JP3286036B2 - Forced cooling type superconducting conductor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a supercooled superconducting conductor used for a superconducting coil for generating a high magnetic field used for nuclear fusion or energy storage.

[0002]

2. Description of the Related Art In a superconducting coil for generating a high magnetic field,
A large electromagnetic force acts due to the interaction between the high magnetic field generated from the coil and the coil current. For this reason, a forced cooling type superconducting conductor having excellent mechanical strength is employed as the superconducting conductor.

As a conventional forced cooling type superconducting conductor, for example, there is one having a configuration as shown in FIG. In FIG. 4, reference numeral 1 denotes a superconducting element wire in which a superconducting filament is disposed on a stabilizing material matrix such as copper, and further, an insulating film is provided on the surface thereof. have.

[0004] The primary stranded wire 2 is formed by twisting three superconducting strands 1, the secondary stranded wire 3 is formed by stranded three primary stranded wires 2, and the secondary stranded wire 3 is formed by three stranded wires. It is 3
The fourth stranded wire 5 is formed by stranded two tertiary stranded wires 4 of the next stranded wire 4. A forced cooling type superconducting conductor is constituted by further arranging six stranded quaternary wires 5 in this manner and placing them in a conduit 6.

[0005] The reason why the superconducting wire is multi-core and multi-stranded is to aim at high critical current and low AC loss as the superconducting conductor. In addition, conduit 6
The gap other than the internal superconducting wire is used as a flow path of cryogenic helium for cooling.

[0006]

The critical current value of the superconducting conductor constructed as described above should originally be given by (critical current value per superconducting wire) × (number of superconducting wires). is there. However, actually, in order to reduce the AC loss, the surface of the superconducting wire is provided with an insulator such as chromium or formalin coating.

For this reason, a drift occurs between the superconducting wires due to a difference in connection resistance of the conductor connecting portion and the like, and quench occurs in some superconducting wires, so that only a critical current value smaller than the above value is obtained. I can't get it. In addition, there is another problem that the cooling efficiency is poor and the stability margin is not sufficient, so that the current limit is low and the current cannot flow up to the critical current value.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and suppresses a drift generated between superconducting wires of a multi-core stranded wire, promotes a branch flow, and reduces a cooling efficiency (stability margin). It is an object of the present invention to provide a forced cooling type superconducting conductor capable of improving the critical current value and the limiting current value.

[0009]

According to the present invention, in order to achieve the above-mentioned object, in order to suppress a drift generated between superconducting wires of a multi-core stranded wire and to promote a branch flow, a pitch of the superconducting wires is increased. Provide a non-insulating part on the surface of the superconducting wire with no insulation film at the above intervals, and make electrical contact with the adjacent superconducting wire.
Let

[0010]

In the forced cooling type superconducting conductor, the value of the current flowing through each superconducting element wire of the multifilamentary stranded wire at the beginning of energization is determined by the connection resistance of the conductor connection part, and when the coil current is increased, one of the superconducting The strand approaches the critical current value of the strand. As the critical current value is approached, the superconducting wire gradually generates a very small resistance. The redistribution of the current is caused by the shunt between the superconducting wires due to the generation of the resistance, and an attempt is made to make the current uniform.

In the conventional superconducting wire, the insulating coating is applied over the entire length, so that the shunting is performed retroactively to the conductor connecting portion, and the inductance of the circuit becomes considerably larger than the resistance. For this reason, the time constant of the shunt is considerably large, and it is impossible to compensate for the increase in the coil current value.

In the forced cooling type superconducting conductor according to the present invention, the insulating coating of the superconducting wire is not uniform in the longitudinal direction, and the insulating coating is not provided on the surface of the superconducting wire at intervals of the stranded wire pitch or more. An insulating portion is provided, and is in electrical contact with an adjacent superconducting element wire. For this reason, the circuit length of the shunt can be significantly reduced, and the shunt time constant can also be reduced, so that the shunt can be performed at a speed exceeding the rise in the coil current value.

Therefore, the critical current value can be increased to the theoretical value of the critical current value of the superconducting conductor, ie, (the critical current value per one superconducting wire) × (the number of superconducting wires). On the other hand, by setting the pitch of the non-insulating portions to be equal to or longer than the pitch of the stranded wire, it is possible to almost eliminate an increase in AC loss.

Further, by providing irregularities on the surface of the superconducting wire, the cooling area of the superconducting wire can be increased.
The cooling efficiency as a conductor, that is, the stability margin is increased, and the current limiting value of the superconducting conductor can be improved.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an external view of a superconducting element wire according to a first embodiment of the present invention, in which a superconducting element wire is twisted. FIG.
As shown in the figure, the superconducting wires 1a, 1b, 1c are twisted at a twisted wire pitch lp in a bundle of three wires. The surfaces of these superconducting wires 1a, 1b, 1c are electrically in contact with each other at a non-insulating portion 7 indicated by hatching. The other surfaces are insulated by chrome plating or the like. In this case, the pitch L of the non-insulating portion is set to be larger than the twisted wire pitch lp.

In the forced cooling type superconducting conductor having such a configuration, when the current value at the time of energization is increased, one of the superconducting wires 1a becomes critical as the wire due to the drift between the wires as described above. It approaches the current value. Further, as the current approaches the critical current value, an extremely small resistance is gradually generated in the superconducting wire 1a. At this time, the superconducting wire 1
Since the surfaces of a, 1b, and 1c are electrically in contact with each other at the non-insulating portion 7 shown by hatching, the current of the superconducting element wire 1a contacts through the non-insulating portion 7 due to the generation of resistance. To the superconducting element wires 1b and 1c,
The current is equalized.

Therefore, the adjacent superconducting wires are in electrical contact with each other at a shorter interval than the superconducting conductor length.
Since the circuit length of the shunt can be significantly reduced, and the shunt time constant can also be reduced, the shunt can be performed at a speed exceeding the rise in the coil current value. Thereby, the critical current value can be increased to the theoretical value of the critical current value as the forced cooling type superconducting conductor (critical current value per superconducting wire) × (number of superconducting wires). On the other hand, by setting the pitch L of the non-insulating portion to be equal to or more than the twisted wire pitch lp,
Almost no increase in AC loss can be eliminated.

FIG. 2 is an external view of a forcedly cooled superconducting conductor according to a second embodiment of the present invention in which a primary stranded wire is stranded. In the present embodiment, in the case of the multiply twisted forced cooling type superconductor, after performing the processing shown in FIG. 1 on the primary strand, as shown in FIG. 2, the primary strands 2a, 2b, 2c Similarly, by setting the pitch L of the non-insulating portions to be equal to or longer than the stranded wire pitch lp and electrically contacting adjacent primary wires in the non-insulating portion 7, the same effect as described above can be obtained.

FIG. 3 is a sectional view of a forced cooling type superconducting conductor showing a third embodiment of the present invention. The configuration of the superconducting conductor in this embodiment is the same as the conventional one, but the primary stranded wire 2 is formed by stranded three superconducting wires 8 having irregularities on the surface.
However, three primary strands 2 are twisted to form a secondary strand 3
However, three stranded wires 3 are twisted to form a third stranded wire 4
However, a quaternary stranded wire 5 is formed by stranded two tertiary stranded wires 4.

The quaternary stranded wire 5 configured as described above is further twisted into six wires and housed in a conduit 6. According to the third embodiment, since the surface is provided with irregularities, the cooling area of the superconducting wires 1a, 1b, 1c is larger than that of a superconducting wire having a normal cross-sectional shape. Therefore, the cooling efficiency as a conductor, that is, the stability margin is increased, so that the current limit value of the superconducting conductor can be improved.

[0021]

As described above, according to the present invention, the drift generated between the superconducting wires of the multi-core stranded wire is suppressed, the branch current is promoted, and the cooling efficiency (stability margin) is improved.
It is possible to provide a forced cooling type superconducting conductor capable of improving a critical current value and a limited current value.

[Brief description of the drawings]

FIG. 1 is an external view in which a superconducting element wire in a first embodiment of a forced cooling type superconducting conductor according to the present invention is twisted.

FIG. 2 is an external view in which a superconducting element wire according to a second embodiment of the present invention is twisted.

FIG. 3 is an external view of a stranded superconducting element wire according to a third embodiment of the present invention.

FIG. 4 is a sectional view showing a conventional forced cooling type superconducting conductor.

[Explanation of symbols]

1a, 1b, 1c ... superconducting wires, 2a, 2b, 2c ...
… Primary stranded wire, 3… secondary stranded wire, 4… tertiary stranded wire, 5…
4th stranded wire, 6 ... conduit, 7 ... non-insulating part, 8 ...
A superconducting element wire having an uneven portion. lp ... stranded wire pitch, L ...
... Pitch of non-insulating part.

Claims (2)

(57) [Claims] 1. A superconducting filament is arranged on a stabilizing material matrix such as copper, and a superconducting element wire having an insulating film provided on its surface is multi-stranded and multi-stranded, and this is arranged inside a conduit. In the configured forced cooling type superconductor,
Ultra wherein in twisted pitch or spacing of the superconducting wire is provided a non-insulating portion is not provided with an insulating film on the surface of the superconductor element, adjacent
A forced cooling type superconducting conductor characterized by being electrically contacted with a conductive wire . 2. The forced cooling type superconducting conductor according to claim 1, wherein irregularities are provided on the surface of the superconducting element wire.