JPH10326915A - Connection structure of superconductive wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the normal conductive transition of a superconductive coil due to generated heat on the normal conductive transition of a persistent current switch, by providing a superconductive connection conductor with a high critical current at the superconductive wire contact of the superconductive coil and the persistent current switch. SOLUTION: An opening/closing switch 8 is closed when taking out a storage energy externally, and a persistent current switch 7 is shifted to a normal conductive state. At this time, the resistance of the switch 7 increases, thus generating Joule loss heat. The heat is transferred to a permanent current switch conductor 3, thus increasing the temperature of the conductor 3. However, a superconductive connection conductor 1 with a higher critical temperature than the conductors is installed at the connection between the superconductive coil conductor 2 and the conductor 3 while it is in direct contact with both conductors. And, the temperature of the conductors 2 and 3 increases at the connection and current flows through the conductor 1 as far as the conductor 1 does not cause normal conductive transition even if the normal conductive state results. Therefore, current flowing to the side of the switch 7 decreases, thus suppressing amount of heat being generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connection structure between a superconducting wire of a superconducting coil used for a superconducting energy storage device and the like and a superconducting wire of a permanent current switch.

[0002]

2. Description of the Related Art A superconducting energy storage device realizes a permanent current circuit by combining a superconducting magnet and a permanent current switch. Generally, a superconducting magnet and a permanent current switch are connected in parallel, and this parallel circuit is used. Is connected to a desired power supply via a power lead.

FIGS. 3 to 5 are schematic views showing an example of a superconducting energy storage device having such a configuration. In the drawings, reference numeral 21 denotes a superconducting coil, 22 denotes a permanent current switch, 23 denotes a power lead, and 23 denotes a power lead. Reference numeral 24 denotes an open / close switch, and reference numeral 25 denotes an AC / DC converter. A superconducting coil 21 and a permanent current switch 22 are connected in parallel, an AC / DC converter 25 is connected to this circuit via a power lead 23 and an open / close switch 24, and an AC power supply system (not shown) is connected to the AC / DC converter 25. This constitutes a superconducting energy storage device. Each of the superconducting coil 21 and the permanent current switch 22 is formed of a superconductor that transitions to a superconducting state at an extremely low temperature, and is cooled by a refrigerant such as liquid helium.

Power can be stored by operating the superconducting energy storage device shown in FIGS. 3 to 5 according to the following procedure. As shown in FIG. 3, the permanent current switch 22 is turned off in a state where the open / close switch 24 is closed, and a current is caused to flow through the superconducting coil 21.
Electric power is stored in the superconducting coil 21 as magnetic energy. Next, the permanent current switch 22 is turned on by setting it to a superconducting state, and the current from the outside is reduced, and the current flows into the permanent current switch 22. When the current from the outside becomes zero, a current equivalent to the current flowing through the superconducting coil 21 flows through the permanent current switch 22, and a permanent current mode is set. When the open / close switch 24 is opened in this state, since the electric resistance of both the superconducting coil 21 and the permanent current switch 22 is zero, the current becomes a permanent current and does not attenuate in this closed circuit as shown in FIG. It continues to flow, and the energy stored in the superconducting coil 21 is stored without loss.

In order to extract the stored energy, the permanent current switch 22 is turned off by closing the open / close switch 24 and then bringing the permanent current switch 22 into the normal conduction state as shown in FIG. Then, the energy stored in the closed circuit including the superconducting coil 21 and the permanent current switch 22 can be taken out through the power lead 23 as electric power.

In a superconducting energy storage device as shown in FIGS. 3 to 5, a superconducting coil 21 and a permanent current switch 2
In the superconducting state, it is necessary to make the resistance of the closed circuit formed from 2 as close to zero as possible. The problem at this time is the connection between the superconducting coil 21 and the permanent current switch 22. Conventional superconducting energy storage devices often employ a method as shown in FIG. 6 in order to reduce electric resistance as much as possible.

FIG. 6 shows a conventional superconducting coil 21 and a permanent electric coil.
It is a schematic diagram showing an example of a connection method of the flow switch 22,
In the figure, reference numeral 31 is a copper wire, reference numeral 32 is a superconducting coil conductor,
Reference numeral 33 denotes a permanent current switch lead, and reference numeral 34 denotes a solder layer.
is there. As shown in FIG. 6, a superconducting coil
Lead 32 and permanent current switch lead 33
Wrap so that they are in close contact with each other.
Cover layer 34. This superconducting coil conductor 32 and
The connection part of the permanent current switch conductor 33 is 20 to 30 cm.
By increasing the length as described above, the resistance of the connection portion can be reduced to 10 ^-8Ohm
Can be reduced.

In the above-described superconducting energy storage device, the characteristics required for the permanent current switch 22 include a normal conduction state, that is, a high resistance value when the switch is turned off, and a superconducting state, that is, a state in which the switch is turned off. One example is that a large amount of current can flow when turned on. For this reason, in FIG. 5, when the permanent current switch 22 is shifted from the superconducting state to the normal conducting state, the permanent current switch 22 generates heat due to Joule loss. This heat is transmitted to the superconducting coil 21 through the superconducting wire, thereby increasing the temperature of the superconducting coil 21. If the calorific value is large, the superconducting coil 2
The critical temperature of the superconducting coil 21 may exceed the critical temperature of 1 and cause a normal conduction transition (quenching) of the superconducting coil 21.

[0009]

SUMMARY OF THE INVENTION In view of the above, the present invention relates to a superconducting energy storage device in which a superconducting coil causes a normal conduction transition due to heat generated when a permanent current switch causes a normal conduction transition. The purpose is to prevent.

[0010]

An object of the present invention is to provide a superconducting connecting conductor having a higher critical temperature than any of the above superconducting wires at a portion where the superconducting wire of the superconducting coil and the superconducting wire of the permanent current switch are in direct contact. Can be solved by setting them so that they are in direct contact with each other.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing an example of an embodiment of the present invention. In the figure, reference numeral 1 denotes a superconducting connection conductor, reference numeral 2 denotes a superconducting coil conductor, reference numeral 3 denotes a permanent current switch conductor, reference numeral 4 denotes a copper wire, and reference numeral 5 denotes a conductor. Is a solder layer. As shown in FIG. 1, the superconducting coil conductor 2 and the permanent current switch conductor 3 are connected, and the superconducting connection conductor 1 is installed at the connection portion so as to directly contact the superconducting coil conductor 2 and the permanent current switch conductor 3. With the copper wires 4 in contact with these, the entire connection portion is covered with a solder layer 5 and fixed.

FIG. 2 is a schematic configuration diagram showing an example of a superconducting energy storage device made by using an example of the embodiment of the present invention shown in FIG. 1 for a connection portion. Reference numeral 7 denotes a permanent current switch, reference numeral 8 denotes an open / close switch, and reference numeral 9 denotes an AC / DC converter. When energy is stored, that is, when a closed circuit is formed by superconducting coil 6 and persistent current switch 7 and superconducting coil 6 and persistent current switch 7 are in a superconducting state, superconducting coil conductor 2 and persistent current switch conductor 3
Is also in the superconducting state, and the current continues to flow in the closed circuit formed by the superconducting coil 6 and the permanent current switch 7.

When the stored energy is taken out to the outside, the open / close switch 8 is closed and the permanent current switch 7 is shifted to the normal conduction state. At this time, the resistance value of the permanent current switch 7 becomes high, and Joule loss occurs. The accompanying heat is generated.
This heat propagates through the permanent current switch lead 3 and raises the temperature of the permanent current switch lead 3. However, a superconducting connection conductor 1 having a higher critical temperature than those of the superconducting coil conductor 2 and the permanent current switch conductor 3 is installed at a connection portion between the superconducting coil conductor 2 and the permanent current switch conductor 3 so as to be in direct contact with both conductors. In, even if the temperature of the superconducting coil conductor 2 or the permanent current switch conductor 3 rises and transitions to the normal conduction state, as long as the superconducting connection conductor 1 does not cause a normal conduction transition, current flows through the superconducting connection conductor 1. Can flow. For this reason, when the permanent current switch 7 makes a transition to normal conduction, the temperature of the connection portion between the superconducting coil conductor 2 and the permanent current switch conductor 3 rises, and even if these conductors make transition to normal conduction, the current is Since it is possible to preferentially flow to the superconducting coil 6 through the superconducting connection conductor 1 that has not yet transitioned to the normal conduction state, the permanent current switch 7 is closer to the side of the permanent current switch 7 than when the superconducting connection conductor 1 is not juxtaposed. The flowing current is reduced, and the amount of heat generated as a result can be suppressed. Thereby, switching of the permanent current switch 7 and the open / close switch 8 can be performed stably.

The superconducting connection conductor 1 comprises a superconducting coil conductor 2
It is sufficient that the superconducting state can be maintained even at a temperature at which the permanent current switch conductor 3 undergoes a normal conduction transition. Therefore, a material whose critical temperature is higher than the critical temperatures of the superconducting coil conductor 2 and the permanent current switch conductor 3 is appropriately used. Can be. Also, the larger the difference between the critical temperatures of the superconducting connection conductor 1, the superconducting coil conductor 2 and the permanent current switch conductor 3, the wider the safety range becomes, which is more preferable. The superconducting connection conductors 1 that can be suitably used include compound superconductors such as Nb ₃ Sn wire and Nb ₃ A
1-wire material, V ₃ Ga wire, etc., oxide-based superconductors such as yttrium-based superconductors and bismuth-based superconductors, and highly stabilized superconducting wires such as Al-stabilized wires having an Al ratio of 1.0 or more, and Cu ratios of 1. Zero or more Cu-stabilized wires can be exemplified.

The connecting portion of the superconducting connection conductor 1, the superconducting coil conductor 2 and the permanent current switch conductor 3 may have any structure as long as the respective superconductors are closely connected. For example, if each of these superconductors is composed of a stranded wire, the stranded wire is loosened at the connection portion of each superconductor, and connected so as to be entangled with other superconductors, so that the area in direct contact Can be increased. In addition, it is preferable that the entire length of the superconducting connection conductor 1 be as long as possible, because a current flow path can be secured and the resistance of the connection portion can be suppressed low. It is preferable that at least the total length of the superconducting connection conductor 1 be longer than the total length of the connection portion between the superconducting coil conductor 2 and the permanent current switch conductor 3. The connecting portion of the above-described superconducting connecting conductor 1, superconducting coil conducting wire 2 and permanent current switch conducting wire 3 is unlikely to be affected by a magnetic field unlike a conventional connection structure, and therefore may be provided in a magnetic field. .

[0016]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples.

Example 1 A superconducting energy storage device as shown in FIG. 7 was prepared. That is, an yttrium-based superconductor was used as the superconducting connection conductor 41, and a thermal permanent current switch was used as the permanent current switch 42. The superconducting coil 43 was cooled with liquid helium to be in a superconducting state, and a current was passed through the superconducting coil 43 through the conducting wire 44. The permanent current switch 42 is cooled and brought into a superconducting state to be turned on, and the current from the outside is reduced and the current is caused to flow to the permanent current switch 42, thereby comprising the permanent current switch 42 and the superconducting coil 43. Stored energy in a closed circuit. Next, when the heater 45 is heated to cause the permanent current switch 42 to transition to the normal conduction state, the conductor is also heated by the generated heat, and this heat is transmitted through the conductor, so that the conductor closer to the permanent current switch 42 The normal conduction transition occurred in the order from the lead wire. The normal conduction transition reached the connection between the conducting wire and the superconducting connection conductor 41, but the superconducting coil 43 was able to maintain the superconducting state and release energy to the outside. The normal conduction transition of the conductor was determined by placing two taps at an arbitrary position on the conductor and measuring the potential difference between the taps. That is, in the superconducting state, the potential difference is almost zero, and a transition to normal conduction causes a potential difference.

Embodiment 2 A superconducting energy storage device as shown in FIG. 8 was prepared. That is, a highly stabilized Nb ₃ Sn conductor was used as the superconducting connection conductor 51, and a magnetic field type permanent current switch was used as the permanent current switch 52. The superconducting coil 53 is cooled with liquid helium to be in a superconducting state,
A current was supplied to the superconducting coil 53 through the conducting wire 54. By stopping the control magnet 55, the permanent current switch 52 is transited to the superconducting state, the current from the outside is reduced, and the current is supplied to the permanent current switch 52, so that the permanent current switch 52 and the superconducting coil 53 Energy was stored in a closed circuit constructed. Next, the permanent magnet switch 52 is operated by operating the control magnet 55.
Was changed to the normal conducting state, but the superconducting coil 53 was able to maintain the superconducting state and release energy to the outside.

[0019]

As described above, the superconducting wire connection structure of the present invention has a critical temperature higher than that of any of the above superconducting wires at a portion where the superconducting wire of the superconducting coil and the superconducting wire of the permanent current switch are in direct contact. High superconducting connection conductors, so that they are in direct contact with each other,
In the connection portion of the superconducting wire, even if the temperature of the superconducting wire rises due to the normal conduction transition of the permanent current switch, the superconducting connection conductor keeps the superconducting state and can suppress the propagation of heat in the superconducting wire. The total length of the superconducting connection conductor
By making the length of the connection portion of the superconducting wire longer than the entire length, the resistance of the connection portion can be suppressed low and a current flow path can be secured. As the superconducting connection conductor, any of compound superconductors, oxide superconductors, and highly stabilized superconducting wires can be suitably used. Also, the connection portion of the superconducting connection conductor 1, the superconducting coil conductor 2 and the permanent current switch conductor 3 is unlikely to be affected by a magnetic field, unlike the conventional connection structure, and therefore may be provided in a magnetic field. .

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing an example of a superconducting energy storage device created by using an example of an embodiment of the present invention for a connection portion.

FIG. 3 is a schematic view showing an example of a superconducting energy storage device.

FIG. 4 is a schematic view showing an example of a superconducting energy storage device.

FIG. 5 is a schematic view showing an example of a superconducting energy storage device.

FIG. 6 is a schematic diagram showing an example of a conventional connection method between a superconducting coil and a permanent current switch.

FIG. 7 is a schematic view showing a superconducting energy storage device according to the first embodiment.

FIG. 8 is a schematic diagram illustrating a superconducting energy storage device according to a second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Superconducting connection conductor, 2 ... Superconducting coil conductor, 3 ... Permanent current switch conductor, 4 ... Copper wire, 5 ... Solder layer

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Shoji Iwasaki, Inventor 1-5-1, Kiba, Koto-ku, Tokyo Inside Fujikura Co., Ltd. (72) Inventor Nobuyuki 1-15-1, Kiba, Koto-ku, Tokyo Stock Inside Fujikura (72) Inventor Takashi Saito 1-5-1, Kiba, Koto-ku, Tokyo Inside Fujikura (72) Inventor Jin Homma 7-2-1, Nakayama, Aoba-ku, Aoba-ku, Sendai City, Miyagi Prefecture Tohoku Electric Power Company Stock Inside the company R & D center

Claims (3)

[Claims] A superconducting connection conductor having a higher critical temperature than any of the above superconducting wires is provided at a portion where the superconducting wire of the superconducting coil is in direct contact with the superconducting wire of the persistent current switch.
A superconducting wire connection structure which is installed so as to be in direct contact with each other. 2. The superconducting wire connection structure according to claim 1, wherein the total length of the superconducting connection conductor is longer than the total length of the direct contact portion of the superconducting wire. 3. The superconducting wire connection structure according to claim 1, wherein the superconducting connection conductor is made of one of a compound superconductor, an oxide superconductor, and a highly stabilized superconducting wire. .