as the location of the electrical short-circuited portion, its pitch, and the resistance value, and the electrical short-circuited portion. Since the specific configuration of the cable was not clear, for example, depending on the cable usage conditions such as when superconducting wires are twisted in multiple stages with a cable length of several hundred meters, and the operation of the twist order, etc. However, it is not clear how to provide the electrically short-circuited portion, how to determine the resistance value of the electrically short-circuited portion, etc., which may make practical application difficult.

The present invention has been made in view of the above-mentioned problems of the prior art, and it is a first object of the present invention to provide a superconducting cable capable of ensuring stability and reducing AC loss at the same time. To do.

A second object of the present invention is to provide a superconducting cable which improves the redistribution and transfer of current to maintain a stable superconducting state and reduces AC loss due to generation of a coupling current. .

Further, while utilizing the advantage of the structure in which the electrical short-circuit portion is provided, the criteria for selecting the optimum location such as the location of the electrical short-circuit portion, its pitch, the resistance value, etc. according to the cable operation are constructed and put into practical use. It is a third object to provide a superconducting cable having a high efficiency. Further, a fourth object is to provide a superconducting cable that is easily constructed by constructing the structure of the electrical short-circuit portion and has improved practicality.

[0016]

In order to achieve the above object, a superconducting cable according to the invention as defined in claim 1 constitutes a primary stranded wire by twisting a plurality of superconducting element wires. In a superconducting cable in which multiple strands are twisted to form a secondary twisted wire, and then the same twisted order is used to form a higher twisted wire, the electrical resistance value per unit length between twisted wires with the same twisting order It is configured such that the higher the order, the greater the value between the twisted wires.

In the invention according to claim 2, when the final twist order of the high order twisted wire is N, at least one twisted wire of any order among the twisted wires having a twist order of (N-1) order or less A high-resistivity film is formed on the outer surface, and also,
As described above, the high-resistivity film may be formed such that the twisted wire having a higher twist order has a larger film thickness than the twisted wire having a lower twist order, and further, as described in claim 4, The coating is formed of a coating material having a higher electrical resistance in a twisted wire having a higher twist order than in a twisted wire having a lower twist order.

In the invention according to claim 5, the twisted wire is set so that the twisting pitch becomes larger as the twisting order becomes higher. Further, as described in claim 6, the primary twisted wire is a superconducting element wire. The twist pitch L
8. Set p1 within the range of Lp1 ≦ 20d, and claim 7.
As described in Section 1, when the diameter of the circumscribed circle of the primary twisted wire is D1, the twisted pitch Lp2 is Lp2 ≦ 30D1.
In the third twisted wire, when the diameter of the circumscribed circle of the second twisted wire is D2, the twist pitch Lp3 is set to Lp3 ≤
The range is set to 40D2.

In the invention according to claim 8, after the high-order twisted wire is constructed, a tensile load equal to or lower than the critical load is applied to the higher-order twisted wire to crimp between the twisted wires. Thus, a high-order twisted wire with a twist pitch of Lpn and a twist order of N is
(N-1) The electrical resistance between the next twisted wires is set to be equal to or more than the square of (Lpn / Lp1) of the electrical resistance between the superconducting element wires of the primary twisted wire of the twist pitch Lp1.

In a tenth aspect of the present invention, a plurality of superconducting element wires are twisted together to form a primary twisted wire, and a plurality of these primary twisted wires are twisted together to form a secondary twisted wire. In a superconducting cable that also composes a high-order twisted wire, the higher-order twisted wire is heated in an inert gas or vacuum to solid-phase diffusion bond the intersection of twists to form an electrical short circuit part. .

The superconducting cable according to the invention of claim 11 is a superconducting element wire at a crossing position of a twisted wire composed of a plurality of superconducting element wires and the twisted wire corresponding to an integer multiple of the twist pitch of the twisted wire. And an electric short-circuit portion having an electric resistance for making the electric resistance value per unit length of the electric resistance value smaller than the electric resistance value at positions sandwiching the intersection position, and the electric short-circuit portion is provided at the intersection position. ing.

Here, the thermal diffusion distance in the longitudinal direction of the superconducting element wire is ld, the thermal conductivity of the superconducting element wire and its heat capacity are κ and ρC, and the time when disturbance is applied to the superconducting element wire is τq. And the thermal diffusion distance ld is

(Equation 5) And the electric resistance value of the electric short-circuited portion is R
c, the electric resistance value per unit length of the superconducting element wire at the time of normal conduction transition is Rn, and the limiting current value and the critical current value determined by the superconducting characteristics of the superconducting element wire and its refrigerant conditions are Ilim and Ic. Then, the electrical resistance value Rc of the electrical short-circuited portion is

## EQU6 ## The range is set to satisfy the conditional expression of 2Rc / (2Rc + Rn × ld) ≦ Ilim / Ic.

A superconducting cable according to a twelfth aspect of the present invention is a unit of the superconducting element wire in which a twisted wire composed of a plurality of superconducting element wires and the superconducting element wires at positions arranged at regular intervals along the longitudinal direction of the twisted wire. An electrical short-circuit portion having an electric resistance for making the electric resistance value per length smaller than the electric resistance value at positions sandwiching the arrangement position, and the electric short-circuit portion is provided at the arrangement position. .

Here, the distance between the electrical short-circuited portions is lc
The thermal diffusion distance in the longitudinal direction of the superconducting element wire is ld, the electric resistance value of the superconducting element wire at the time of normal conduction transition is Rn, the electric resistance value of the electrical short circuit portion is Rc, and the normal conduction value is Let L be the leakage inductance per unit length determined by the mutual impedance characteristics of the superconducting element wire that has transferred and the superconducting element wire that is adjacent to this superconducting element wire and that maintains the superconducting state, and let L be the electrical resistance value of the superconducting element wire. Let τc be the circuit time constant determined by Rn, the electrical resistance value Rc of the electrical short-circuited portion, and the leakage inductance L,
Τh is the time during which transient heat transfer is dominant for the superconducting wire.
When the thermal diffusion distance ld is smaller than the distance lc between the electrical short-circuited portions (ld <lc), the distance lc between the electrical short-circuited portions is

(Equation 7) When the thermal diffusion distance ld is larger than the distance lc between the electrical short-circuited portions (ld> lc), the distance lc between the electrical short-circuited portions is set as follows:

(Equation 8) It is set within the range that satisfies the conditional expression of.

In the invention of claim 13, the twisted wire is
A high-order twisted wire including a primary twisted wire formed by twisting the plurality of superconducting wires and a secondary twisted wire formed by twisting the primary twisted wires with each other. The above-mentioned twist pitches are set under the condition that the least common multiple of each twist pitch in each next twisted wire is equal to the distance between the electrical short-circuited portions.

According to a fourteenth aspect of the present invention, when the least common multiple of each twist pitch of each higher order twisted wire is larger than the distance between the electrical short-circuited parts, the first higher order twisted wire The electrical short circuit portion is provided in the stranded wire from the first order to the arbitrary order when the least common multiple of each twist pitch of the twisted wire up to the arbitrary order is smaller than the distance between the electrical short circuit portions.

A superconducting cable according to a fifteenth aspect of the present invention has a structure provided with a twisted wire composed of a plurality of superconducting element wires, and an induced electromotive force generated in the superconducting element wire due to a change in an external magnetic field. And, based on the twisting pitch of the twisted wire and the generated voltage at the time of normal conduction transition of the superconducting element wire determined by one of the longitudinal thermal diffusion distances of the superconducting element wire, the twisting pitch is The induced electromotive force is set to a range that satisfies the condition that it is smaller than the generated voltage.

In the sixteenth aspect of the present invention, the twisted wire is
A high-order twisted wire including a primary twisted wire formed by twisting the plurality of superconducting wires together and a secondary twisted wire formed by twisting together the primary twisted wires, and each of the high-order twisted wires Based on the total sum of the induced electromotive force for each next twisted wire, the twisting pitch of the next twisted wire, and the generated voltage at the time of normal conduction transition determined by any one of the thermal diffusion distances, Each twist pitch is set in a range that satisfies the condition that the total sum of the induced electromotive forces is smaller than the generated voltage.

According to a seventeenth aspect of the present invention, a superconducting cable is provided with a twisted wire composed of a plurality of superconducting element wires, and the twisted wire is twisted in layers in the circumferential direction having different concentric circle radii at the same pitch. It is a twisted wire of a plurality of layers that are combined, and the electric resistance value per unit length of the superconducting element wire at each crossing position corresponding to the twist pitch of the twisted wire of the plurality of layers is An electric short circuit portion having an electric resistance for making the resistance value smaller than the resistance value is provided at the intersection position.

According to the eighteenth aspect of the present invention, the twisting directions of two adjacent layers of the twisted wires of the plurality of layers are set to be opposite to each other.

In the nineteenth aspect of the invention, the number of layers of the plurality of layers is an even number.

According to a twentieth aspect of the invention, a conduit for accommodating the twisted wire is further provided, and the electrical short-circuit portion reduces the void ratio of the twisted wire orthogonal to the axial direction of the conduit at the intersecting position. Equipped with means.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) A first embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a perspective view showing a typical example of a 3 × 3 × 3 type superconducting cable 10 according to the present invention. The superconducting cable 10 is a superconducting stranded wire conductor used in superconducting devices such as a superconducting magnet of a nuclear fusion device, a superconducting generator, a superconducting transformer, a stator winding, and a current limiter. This superconducting cable 10 is a superconducting stranded wire conductor having a multiple stranded wire structure which is preferably used for a superconducting pulse magnet and an AC magnet. When the superconducting cable 10 is used for a superconducting magnet of a nuclear fusion device, it is housed in a conduit 5 (see FIG. 8) filled with a helium refrigerant or the like, and when used for other superconducting equipment, it is insulated. Covered with spacers.

The superconducting cable 10 is, for example, a superconducting stranded wire conductor having a multi-stranded wire structure with a diameter of about several mmφ, and has a higher order (N
Next: Composed of twisted wires having a twist order of N ≧ 2). The superconducting cable 10 shown in FIG. 1 is a superconducting stranded wire conductor having a third twist order, and is composed of a superconducting element wire 11, a primary stranded wire 12, a secondary stranded wire 13, and a tertiary stranded wire 14. .

As the superconducting element wire 11, a superconducting multi-core wire having a large number of superconducting filaments of the same diameter of, for example, several μmφ, specifically, tens of thousands is used in order to reduce the hysteresis loss. The superconducting element wire 11 has an outer diameter of 1 mmφ or less, for example, about 0.2 mmφ. In the superconducting multi-core wire that constitutes the superconducting element wire, in order to suppress electromagnetic coupling between superconducting filaments to a magnetic field (transverse magnetic field) perpendicular to the multi-core axis and electromagnetic loss (coupling loss between filaments) associated with this coupling, Usually twisted. Each superconducting filament is formed by coating a superconducting material such as NbTi or Nb ₃ Sn with stabilized copper such as CuNi.

If necessary, a sheath portion is provided on the outer periphery of the filament portion of the superconducting multifilamentary wire formed by twisting the superconducting filaments. The sheath portion is made of copper oxide, chromium,
It is formed of a high resistance film such as CuNi or a low resistance film such as silver.

Further, the primary twisted wire 12 of the superconducting cable 10
While a plurality of, for example, three superconducting element wires 11 are twisted together, a plurality of (twisted) primary twisted wires 12 that are twisted together (bundle) are twisted together to form a secondary twisted wire 13. further,
A plurality of (twisted) secondary twisted wires 13 that have been twisted together are bundled to form a tertiary twisted wire 14, and the tertiary twisted wire 14 constitutes the superconducting cable 10 having a third twisted order. The twist pitch of each twisted wire 12, 13, 14 is set to increase as the twist order increases. The superconducting cable 10 is composed of a twisted wire having a twist order of N (N ≧ 2), and in general, the twist order N is often 6 to 8.

On the other hand, in this superconducting cable 10, as shown in FIG. 2, a thin primary coating material 16 is applied (coated) on the outer surface of the primary stranded wire as an electric resistor.
The secondary coating material 17 is also applied as an electric resistor to the outer surface of the secondary stranded wire 13 obtained by twisting a plurality of the primary stranded wires 12 to which the primary coating material 16 has been applied. Further, the tertiary coating material 18 is also applied to the outer surface of the tertiary stranded wire 14 obtained by twisting the secondary stranded wire 13. Each coating material 16,
17, 18 are chromium, copper oxide, CuNi, stainless steel,
It is formed of a high resistance material such as tungsten, nickel, copper sulfide, formal, amorphous alloy, aluminum nitride or the like, or a resistance material such as a semiconductor. Tertiary coating material 1
Reference numeral 8 is a coating for the fourth twisted wire (not shown). The coating thickness of formal is preferably about several μm.

The respective coating materials 16, 17, 18 are coated on the corresponding twisted wires 12, 13, 14 by sputtering, electroplating, baking coating, thermal spraying, dripping or the like. When the coating is performed by sputtering or the like, a coating (coating) having a favorable predetermined film thickness is applied only to the outer surface on the circumscribing circle side of the twisted wires 12, 13, 14 of each twist order, and the coating material wraps around the inside of the twisted wire. Since the coating surface area is small and the coating material can be saved, the coating material is not applied to the contact points between the superconducting element wires 11 forming the primary twisted wire 12, and the superconducting element wires 11 are mutually protected. Can be brought into direct contact with the superconducting wire 11 and the electric resistance between the superconducting wires 11 can be extremely reduced.
Current distribution (redistribution) or current transfer to the adjacent superconducting element wires 11 becomes smooth, and high stability is obtained.
Stability refers to the property of maintaining the superconducting state in a good and stable manner without breaking the superconducting state.

The coating materials 16, 17 and 18 formed on the outer surfaces of the twisted wires 12, 13 and 14 of the respective twist orders have a thicker film thickness as the twist order becomes higher.
The electric resistance value per unit length between the high-order twisted wires is set to be larger than the electric resistance value between the low-order twisted wires. By making the electrical resistance value of the high-order twisted wire larger than that of the low-order twisted wire, the electrical resistance value between the high-order twisted wires can be increased or made into an insulated state. It is possible to eliminate a large path (path) of the eddy current due to the change of the magnetic flux induced in the cross section of the superconducting cable 10 with the change of the external magnetic field caused by the magnetic field, and reduce the AC loss accompanying the generation of the eddy current. be able to. Since the outer surface of the low-order stranded wire, for example, the primary stranded wire 12 is coated, and the superconducting element wires 11 are in direct contact with each other, the electric resistance is extremely small, and even if an eddy current is generated due to a change in magnetic flux, Since the interlinking magnetic flux is small, the AC loss is extremely small.

Next, FIG. 3 shows the relationship between the twisting pitch (twist pitch) of the primary, secondary and tertiary stranded wires 12, 13 and 14 in the superconducting cable 10 and the contact electric resistance between the superconducting element wires (stranded wires). .

It can be seen from FIG. 3 that the shorter the twist pitch, the smaller the contact electric resistance between the strands or between the strands. Specifically, the relationship between (twisting pitch Lp1 of the primary twisted wire 12 / superconducting element wire diameter d) and (electrical resistance between the superconducting element wires 11) is indicated by symbol a. The symbol b indicates the relationship between the (twisting pitch Lp2 / the primary tangential line circumscribing circle diameter D1) of the secondary twisted wire 13 and the (electrical resistance between the primary twisted wires 12), and the symbol c indicates the (twisted pitch of the tertiary twisted wire 14). The relationship between Lp2 / secondary twisted wire circumscribed circle diameter D2) and (electrical resistance between the second twisted wires 13) is shown.

In the primary stranded wire 12, when the twisting pitch Lp1 becomes approximately 20 times or less of the diameter d of the superconducting element wire as shown by the symbol a, the electrical resistance between the element wires sharply decreases, and when it becomes about 15 times or less, the superconducting element It can be seen that the twisted state of the wire 11 is tight. That is, in the primary twisted wire 12, the twist becomes loose when the twist pitch Lp1 exceeds about 20 times the superconducting element wire diameter d, and when the twist pitch Lp1 is less than 15 times, the twist becomes tight. FIG.
Therefore, in the case of the primary twisted wire 12, the twist pitch Lp1 is approximately 20 times or less of the superconducting element wire diameter d, preferably 15 ≦ Lp1 /
It is desirable that d ≦ 20.

Further, referring to FIG. 3, in the case of the secondary twisted wire 13, when the twisting pitch Lp2 becomes about 30 times or less of the circumscribed circle diameter D1 of the primary twisted wire, the electrical resistance between the primary twisted wires 12 is reduced. It decreases sharply, and when it becomes 25 times or less, the secondary twisted wire 13
It can be seen that the twisted state of the primary twisted wire 12 constituting the above is tight. Therefore, in the case of the secondary twisted wire 13, it is desirable that the twisting pitch Lp2 is approximately 30 times or less of the circumscribed circle diameter D1 of the primary twisted wire 12, and preferably in the range of 25≤Lp2 / D1≤30. Similarly, in the case of the tertiary twisted wire 14, the twist pitch Lp3 is about 40 of the circumscribed circle diameter D2 of the secondary twisted wire 13.
It is desirable that it is not more than twice, preferably in the range of 35≤Lp3 / D2≤40.

Generally, the superconducting cable 10 from FIG.
If the twisting pitch of the twisted wire becomes smaller as the twisting degree becomes smaller, the contact electric resistance between the superconducting element wires or between the twisted wires of the corresponding twisting degree becomes smaller, and the adjacent superconducting element wires 11 or the low-voltage side twisted wires are twisted. Current can be smoothly distributed to or transferred to the wires, and the superconducting state can be maintained, that is, stability can be ensured.

Specifically, each twisted wire 1 of the superconducting cable 10
Out of 2, 13, and 14, the superconducting element wires 11 forming the primary twisted wire 12 are in direct contact with each other via a contact point, have a strong electric coupling force, and have a small electric resistance between the superconducting element wires 11. Therefore, if for some reason, for example, one of the superconducting element wires 11 forming the superconducting cable 10 undergoes normal conduction due to local heat input to the superconducting cable 10, the superconducting element wire 11 adjacent to the superconducting element wire 11 that has undergone the normal conduction transition will be Multiple superconducting wires 1
A large amount of current can be rapidly transferred to 1 to reduce the Joule heat generation of the superconducting element wire 11 that has undergone the normal conduction transition, and the element wire 11 can be restored to the superconducting state again. That is, in the primary stranded wire 12 having a small twist order, the electric coupling force between the superconducting element wires 11 is strong, the mutual inductance is large, and a rapid current transfer occurs between adjacent superconducting element wires maintaining the superconducting state. The current and the current redistribution property, it is possible to quickly guide the current flowing through the superconducting element wire 11 in the normal conducting state to the adjacent superconducting element wire and maintain the superconducting state again, so that the stability is improved. You can

Therefore, in the primary stranded wire 12 for which a smaller electric resistance between strands is desired, the twist pitch Lp1 is set to 20 times or less of the diameter d of the superconducting element, that is, Lp1 / d≤20. Ensure good electrical contact between 11
High stability can be maintained. Superconducting cable 1
0 is generally a 6th or 7th twisted wire with a high twist order. When this higher twisted wire is used, the secondary and tertiary twisted wires 13 and 14 do not contribute to the increase in AC loss. , It becomes a low-order stranded wire. As with the primary twisted wire 12, it is preferable that the secondary twisted wire 13 and the lower twisted wires up to about the tertiary twisted wire 14 keep the electrical resistance between the twisted wires low. To this end, in the case of the secondary twisted wire 13, the twist pitch Lp2 is 30 times or less of the circumscribed circle diameter D1 of the primary twisted wire 12, and the tertiary twisted wire 14 is used.
In case of, the twist pitch Lp3 is set to the circumscribed circle diameter D of the secondary twisted wire 13.
By setting it to 40 times or less of 2, stability can be improved and a superconducting cable with less AC loss can be obtained.

On the other hand, in order to further reduce the AC loss in the twisted wire having a small twist order, that is, in the low order twisted wire, the superconducting element wire is electrically insulated or has a high resistance as in the conventional superconducting cable shown in FIG. By coating the wire and providing an electrical short circuit (contact) at every integer multiple of the twist pitch, an electric circuit that causes current redistribution can be formed into a small one (small loop), and quick current redistribution and current Transferability can be secured. By providing an electrical short-circuit portion for each integral multiple of the twist pitch, it is possible to completely eliminate the coupling loss between the superconducting wires. For example, primary to tertiary stranded wire 1
By providing an electrical short-circuit portion having an integral multiple of the twist pitch at any of the steps 2, 13, and 14, it is possible to quickly reallocate the current without increasing the AC loss. In this case, the superconducting wire may be covered with a coating material of an electric insulator or a high resistance material.

In one embodiment of the present invention, the superconducting cable 1
Coating material 16, 17, 1 applied to each stranded wire of 0
8 shows an example in which the same type of high resistance material is used and the wall thickness (layer thickness) of the coating material is changed to increase the electrical resistance between the higher-order twisted wires to increase the insulation effect. ,
As shown in FIG. 4, a high resistance material or an insulating material having different electric resistance may be used as the coating material.

In the superconducting cable 10A shown in FIG. 4, the electrical resistance is higher than that of the primary coating material 20 as the twisting order of the twisted wire is higher, or coating is performed using coating materials 21 and 22 of a hard high resistance material. Good. When using a coating material of a high resistance material or an insulation material having a different electric resistance, each coating material 2
It is not always necessary to change the film thickness (layer thickness) of 0, 21, 22.

Further, the superconducting cable 10 is constructed by twisting high-order twisted wires together, and then a tensile load below the critical load is applied to the high-order twisted wires to crimp (adhere) the twisted wires of the high-order twisted wires. ) May be done. By applying pretension to the high-order twisted wires of the superconducting cable 10, it is possible to obtain a superconducting cable in which flexibility is eliminated and the electrical resistance between the twisted wires is reduced even if the twist pitch is increased in the low-order twisted wires. .

Further, in the superconducting cable 10, considering that the AC loss caused by the eddy current generated between arbitrary superconducting element wires in the cable section (conductor section) is proportional to the square of the twist pitch ratio, A superconducting cable having a twist order of Nth order may be configured as follows.

That is, the superconducting cable 10 is a high-order twisted wire having a twist pitch of Lpn and a twist order of N (N-
1) By setting the electrical resistance between the following twisted wires to be equal to or more than the square of the electrical resistance (Lpn / Lp1) of the superconducting wire of the primary twisted wire of the twist pitch Lp1, The generated eddy current loss can be equalized, and the AC loss can be reduced.

FIG. 5 shows a superconducting cable 10 according to the present invention.
It shows another modified example of B.

Superconducting cable 10 shown in this modification
B is a case where the coating material is not applied to the outer surface of the primary twisted wire 12, but the primary coating material 23 of the high resistance is applied as an electric resistance to the outer surface of the secondary twisted wire 13 in which the primary twisted wires 12 are twisted. It was made.

In this superconducting cable 10B, since the outer surface of the primary twisted wire 12 is not coated with a coating material, not only can the direct contact between the superconducting element wires 11 be effectively achieved, but also a high resistance material is coated. It is possible to make direct contact between the untwisted primary stranded wires 13 and to reduce the electric resistance value between the superconducting element wires 11 and between the primary stranded wires 12, thus facilitating the distribution of the current and the secondary twisted wire. Line 1
It is possible to increase the electric resistance value between the three wires, increase the electric resistance between the higher-order twisted wires, and reduce the AC loss.

The superconducting cable 10B may be formed by coating a high-order stranded wire of the final twist order N with a coating material of a high resistance material or an insulating material, but the superconducting cable 10B is housed in the conduit 5 shown in FIG. Therefore, it is not necessary to apply a coating material.

In this superconducting cable 10B, when the final twist order of the twisted wire is N, at least one twisted wire of an arbitrary order among the twisted wires having a twist order of (N-1) order or less is on the surface. It may be covered with a coating material 23 of a high resistance material.

In this case, no coating is applied to the superconducting element wires 11 or the lower-order twisted wires in the twisted wires of the required order on which the high-resistive film (coating material 23) is applied, Since it is in direct contact with the wire, the electrical resistance between the wires and between the low-order twisted wires is extremely small, and the current redistribution and transferability can be sufficiently secured.

Furthermore, in a twisted wire of a higher order than a twisted wire coated with a high-resistance film, the electrical resistance between the higher-order twisted wires is greater than the existence of the film, so that the electrical resistance and insulation between the twisted wires are improved. It is possible to increase and effectively reduce the AC loss due to the eddy current loss.

Further, in the superconducting cable, the coating material is not applied to the low-order twisted wire having a twisting order lower than the primary twisted wire 12 by several stages, and the coating material is applied from the twisted wire at the next stage in which the low-order twisted wires are twisted together. May be applied.

The superconducting cable is composed of the superconducting wires 11
A low resistance material, for example, silver plating is applied to the outer surface of the superconducting element wire 11 and the superconducting element wires 11 applied with the low resistance element are twisted together to form a primary stranded wire 12. The primary coating material is applied (coated) to form a high resistance coating, and the twisted wire 14 on the higher order side of the secondary twisted wire 13 is formed.
Alternatively, a coating material may be sequentially applied as shown in FIGS.

Instead of silver-plating the superconducting element wires 11, a sheath portion or a superconducting filament (NbTi material or Nb ₃ Sn material of the superconducting material is CuNi Stabilized copper (such as that coated with stabilized copper) is removed by acid washing or the like to activate it, and a plurality of activated superconducting element wires 11 are twisted together to form a primary twisted wire. A plurality of the primary twisted wires 12 are twisted together to form a secondary twisted wire 13, and further,
A plurality of secondary twisted wires 13 are twisted together to form a tertiary twisted wire 14, and after twisting the third twisted wires 14, the outer surface is coated with a coating material of a high resistance material, followed by an inert gas atmosphere or vacuum. Heat treatment is performed at a temperature of several hundreds of degrees Celsius to 1000 degrees Celsius, and fusion is performed by solid-phase diffusion bonding at the places where the strands 11 of the lower-order twisted wires that are not coated with the high-resistance coating material are in contact with each other. Alternatively, the electrical short circuit portion may be formed.

By constructing the superconducting cable in this way and performing solid-phase diffusion bonding at the twisting intersections of the superconducting element wires in the low-order side twisted wires, the electrical conductivity between the superconducting element wires of the twisted wires with a low twist order is obtained. The resistance can be remarkably lowered, and the coating material is interposed between the twisted wires having a large twist order, so that the electric resistance can be increased.

Although the first embodiment of the present invention shows an example in which the superconducting cable is a superconducting stranded wire conductor having a 3 × 3 × 3 triple stranded wire structure, the present invention is not limited to this. Not a thing. For example, as shown in FIG.
The superconducting stranded wire conductor of the 6 × 6 × 6 type multi-stranded wire structure shown in FIG.

That is, in this superconducting cable 10C, six superconducting element wires 11 are twisted together to form a primary twisted wire 25,
Subsequently, six primary twisted wires 25 are twisted together to form a secondary twisted wire 26, and six secondary twisted wires 26 are twisted together to form a tertiary twisted wire 27.
Is configured. Further, the third twisted wires 27 may be sequentially twisted in the same manner thereafter to form a multi-twisted wire structure of fourth order or more. In this case, the non-superconducting wires 28, 29, 30 are arranged as reinforcing core wires at the center of each level of the multi-stranded wire. By using the superconducting wires instead of the non-superconducting wires,
The 6 × 6 × 6 type multi-stranded wire conductor may be a 7 × 7 × 7 type multi-stranded wire conductor.

Further, the superconducting cable 10D may have a rectangular stranded wire conductor as shown in FIG. 7 or may have a stranded wire conductor structure of another shape.

A rectangular superconducting cable 10D shown in FIG.
Is composed of six (or seven) superconducting wires 11 to form a primary stranded wire 25, and a large number of the primary stranded wires 25 are provided around a non-superconducting wire 32 as a reinforcing core material having a rectangular cross section. Although the secondary stranded wire 33 is formed by winding the stranded wire, a stranded wire having a twist order of three or more may be wound around the non-superconducting wire 32.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS. This second embodiment is applied to a superconducting cable in which electrical short circuits are provided at every integer multiple of the twist pitch, and conditions for selecting optimum values such as the resistance value of the electrical short circuits and their distance (arrangement interval). Is specifically specified.

First, an example of setting the resistance value of the electrical short circuit portion will be described with reference to FIG.

FIG. 8 is a graph for explaining an example of setting the resistance value in a superconducting cable in which an electrical short circuit portion is provided for each twist pitch. The horizontal axis shows the short circuit resistance value Rc (Ω) and the normal conduction resistance value Rn × ld. Resistance ratio (2Rc / (2Rc
+ Rn × ld)) is set, and the vertical axis is set to the current ratio (I / Ic) between the current value I and the critical current value Ic flowing during the normal conduction transition, and the limiting current value Ilim is added to the relationship between them. The short-circuit resistance value Rc is obtained.

The "normal conducting resistance value Rn × ld" is the resistance value Rn (Ω / m) per unit length generated when the superconducting element wire completely transitions to the normal conducting state and the heat in the longitudinal direction of the superconducting element wire. It is a resistance value represented by the product of the diffusion distance ld (m).
"Thermal diffusion distance ld" means that the heat generated in the superconducting element wire adiabatically diffuses into the refrigerant during a short time (for example, about 1 ms) to which disturbance such as wire motion is applied. It means the length of the normal conducting region (temperature rising region) generated in the longitudinal direction of the strand.

Specifically, the length of the temperature rising region in the longitudinal direction of the wire with respect to the time (τq) in which a locally generated disturbance such as local heating is applied to the superconducting wire, that is, the thermal diffusion distance ld.
Is the thermal conductivity in the longitudinal direction of the superconducting wire and its heat capacity are κ and ρC,

[Equation 9] It is expressed by the formula. Regarding κ and ρC in the formula [9], the thermal conductivity and heat capacity of the constituent material of the superconducting element wire are adopted when the insulating film on the surface of the superconducting element wire has good thermal insulation. However, if there is no insulator on the surface of the superconducting wire and there is almost no heat shield, for κ, the thermal conductivity of the constituent material (stabilizer) of the superconducting wire, for example, stabilized copper. It is preferable to use the heat capacity of the refrigerant distributed to one superconducting element wire for ρC (for example, in the case of supercritical helium, the heat capacity distributed to about 30 μm around the element wire).

For example, taking a cable-in-conduit type forced cooling conductor as an example, the time period during which disturbance (local heating) such as wire motion is applied is about 1 ms, and the thermal diffusion of the wire heating portion against the local heating is caused. In the case of a superconducting element wire having a wire diameter of 1 mm and a copper ratio (ratio of copper (stabilized copper) to the total cross-sectional area of the superconducting filament) of 2, the distance ld is about 100 mm when calculated from the above [Formula 9]. Become. In this superconducting element wire, the resistance value Rn generated during the normal transition
Is about 0.5 mΩ / m per unit length, so l
When d = 0.1 m and Rn = 0.5 mΩ / m, the normal conducting resistance value Rn × ld generated by the disturbance is 50 μΩ.

The "limit current value Ilim" is the amount of Joule heat generated (Rn × I ² ) per unit length when the superconducting wire changes to the normal conducting state, and the refrigerant arranged around the superconducting wire is constantly. Amount of heat that can be taken away (h x A x (Tc-T
b)) means a current value (a limiting current value based on Stekly's condition) when they are equal to each other. Here, in the equation for calculating the heat quantity, h is the steady state heat transfer coefficient of the refrigerant, A is the surface area per unit length of contact between the refrigerant and the superconducting element wire, Tc is the critical temperature of the superconducting element wire, and Tb is the temperature of the refrigerant. .

Therefore, as a condition for stabilizing the superconducting element wire that has changed to the normal conducting state again to the superconducting state, it is necessary that the current value I flowing through the superconducting element wire that has changed to the normal conducting state is constantly smaller than the limiting current value Ilim. Becomes

Therefore, the resistance ratio Rx determined by the current ratio Ry (Ilim / Ic) when the current value I becomes the limiting current value Ilim and the normal conducting resistance value Rn × ld and the short circuit resistance value Rc.
Focusing on the relationship with (2Rc / (2Rc + Rn × ld)), the condition that the resistance ratio Rx is equal to or less than the current ratio Ry, that is,

## EQU10 ## The short-circuit resistance value Rc is set in a range that satisfies the conditional expression of 2Rc / (2Rc + Rn × ld) ≦ Ilim / Ic.

When the short circuit resistance value Rc is set in this way,
Most of the current flowing in the superconducting wire that has undergone a superconducting transition is easily shunted to the adjacent superconducting wire that maintains the normal conducting state, and Joule heat generation due to the normal conducting resistance is suppressed, so the superconducting cable is stable against external disturbances. It is possible to significantly improve the sex.

The limiting current value Ilim and the critical current value I
The current ratio Ry (Ilim / Ic) determined by c is about 1/2 in the case of a large-capacity conductor, so Ilim / Ic =
Substituting this into the formula [Equation 10] by halving

[Equation 11] The conditional expression of is obtained. Therefore, Ilim / Ic = 1/2
In the case of, the normal conduction resistance value Rn × ld is the short circuit resistance value Rc.
By setting the short-circuit resistance value Rc in a range that is twice or more of the above, the same effect as described above can be exhibited. In order to obtain a sufficient transition current under the condition of [Equation 11], 2Rc is about ⅕ or less of Rn × ld, that is, the short-circuit resistance value Rc is the normal conducting resistance value (Rn × ld) of the wire. About 1/1
It is desirable to set it to 0 or less.

Next, an example of setting the distance between the electrically short-circuited portions will be described with reference to FIGS. 9 and 10.

FIG. 9 is a schematic diagram for explaining a transition current from the superconducting element wires by using an electric circuit (equivalent circuit) between the superconducting element wires. In the circuit configuration shown in the figure, an electrical short-circuit portion 32, 32 is provided between a wire 30 that has undergone normal conduction transition due to disturbance and a wire 31 that is adjacent to the wire 30 and that maintains a superconducting state. Are connected at a predetermined interval, that is, a distance lc.

Here, when the normal conduction transition of the wire 30 occurs, 2
A transition current i3 that flows in a loop between the two short-circuit portions 32 and 32 via the two wires 30 and 31 is generated. This transition current i3 flows in the direction opposite to the current il on the side of the strand 30 that has undergone the normal conduction transition, and flows in the same direction as the current i2 on the side of the strand 31 that maintains the superconducting state. In other words, the current il flowing through the wire 31 that has undergone the normal conduction transition is the same as the wire 3 connected in parallel.
1 normal conducting resistance (Rn × Ld) and 2 short-circuit parts 32, 3
It is equivalent to a circuit that divides the current according to the resistance ratio with the combined electric resistance (2Rc) of 2.

It should be noted that, in the circuit shown in FIG. 9, the above-mentioned stability condition is that the electric current il flowing through the wire 31 that has undergone the normal conduction transition is the combined electrical resistance of the short-circuited portions 32, 32 rather than the normal conduction resistance (Rn × Ld) side. It defines the conditions for splitting a large amount of flow to the (2Rc) side.

FIG. 10 shows a circuit time constant τc based on the above circuit configuration when the distance lc between the short-circuited portions is changed.
In the graph for comparing the relationship between (sec) and the thermal diffusion time constant τh (sec) to the refrigerant, the horizontal axis is the distance lc between the short-circuited portions, and the vertical axis is the circuit time constant τc. The condition that the circuit time constant τc is smaller than the thermal diffusion time constant τh (τ
The distance lc between the short-circuited portions is calculated so as to satisfy c <τh).

"Circuit time constant τc" is usually the resistance value Rn at normal conduction per unit length of the superconducting element wire, and the leakage inductance L (H / m) per unit length of the superconducting element wire.
And the electric resistance value Rc of the short circuit portion. The “heat transfer time constant τh” is the time during which the transfer capacity of the refrigerant can be maintained at a larger value than that in the steady state. The “leakage inductance L” is the self-inductance L1 of the strand 30 that has changed to the normal conducting state, the self-inductance L2 of the strand 31 that maintains the superconducting state, and the mutual inductance of the both 30, 31 in the circuit shown in FIG. M and (i.e., L = L1 + L2-2M).

As shown in FIG. 10, the distance lc between the short-circuited portions
Is smaller than the thermal diffusion distance ld in the longitudinal direction of the superconducting element wire (ld> lc), the circuit time constant τc maintains a substantially constant value regardless of the change of the thermal diffusion distance ld, and the distance between the short-circuited portions. In the range where lc is larger than the thermal diffusion distance ld (ld <lc), the circuit time constant τc increases in proportion to the distance lc.

Therefore, when the distance lc between the short-circuited portions is obtained, the resistance value Rn per unit length, the distance lc between the short-circuited portions, and the normal-conduction resistance value of the superconducting element wire that determines the circuit time constant τc The time when the refrigerant controls transient heat transfer by adopting the value (Rn · ld when ld <lc, Rn · lc when ld> lc) obtained by the smaller product of the thermal diffusion distances ld. In the inside, that is, in the time when the cooling capacity of the refrigerant is large, the current is quickly transferred. Expressing this with an equation, when ld <lc,

(Equation 12) Is expressed by the conditional expression of, and when ld> lc,

(Equation 13) It is represented by the conditional expression. Therefore, in this embodiment, the distance lc between the short-circuited portions is set in a range that satisfies the stability condition expressed by the formula [12] or the formula [13].

Taking, for example, a superconducting cable applied to a nuclear fusion device using supercritical helium at a temperature of 5K or less as a refrigerant, the transient heat transfer capacity of supercritical helium is higher than that in the steady state. The heat transfer time constant τh is about 10 ms.

In this superconducting cable, the inductance L between the superconducting element wires is 5e-7 (H / m). The inductance L is, for example, a superconducting element wire such as a cable-in-conduit type forced cooling conductor, that is, a wire diameter of 0.6 to 1.
In the case of about 0 mm (of which the outer diameter of the region where the superconducting filament exists is about 0.4 to 0.8 mm), the center distance between the strands (or twisted wires) is defined as d, and the effective region of the superconducting filament is effective. When the radius is a,

[Equation 14] It is obtained by the equation of, and becomes about 0.5 μH / m or less.

Further, in this superconducting cable, the normal conducting resistance value Rn · ld is usually about 50 μΩ. Therefore, when it is assumed that the short circuit resistance value Rc is sufficiently smaller than the normal conduction resistance value Rn · ld, the distance lc between the short circuit portions is τc = (L·lc) / (Rn · ld) ≦ 1
It is a range satisfying the condition of 0 ms, that is, about 1 m or less. By setting the distance lc in this range, the current transfer can be obtained within a time period sufficiently early with respect to the decay time of the heat transfer capacity.

When the refrigerant is liquid helium at atmospheric pressure, the heat transfer time constant τh is about 100 ms. Therefore, when the distance lc between the short-circuited portions is calculated in the same manner as described above, it becomes about 10 m or less, which is supercritical. It is about 10 times that of helium.

As described above, since the resistance value of the electrical short-circuited portion and the distance between the electrical short-circuited portions are set, another superconducting element which maintains the superconducting state even when a part of the wire is changed to the normal conduction state. The current can be easily transferred to the wires, which allows high stability to be obtained, and the inter-wire coupling loss due to the magnetic field fluctuation can be canceled in the circuit formed between the electrical short circuits. Therefore, a conductor with low AC loss can be realized at the same time.

Next, a case where the stability condition based on the resistance value of the electrical short-circuited portion and the distance between the electrical short-circuited portions obtained above is applied to the high-order twisted wire will be described.

First, in the above-described superconducting cable having a high-order twisted wire structure, the twisting pitch may be different for each twisted wire of each order. In this case, the distance lc between the electrical short-circuited parts obtained above is the distance Lmi which is the least common multiple of the twist pitch of each order.
By setting the twist pitch of each order to be n,
The above-mentioned stability condition can be satisfied in all orders of twisted wires.

Further, in a superconducting cable such as a large-capacity multi-strand wire, it may be difficult to apply the above-mentioned stability condition to a final twist order twisted wire having a long twist pitch. In this case, an electrical short-circuit portion is provided not by all twisted wires of all orders but by twisted wires of the twist order satisfying the condition of Lmin <lc.

That is, when the least common multiple Lmin in all the twisted wires becomes larger than the distance lc between the electrical short-circuit parts obtained above, the least common multiple from the first order to an arbitrary order is obtained, and the least common multiple is the above. An electrical short-circuit portion is provided on each twisted wire having an arbitrary order or less when the distance is smaller than the distance lc between the electrical short-circuit portions obtained in step 1. A means for electrically short-circuiting is provided for each twisted wire having an order larger than an arbitrary order. As a result, it is possible to secure stability up to a twisted wire having a low order among the orders, that is, a twisted wire having a small twist pitch. In general,
The current transfer between the strands most effectively acts on the strand closest to the normal-conducting transition strand, and the higher the order, the smaller the shunting effect.Therefore, in superconducting strands with a high twist order, It is not necessary for all orders of stranded wire to meet the above stability conditions. In this case, the stability of the superconducting cable can be sufficiently ensured only by providing an electrical short-circuit portion on the part of the twisted wires of the order.

Next, first to fifth application examples of the second embodiment will be described with reference to FIGS. 11 to 15. In addition to the advantages of high stability and low AC loss, each of the application examples is applied to a superconducting cable in which an electrical short circuit portion is specifically formed and a high current density is also taken into consideration.

The superconducting cable of the first application example shown in FIG. 11 has a plurality of superconducting element wires 40 ... 40 whose surfaces have been subjected to insulation treatment (or resistance increasing treatment) and has concentric circles around the axial direction. In the direction along the longitudinal direction at the same twist pitch lp, and an electrical short circuit portion (or a portion having a smaller electric resistance than other portions) 41 for each integer multiple of the twist pitch lp.
41 is provided. Since the strands 40 ... 40 are arranged concentrically in this manner, the void ratio (porosity) of the superconducting cable can be reduced to about 20%, and the void ratio of the conventional superconducting cable with many twist orders (usually, About 36 ~
38%), the current density could be significantly increased.

Next, a cable-in-conduit type forced cooling conductor will be taken as an example. In this case, the electrical short circuit can be formed for each integral multiple of the pitch by increasing the contact pressure between the strands so that the cross-sectional area is periodically small for each twist pitch, that is, the void ratio is small. . An example of this superconducting cable is shown in FIGS.

In the superconducting cable of the second application example shown in FIGS. 12A and 12B, a plurality of superconducting element wires 51 ... 51 twisted in a cylindrical conduit 50 and each superconducting element wire 51. … Cylindrical cooling channel 5 in the center of 51
2 are arranged, and 2 is arranged on the surface of each strand 51 ... 51.
A high resistance material such as chromium, stainless steel, and titanium having a thickness of 10 μm is coated by a method such as plating and sputtering. In this superconducting cable, the cooling channel 5
53 are provided integrally or separately on the outer peripheral surface side of the cooling channel 52 at each lp of the twist pitch of the element wires 51 ... 51 with a plurality of annular convex portions (outer diameter enlarged portions) 53 ... 53 having an outer diameter larger than 2. As a result, the contact pressure between the individual wires 51 ... 51 is increased to lp for each twist pitch. Therefore, in this superconducting cable, it is possible to easily form the electrical short-circuit portion for each twist pitch where the contact pressure is increased.

In the superconducting cable of the third application example shown in FIG. 13, a plurality of twisted superconducting element wires 61 ... 61 are arranged in a cylindrical conduit 60, and a plurality of inner diameters smaller than that of the conduit 60 are arranged. The annular convex portion (inner diameter reduced portion) 62 ... 62 is formed by twisting the strands 61 ..
The contact pressure between the element wires 61 ... 61 is increased for each twist pitch lp by integrally or separately providing the conduit 60 on the inner peripheral surface side.

In the superconducting cable of the fourth application example shown in FIG. 14, a plurality of superconducting element wires 71 ... 71 having multi-layered twists are arranged in a cylindrical conduit 70. A metal tape (or insulating tape) of copper, stainless steel or the like having a tape width that is sufficiently smaller than the size of the conductor at every integer multiple of the twist pitch in at least one of the inner circumference of the inner layer and the outer circumference of each layer By winding 72, the contact resistance between the individual wires 71 ... 71 is reduced for each integer multiple of the twist pitch lp.

In the case of a superconducting cable in which a superconducting element wire is formed of a heat-treated conductor such as Nb ₃ Sn, the above effect can be further enhanced by diffusion-bonding pressure points during heat treatment of the conductor. Further, even in the case of a non-heat-treated conductor such as NbTi, heat treatment under a temperature condition of 100 to 400 [deg.] C. enables solid-state joining of the pressure points, and the above effect can be enhanced.

In the superconducting cable of the fifth application example shown in FIG. 15, superconducting element wires 81 ... 81 are layered in the conduit 80 in the circumferential direction of different radii of concentric circles (one layer 82, 2 in the figure).
(See layer 83) and all are twisted and arranged at the same twist pitch lp. Here, a cylindrical cooling channel 84 is provided in the center of each element wire 81 ... 81, and the first layer 82 and the second layer 8 are formed.
The electrical short-circuit portions 85 ... 85 are provided for every integer multiple of the twist pitch lp of each of the element wires 81 ... 81 of No. 3. In this way, each wire 81
Since 81 are arranged in layers with different radii of concentric circles, the void ratio can be reduced to about 20%.

In this superconducting cable, each adjacent layer 8
Since the twisting directions of Nos. 2 and 83 are opposite to each other, the effect of increasing the cooling area and the effect of the longitudinal magnetic field due to the twisted wires can be offset from each other. In addition, the number of layers of concentric circles is even (Fig. 1
5 has two layers), the influence of the coupling current (drift) due to the longitudinal magnetic field in the conductor longitudinal direction can be almost completely canceled out, and the effect of high stability can be maximized.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIG. This third embodiment is applied to a conventional type superconducting cable that does not include the electrical short-circuiting part described in each of the above-described embodiments, and selects the optimum values such as the twist pitch and the conductor diameter of the twisted wire in the superconducting wire. The conditions are specifically specified.

First, an example of setting the twist pitch and the conductor diameter of the twisted wire will be described with reference to FIG.

FIG. 15 is a graph for explaining the relationship between the induced electromotive force and the normal conductive pressure with respect to the rate of change of the magnetic field. The horizontal axis is the product of the twist pitch lp of the twisted wire in the superconducting wire and the conductor diameter D (lp × D). ) Is taken and the vertical axis is the induced electromotive force e generated between the wires due to the change of the external magnetic field, and the induced electromotive force e and the electromotive force (Rn
Xld), the optimum value of lp × D is obtained. Here, "induced electromotive force e" is e = -dφ / d
It means the electromotive force obtained by the equation of t = -d (B · lp · D / π) / dt.

Here, as a condition for preventing the coupling current between the wires from disturbing the current redistribution between the wires, the magnetic field change rate (dB
/ Dt) (in the example in the figure, B1 ... B3 (dots omitted)), the induced electromotive force e is smaller than the normal conduction pressure Rn × ld, and the arbitrary magnetic field change rate experienced by the conductor is observed. Lp for the condition of e ≦ Rn × ld
Determine the xD range. Lp × D determined in this way
The twist pitch lp of the stranded wire and the conductor diameter D are set from the range.

For example, in the wire (conductor) normally used for a superconducting cable, the voltage in the normal conducting region caused by the locally generated disturbance is 50 μΩ × 100 A = 5 m.
V, and assuming that the magnetic field change rate is 0.3 T / s,
The range of lp × D in which the induced electromotive force e based on the magnetic field change satisfies the condition (e ≦ 5 mV) equal to or lower than the normal conduction generation voltage is 0.
・ It becomes less than 05m ² .

In the case of a superconducting cable having a plurality of twisted wires, the sum of the induced electromotive force e is obtained for each twist order, and the sum of the induced electromotive force e is within the above-mentioned thermal diffusion distance ld and twist pitch lp. The range of lp × D may be determined under the condition that it is smaller than the normal conduction generation voltage Rn × ld which is determined by the smaller distance.

By thus determining the range of lp × D and setting the twisting pitch lp and the conductor diameter D, even when the strands are connected in multiple stages, a sufficiently large transition current can be obtained in the presence of the coupling current. And a stable superconducting cable can be provided.

[0114]

As described above, in the superconducting cable according to the invention described in claim 1, the electric resistance value per unit length between twisted wires having the same twist order is calculated as Since it has been increased, the electric resistance value per unit length between the twisted wires of the same twist order is set to be equal to or more than the electric resistance value between the twisted wires one step before, and the electric resistance value between the higher-order twisted wires is increased. ,
The electrical resistance between the low-order stranded wires can be made small, and the eddy current path induced in the cross section (conductor cross section) of the superconducting cable due to changes in the external magnetic field (generation of alternating magnetic field due to alternating current) is of high order. It is hard to occur between the side twisted wires due to the large electrical resistance,
A path with a large coupling current can be eliminated, and the coupling loss (AC loss) between the strands can be reduced. Further, since the magnetic fluxes that interlink between the lower-order twisted wires are small, the AC loss due to the coupling current is very small and can be almost ignored.

Also, even if local heat input or current bias occurs in this superconducting cable and one superconducting element wire changes to the normal conducting state, the electrical resistance between the lower-order twisted wires is small, and On the side, the superconducting wires in the stranded wire have strong electrical coupling (coupling) between adjacent superconducting wires, and for the superconducting wires that maintain the superconducting state, the electrical resistance between the wires is small, so Since the current quickly moves to the neighboring superconducting element wires and the current redistribution and current transferability are good, it is possible to reduce and suppress the Joule heat generation of the superconducting element wires that have undergone the normal conduction transition. Since it is possible to restore the superconducting element wire that has changed to the normal conducting state to the superconducting state again, it is possible to maintain the superconducting state at all times without destroying the superconducting state as a whole, and improve the stability.

In the invention according to claim 2, among the high-order twisted wires having the final twist order of the Nth order, at least one of the twisted wires of the (N-1) th order and below is formed on the outer surface of the twisted wire, Since the high resistance coating is formed, the superconducting element wire between the twisted wires of the required order on which the high resistance coating is applied does not have a coating on the part that contacts each other, so the electrical resistance between the twisted wires changes. No, it's small.

When the twisted wires coated with the high-resistivity film are further twisted to form a higher-order twisted wire, the electrical resistance between the higher-order twisted wires is large, which causes a coupling loss. AC loss is small. Therefore, this superconducting cable can improve the redistribution property of the current transfer between the superconducting wires, improve the stability, and reduce the AC loss.

According to the third aspect of the present invention, since the film thickness of the high resistance material coated on the outer surface of the twisted wire having a high twist order is increased, the electrical resistance between the twisted wires increases as the twist order of the twisted wire increases. The value can be increased, and in the superconducting cable according to claim 4, a material having a high resistivity can be coated on the outer surface of the twisted wire as the twist order increases, and both of them can be made different depending on the twist order. As a result, it is possible to provide a difference in the electric resistance value between the twisted wires, and it is possible to further increase the stability and reduce the AC loss obtained according to the second aspect.

According to the fifth aspect of the present invention, the twist pitch of the twisted wire is increased as the twist order is increased. Therefore, a twisted wire having a higher twist order can have a larger twist pitch. When the twist pitch is large, the number of contacts between the twisted wires is reduced, and the electrical resistance can be increased, so that the AC loss due to the coupling current can be reduced.

In the invention according to claim 6, the twist pitch of the primary twisted wire is set to 20 times or less the outer diameter of the superconducting element wire,
The compressive force between the superconducting wires can be increased, the electrical resistance between the primary stranded wires with the smallest twist order can be made extremely small, and the current redistribution and transferability can be improved and stability can be improved. Can be improved.

In the invention according to claim 7, the electrical resistance between the secondary twisted wires and between the tertiary twisted wires can be made small as in the case of the primary twisted wires, and the secondary twisted wires and the tertiary twisted wires can be twisted on the lower order side. It has an effect on the superconducting cable as a wire and can improve the stability.

In the invention of claim 8, the tensile force below the critical load is applied to the higher-order twisted wires to crimp the twisted wires, thereby improving the bonding force between the superconducting strands in the twisted wires. Even if the twist pitch is increased, the electric resistance can be reduced and a highly stable superconducting cable can be obtained.

In the invention of claim 9, the twist pitch Lpn
Is an electrical resistance between the (N-1) -th order twisted wires in the N-th order higher-order twisted wire, which is more than the square of (Lpn / Lp1) of the electric resistance between the superconducting wires of the primary twisted wire of the twist pitch Lp1. Therefore, it is possible to equalize the coupling loss generated in the twisted wires of each order and reduce the AC loss. This superconducting cable takes into consideration that the AC loss due to the coupling current generated between arbitrary superconducting element wires in the cable cross section (conductor cross section) is proportional to the square of the twist pitch ratio.

According to the tenth aspect of the present invention, the high-order twisted wire is heated in an inert gas or vacuum to solid-phase diffusion-bond the twist intersections to form an electrical short-circuit portion. The superconducting wires in the wires are fused to each other, and the electric resistance between the wires can be realized to be extremely small, so that a superconducting cable with high stability can be realized.

According to the eleventh aspect of the present invention, since the electric resistance value of the electric short-circuited portion is set in a range satisfying the conditional expression of [Equation 6], one strand is transferred to the normal conduction state due to disturbance. Even if it does, most of the current can be transferred to a healthy wire that maintains the superconducting state,
It is possible to suppress the Joule heat generation in the wire that has undergone the normal conduction transition and restore it to the superconducting state again, and to greatly improve the stability. In addition to such an advantage of high stability, by clarifying the selection criteria of the electrical resistance value of the electrical short-circuited portion, the practicality can be significantly improved.

According to the twelfth aspect of the present invention, the distance between the electrical short-circuited portions is set within the range satisfying the conditional expressions of [Equation 7] and [Equation 8]. The current flowing through the wires that have undergone the superconducting transition can be quickly transferred within the time, the stability can be greatly improved, and the practicality can be improved by clarifying the selection criteria of the distance between the electrical short-circuited parts. Can be greatly increased.

According to the thirteenth and fourteenth aspects of the present invention, since the twist pitches and the positions of the electrical short-circuiting parts with respect to the high-order twisted wire are clearly defined, the twisted wires of all orders or the minimum necessary orders of twisted wires can be obtained. The stability of can be greatly increased.

According to the fifteenth and sixteenth aspects of the present invention, the twist pitch of the twisted wire is set within a range in which the induced electromotive force caused by the change in the external magnetic field satisfies the condition that it is smaller than the voltage generated at the normal conduction transition. , A sufficiently large transfer current can be obtained even in the presence of current drift due to the coupling current,
The stability can be greatly increased.

In the seventeenth to nineteenth aspects of the invention, since the electrical short-circuit portion is provided in the plural layers of twisted wires arranged in layers, in addition to the same advantages of high stability as described above, high current density can be achieved. Can be realized at the same time.

According to the twentieth aspect of the invention, since the electrical short-circuit portion is formed by lowering the void ratio of the twisted wire, the electrical short-circuit portion can be easily provided in addition to the advantage of high stability as described above. Therefore, it is possible to greatly improve the practicality.

As described above, according to the inventions of claims 11 to 20,
A large amount of current can be transferred from the wire that has undergone the normal conduction transition to the wire that maintains the superconducting state within the time when the cooling performance is maintained, and as a result, the twisted pitch can be applied even when a fluctuating magnetic field is applied to the cable. The induced voltage in both positive and negative directions generated inside can be canceled. Further, high stability can be maintained even if some of the superconducting wires undergo normal transition due to some disturbance.

[Brief description of drawings]

FIG. 1 is a perspective view showing a first embodiment of a superconducting cable according to the present invention.

FIG. 2 is a cable cross-sectional view showing an enlarged cross-section of a superconducting cable.

FIG. 3 is a diagram showing the relationship between the electrical resistance between strands (strands) of each twisted wire provided in the superconducting cable and the twist pitch / strand diameter (strand diameter).

FIG. 4 is a view showing a modified example of the superconducting cable.

FIG. 5 is a perspective view showing another modification of the superconducting cable.

FIG. 6 is a view showing a superconducting cable having a 6 × 6 × 6 type multi-stranded wire structure.

FIG. 7 is a view showing a superconducting cable having a rectangular stranded wire structure.

FIG. 8 is a diagram for explaining a resistance setting example of the second embodiment of the superconducting cable according to the present invention.

FIG. 9 is a schematic circuit diagram illustrating a transfer current between superconducting wires.

FIG. 10 is a graph showing the relationship between the distance between short-circuited portions and the circuit time constant.

FIG. 11 is a schematic perspective view showing a superconducting cable of a first application example.

12A and 12B are schematic perspective views showing a superconducting cable of a second application example.

FIG. 13 is a schematic perspective view showing a superconducting cable of a third application example.

FIG. 14 is a schematic perspective view showing a superconducting cable of a fourth application example.

15A and 15B are diagrams showing a layered superconducting cable of a fifth application example, FIG. 15A is a schematic side view, and FIG. 15B is a schematic sectional view taken along line AA in FIG. 15A.

FIG. 16 is a graph illustrating a setting example of a twist pitch and a conductor diameter of the superconducting cable of the third embodiment.

FIG. 17 is a cable cross-sectional view showing a conventional superconducting cable.

[Explanation of symbols]

 5 Conduit 10, 10A, 10B, 10C Superconducting cable 11 Superconducting element wire 12,25 Primary stranded wire 13,26,33 Secondary stranded wire 14,27 Tertiary stranded wire 16,20 Primary coating material 17,21 Secondary coating material 18 , 22 Tertiary coating material 28,29,30 Reinforcing core wire

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takataro Hamashima 2-4 Suehiro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa Toshiba Keihin Office (72) Inventor Tsutomu Fujioka 1-1-1, Shibaura, Minato-ku, Tokyo Shares Company Toshiba Head Office

Claims (20)

[Claims] 1. A plurality of superconducting wires are twisted together to form a primary twisted wire, and a plurality of these primary twisted wires are twisted together to form a secondary twisted wire. In the superconducting cable configured as described above, the superconducting cable is configured such that the electric resistance value per unit length between twisted wires having the same twist order becomes larger as the twisted wire has a higher twist order. 2. When the final twist order of the high-order twisted wire is N, at least one of the twisted wires having a twist order of (N-1) order or less has a high resistance on the outer surface of the twisted wire. The superconducting cable according to claim 1, wherein a body coating is formed. 3. The superconducting cable according to claim 2, wherein the film of the high-resistor is formed such that the twisted wire having a higher twist order is made thicker than the twisted wire having a lower twist order. 4. The superconducting cable according to claim 2, wherein the coating of the high resistance body is formed of a coating material having a higher electrical resistance in a twisted wire having a higher twist order than in a twisted wire having a lower twist order. 5. The superconducting cable according to claim 1, wherein the twisted wire is set so that the twist pitch increases as the twist order increases. 6. The superconducting cable according to claim 1, wherein the primary stranded wire has a twist pitch Lp1 set within a range of Lp1 ≦ 20d, where d is a diameter of the superconducting wire. 7. The secondary twisted wire has a twist pitch Lp2 set to a range of Lp2 ≦ 30D1 when the diameter of the circumscribed circle of the primary twisted wire is D1, and the tertiary twisted wire is the outer circumference of the secondary twisted wire. When the diameter of the circle is D2, the twist pitch Lp3 is Lp3 ≤ 40
The superconducting cable according to claim 6, wherein the superconducting cable is set in a range of D2. 8. The superconducting cable according to claim 1, wherein after the high-order stranded wire is constructed, a tensile load of a critical load or less is applied to the high-order stranded wire to crimp between the stranded wires. 9. A high-order twisted wire having a twist pitch of Lpn and a twist order of N has an electrical resistance between the (N-1) -th order twisted wires and an electrical resistance between the superconducting wires of the primary twisted wire of the twist pitch Lp1. Of resistance (Lpn /
2. The superconducting cable according to claim 1, wherein the superconducting cable is set to a power of 2 times the power of Lp1). 10. A primary stranded wire is formed by twisting a plurality of superconducting strands, and a plurality of primary stranded wires are stranded to form a secondary stranded wire. Then, the same is sequentially twisted in the same manner to form a higher stranded wire. In the superconducting cable configured as described above, the higher-order twisted wire is heated in an inert gas or vacuum to solid-phase diffusion-bond the twisted intersections to form an electrical short-circuited portion. 11. A twisted wire composed of a plurality of superconducting wires,
In order to make the electric resistance value per unit length of the superconducting element wire at the intersection position of the twisted wire corresponding to an integer multiple of the twist pitch of the twisted wire smaller than the electric resistance value at the position sandwiching the intersection position. An electric short circuit having an electric resistance, the electric short circuit is provided at the intersecting position, and the thermal diffusion distance in the longitudinal direction of the superconducting wire is ld, and the thermal conductivity of the superconducting wire and its When the heat capacities are κ and ρC, and the time when disturbance is applied to the superconducting wire is τq, the thermal diffusion distance ld is given by And the electric resistance value of the electrical short-circuited portion is Rc, the electric resistance value per unit length of the superconducting element wire at the normal conduction transition is Rn, and the superconducting characteristic of the superconducting element wire and When the limiting current value and the critical current value determined by the refrigerant conditions are Ilim and Ic, the electrical resistance value Rc of the electrical short circuit part
Is set to a range that satisfies the conditional expression of 2Rc / (2Rc + Rn × ld) ≦ Ilim / Ic. 12. A stranded wire composed of a plurality of superconducting wires,
An electric resistance for making the electric resistance value per unit length of the superconducting element wire at the positions arranged at regular intervals along the longitudinal direction of the twisted wire smaller than the electric resistance value at the positions sandwiching the arrangement position. And a distance between the electric short-circuited portions is lc, and a thermal diffusion distance in the longitudinal direction of the superconducting element wire is ld, Let Rn be the electric resistance value of the superconducting element wire at the time of the normal conducting transition, Rc be the electric resistance value of the electrical short-circuited portion, and the superconducting element wire that has undergone the normal conducting transition and the superconducting state adjacent to the superconducting element wire. Let L be the leakage inductance per unit length determined by the mutual impedance characteristics of the superconducting wires that are maintained, and the electric resistance value Rn of the superconducting wires and the electric resistance of the electrical short-circuited part. Rc, and circuit time constant determined by the leakage inductance L as a .tau.c, time governing transient heat transfer to the superconducting wire τh
Then, when the thermal diffusion distance ld is smaller than the distance lc between the electrical short-circuited portions (ld <lc), the distance lc between the electrical short-circuited portions is given by When the thermal diffusion distance ld is larger than the distance lc between the electrical short-circuited portions (ld> lc), the distance lc between the electrical short-circuited portions is set as follows: ] A superconducting cable characterized by being set in a range that satisfies the conditional expression of. 13. The twisted wire includes a high-order twisted wire including a primary twisted wire formed by twisting the plurality of superconducting element wires together and a secondary twisted wire formed by twisting the primary twisted wires together. 13. The superconducting wire according to claim 12, wherein each twist pitch is set under the condition that the least common multiple of each twist pitch in each twisted wire of the higher twisted wires is equal to the distance between the electrical short-circuited portions. cable. 14. A twisted wire from the first order to an arbitrary order of the higher order twisted wires when the least common multiple of the respective twist pitches of the higher order twisted wires is larger than the distance between the electrical short-circuited parts. 14. The superconducting cable according to claim 13, wherein the electrical short circuit is provided in the stranded wire from the first order to the arbitrary order when the least common multiple of each twist pitch is smaller than the distance between the electrical short circuits. 15. A superconducting cable having a twisted wire composed of a plurality of superconducting wires, an induced electromotive force caused by a change in an external magnetic field to the superconducting wires, a twist pitch of the twisted wires, and Based on the generated voltage at the time of normal conduction transition of the superconducting element wire, which is determined by one of the longitudinal thermal diffusion distances of the superconducting element wire, the induced electromotive force of the twist pitch is more than the generated voltage. A superconducting cable characterized by being set within a range that satisfies small conditions. 16. The higher twisted wire includes a primary twisted wire formed by twisting the plurality of superconducting wires together and a secondary twisted wire formed by twisting the primary twisted wires together. And the sum of the induced electromotive force for each twisted wire of this higher-order twisted wire, the normal conduction transition determined by one of the twist pitches of the twisted wires of the next order and the thermal diffusion distance. The superconducting cable according to claim 15, wherein each twist pitch is set to a range satisfying a condition that the sum of the induced electromotive forces is smaller than the generated voltage based on the generated voltage at the time. 17. A superconducting cable provided with a stranded wire composed of a plurality of superconducting element wires, wherein the stranded wire is a plurality of stranded wires formed by laying layers at the same pitch in a circumferential direction in which concentric circles have different radii. Yes, an electric value for reducing the electric resistance value per unit length of the superconducting element wire at each crossing position corresponding to the twist pitch of the twisted wires of the plurality of layers below the electric resistance value at the position sandwiching the crossing position. A superconducting cable characterized in that an electrical short-circuit portion having a resistance is provided at the intersecting position. 18. The superconducting cable according to claim 17, wherein the twisting directions of the twisted wires of two adjacent layers among the twisted wires of the plurality of layers are set to be opposite to each other. 19. The superconducting cable according to claim 18, wherein the number of the plurality of layers is an even number. 20. A conduit for accommodating the twisted wire is further provided, and the electrical short-circuit portion is provided with means for reducing a void ratio of the twisted wire orthogonal to an axial direction of the conduit at the intersecting position. The superconducting cable according to any one of 17 to 19.