JPH10335711A - Permanent electric current switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a continuous operation even it a quench occurs at a contact point made of super metallic member by an electrode being provided with a second contact point made of high purity metallic member having a lower resistance than a resistance of the super metallic member while the quench occurs. SOLUTION: Switching-on and opening operation of a movable electrode 1 is performed by a driving mechanism and a superconductive contact point (a first contact point) is formed by superconductive members 2 and 4 contacting each other caused by the movable electrode 1 and a fixed electrode 3. Then a second contact point is also formed by high purity metallic members 10 and 11 contacting each other. By the way if an electric current through the first contact point is over 600 (A), a quench occurs by a contact point resistance suddenly increasing. On the other hand the second resistance of the same high purity metal is constant without depending upon an electric current value. Therefore even if the quench occurs at the first contact point, electric current flows through the second contact point because a resistance of the second contact point becomes less and a continuous operation is possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permanent current switch used for operating a superconducting coil with a permanent current.

[0002]

2. Description of the Related Art FIG. 10 shows, for example, Japanese Patent Publication No. 55-8826.
FIG. 1 is a cross-sectional view showing a conventional permanent current switch disclosed in Japanese Unexamined Patent Application Publication No. H10-115,004. In the drawing, 1 is a movable electrode made of a high-purity metal member such as copper or silver, 2 is a superconducting metal member such as an Nb-Ti alloy used as a contact of the electrode, 3
Is a fixed electrode made of a high-purity metal member like the movable electrode 1, 4 is a superconducting metal member used as a contact of the electrode like the superconducting metal member 2, 5 is a movable electrode side metal cover, 6 is a movable electrode side metal cylinder, 7 is a bellows, 8 is a ceramic insulating cylinder, and 9 is a fixed electrode side metal cylinder.

One end of the bellows 7 is hermetically fixed to the movable electrode 1, and the other end is hermetically fixed to the insulating cylinder 8 via the movable electrode side metal cover 5 and the movable electrode side metal cylinder 6. On the other hand, the fixed electrode 3 side is also hermetically fixed to the insulating tube 8 via the fixed electrode side metal tube 9. As a result, the permanent current switch becomes an airtight container, and the inside thereof is evacuated to a vacuum. Thus, by placing the movable electrode 1 and the fixed electrode 3 in a vacuum, impurities and oxide films do not adhere to the surfaces of the contacts made of the superconducting metal members 2 and 4, so that the variation in the contact resistance value can be suppressed.

The permanent current switch needs to be in a very low temperature state in order to maintain the superconducting state, and is cooled by liquid helium (not shown), a refrigerator or the like.

The movable electrode 1 is turned on and off by a drive mechanism (not shown), and the movable electrode 1 and the fixed electrode 3 are moved.
And the superconducting metal members 2 and 4 contact each other to form a superconducting contact.

[0006]

As described above, in the conventional permanent current switch, although the superconducting metal members 2 and 4 are in contact with each other to form a contact, a very small contact resistance can be obtained. When a disturbance such as a change in the current value occurs, a phenomenon that the contact resistance value of the superconducting metal members 2 and 4 rapidly rises and the superconducting metal member is not in the superconducting state, that is, a quench occurs.

FIG. 11 is a characteristic diagram showing the relationship between the current flowing when the permanent current switch shown in FIG. 8 is turned on and the contact resistance of the superconducting metal members 2 and 4. As shown in the figure, the superconducting state is maintained until the conduction current I is around 600 (A), and the contact resistance R maintains a low value of 2 × 10 ⁻⁹ ohm (Ω). It can be seen that when the resistance exceeds 600 (A), the contact resistance R sharply rises to about 2 × 10 ⁻⁵ ohm (Ω) and quench occurs.

When the quench occurs, the resistance value rises rapidly, so that the calorific value of the electrode contacts increases and the temperature rises.
For example, when the permanent current switch is set to a conduction current I = 1000
If you want to drive raised to (A), the heating value of the contact of the electrode Q (W) from ^{Q = I 2 R, Q =} 1000 2 × 2 ×
It is as large as 10 ⁻⁵ = 20 (W). Therefore, the amount of evaporation of liquid helium for keeping the persistent current switch in a cryogenic state is large, and the load on the refrigerator is too large, which makes it difficult to continue the operation of a device such as a superconducting coil equipped with the persistent current switch. There was a problem.

Further, in the conventional permanent current switch, since the operation of the movable electrode 1 when moving during opening and closing is not particularly restricted, the contact surfaces of the superconducting metal members 2 and 4 are
There has been a problem that the contact resistance varies with each operation.

Further, in the conventional permanent current switch, the electrodes are placed in a vacuum to prevent the contact surfaces of the superconducting metal members 2 and 4 from being stained. Since sparks are generated, there is still a problem that dirt adheres to the sparks.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a permanent current switch capable of continuing operation even when a contact made of a superconducting metal member is quenched. It is another object of the present invention to obtain a permanent current switch that suppresses a variation in the contact resistance value of the contact at the time of closing. It is another object of the present invention to provide a permanent current switch that suppresses the occurrence of sparks at the contacts.

[0012]

SUMMARY OF THE INVENTION A permanent current switch according to the present invention includes a pair of electrodes which are arranged so as to be able to freely contact and separate from each other, and uses a superconducting metal member as a first contact of the pair of electrodes. In the above, the pair of electrodes includes a second contact made of a high-purity metal member having a resistance lower than the resistance when the superconducting metal member is quenched.

The second contact is a slider that slides on the outer surface of the electrode during opening and closing operations of the electrode and opens after the first contact.

Further, one of the pair of electrodes is provided with a space and the other is provided with a second contact. The second contact slides on the inner surface of the space when the electrode is opened and closed and opens later than the first contact. It is an extreme slider.

A guide groove is provided on the outer surface of the electrode, and the slider slides in the guide groove.

A guide groove is provided on the inner surface of the space, and the slider slides in the guide groove.

The surface of the guide groove that contacts the slider is a superconducting metal member.

The surface of the guide groove that contacts the slider is a high-purity metal member.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. The major difference between the present invention and the conventional example is that the second contact is formed by using a high-purity metal member having a resistance lower than the resistance when the superconducting metal member used for the contact of the electrode of the persistent current switch is quenched. Is to form

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a permanent current switch according to Embodiment 1 of the present invention. In the figure, reference numeral 1 denotes a movable electrode made of a high-purity metal member such as copper or silver,
2 is used as a first contact of the electrode, for example, Nb-T
A superconducting metal member such as an i-alloy, 3 is a fixed electrode made of the same high-purity metal member as the movable electrode 1, 4 is a superconducting metal member also used as a first contact of the electrode, 5 is a movable electrode side metal cover, 6 is Movable electrode side metal cylinder, 7 is bellows, 8
Is a ceramic insulating cylinder, 9 is a fixed electrode side metal cylinder, 10
And 11 are high-purity metal members as second contacts of the electrodes.

One end of the bellows 7 is hermetically fixed to the movable electrode 1, and the other end is hermetically fixed to the insulating cylinder 8 via the movable electrode side metal cover 5 and the movable electrode side metal cylinder 6. On the other hand, the fixed electrode 3 side is also hermetically fixed to the insulating tube 8 via the fixed electrode side metal tube 9. As a result, the permanent current switch becomes an airtight container, and the inside thereof is evacuated to a vacuum. By placing both electrodes in a vacuum in this manner, since impurities and oxide films do not adhere to the first contact surfaces formed by the superconducting metal members 2 and 4, variations in contact resistance can be suppressed.

Next, the operation will be described. The closing and opening operations of the movable electrode 1 are performed by a driving mechanism (not shown), and the movable electrode 1 and the fixed electrode 3 are closed.
The superconducting metal members 2 and 4 are in contact with each other to form a superconducting contact (first contact). At this time, the high-purity metal members 10 and 11 come into contact with each other to form a second contact. Thus, even if the first contacts of the superconducting metal members 2 and 4 are quenched, a current can be passed to the second contacts of the high-purity metal members 10 and 11.

FIG. 2 is a diagram showing the current flowing when the permanent current switch according to the first embodiment of the present invention is turned on, the resistance value (solid line) of the first contact by the superconducting metal members 2 and 4, the high-purity metal member 10 and FIG. 11 is a characteristic diagram illustrating a relationship with a resistance value (broken line) of a second contact according to FIG. Here, the superconducting metal members 2 and 4 are made of Nb-Ti alloy, high-purity metal material 1
Copper is used for 0 and 11, respectively.

As shown in the figure, the resistance value of the first contact is
The contact current R is in a superconducting state until the current I is around 600 (A), and the contact resistance R maintains a low value of 2 × 10 ⁻⁹ ohm (Ω), but the current I exceeds 600 (A). And the contact resistance R sharply rises to about 2 × 10 ⁻⁵ ohms (Ω), and quenching occurs as in the above-described conventional example. On the other hand, the resistance value R of the second contact, which is the same high-purity metal member, is 5 × 1 regardless of the magnitude of the flowing current I.
It is constant at about ^0-7 ohms (Ω). Therefore, when the first contact is quenched, the resistance value of the second contact becomes lower, so that the current flows to the second contact. As described above, even if the first contact is quenched, it is possible to pass a current through the second contact. In addition, the amount of heat generated at the second contact is small.

For example, the permanent current switch is set to a current I =
When the operation is to be performed with the temperature increased to 1000 (A), the heat value Q (W) of the second contact is calculated from Q = I ² R and Q = 1000.
² × 5 × 10 ⁻⁷ = 0.5 (W). With this value, the amount of evaporation of liquid helium to keep the cryogenic state of the permanent current switch is small, and the load on the refrigerator is small, so even if the first contact is quenched, the permanent current switch is mounted The operation of the device such as the superconducting coil can be continued.

In FIG. 1, the high-purity metal member 10
And 11 show only two pairs,
If a large number are arranged around the movable electrode 1 and the fixed electrode 3, the effect of further reducing the resistance value of the second contact can be obtained although the outer shape of the permanent current switch becomes large.

In the first embodiment, the high-purity metal members 10 and 11 as the second contacts are made of copper. However, the resistance value when the superconducting members 2 and 4 are quenched is lower. As long as it has a high-purity metal material, different materials may be used for the high-purity metal members 10 and 11. A high-purity metal member used for the movable electrode 1 and the fixed electrode 3 and high-purity metal members 10 and 1 as second contacts
1 may be the same material or different materials.

Embodiment 2 FIG. 3 is a sectional view showing a permanent current switch according to Embodiment 2 of the present invention. In the figure, 100 is a slider made of a high-purity metal member, 1
Reference numeral 10 denotes a slider base made of a high-purity metal member.

Next, the operation will be described. The closing and opening operations of the movable electrode 1 are performed by a driving mechanism (not shown), and the movable electrode 1 and the fixed electrode 3 are closed.
The superconducting metal members 2 and 4 are in contact with each other to form a superconducting contact (first contact). At this time, the slider 1
00 slides on the outer surface of the movable electrode 1 to form a second contact.

By adopting such a configuration, in the opening operation of the permanent current switch, even if the first contacts of the superconducting metal members 2 and 4 are separated, the second contacts of the slider 100 and the movable electrode 1 are separated. Are still in contact with each other, so that the occurrence of a spark at the first contact point due to the current flow is suppressed. Therefore, the first contact is not stained, and the variation in the resistance value at the first contact can be suppressed. In addition, since the operation of the movable electrode 1 is guided by the slider 100, the contact surfaces of the first contacts by the superconducting metal members 2 and 4 can always be brought into contact on the same surface, and the resistance value varies. Can be suppressed.

In the second embodiment, the fixed electrode 3
The slider 100 and the slider base 110 are provided on the side, and the slider 100 is configured to slide on the outer periphery of the movable electrode 1. However, as shown in FIG. The slider 100 and the slider base 110 may be provided so that the slider 100 slides on the outer periphery of the fixed electrode 3.

Embodiment 3 FIG. FIG. 5A is a cross-sectional view showing a permanent current switch according to Embodiment 3 of the present invention. FIG. 5B is a cross-sectional view taken along dashed-dotted line XY in FIG. FIG. In the figure, 12
Is a guide groove in which the sliding portion of the slider 100 is formed on the outer surface of the movable electrode 1. Slider 100 has guide groove 12
Slide along. Here, an airtight container portion including the insulating cylinder 8 and the like is omitted.

By adopting such a configuration, the contact surface of the first contact can always be brought into contact with the same surface more accurately than in the second embodiment, and the resistance value at the first contact can be improved. Can be suppressed.

Embodiment 4 FIG. 6A is a sectional view showing a permanent current switch according to Embodiment 4 of the present invention, and FIG. 6B is a dashed line X in FIG. 6A.
It is the figure which looked at the -Y cross section from the upper part. In the present embodiment,
The guide groove 12 is formed so that the slider 100 directly contacts the superconducting metal member 2.

If the slider 100 is made to directly contact the superconducting metal member 2 as in this embodiment, a high-purity metal member (the movable electrode 1) having a finite resistance value compared to the superconducting metal member 2 is used. Alternatively, a lower contact resistance value can be obtained than in the configuration in which the slider 100 is in contact with the fixed electrode 3). However, since the superconducting metal member is more easily oxidized than the high-purity metal member, the surface state is not stable, and the contact resistance value varies. Therefore, from the viewpoint of obtaining a stable resistance value by suppressing the variation of the contact resistance value, the movable electrode 1 made of a high-purity metal member and the slider 100 are brought into contact with each other as in the third embodiment. Is better.

In the third and fourth embodiments, the guide groove 12 is provided on the movable electrode 1 side, and the slider 100 and the slider base 110 are provided on the fixed electrode 3 side. 12 may be provided on the fixed electrode 3 side, and the slider 100 and the slider base 110 may be provided on the movable electrode 1 side.

Embodiment 5 FIG. 7 is a sectional view showing a permanent current switch according to Embodiment 5 of the present invention. In the present embodiment, as shown in the figure, the slider 100 and the slider base 110 are fixed to the fixed electrode 3 and the inner surface of the space provided in the movable electrode 1 is slid. .

With the above configuration, the slider 100
The contact resistance between the movable electrode 1 and the movable electrode 1 is slightly larger than that in the first embodiment, but the slider 100 and the slider base 1
Since the 10 can be arranged inside the movable electrode 1, the external shape of the permanent current switch can be reduced and the permanent current switch can be made compact.

As shown in FIG. 8, the slider 100 and the slider base 110 are fixed to the movable electrode 1 and the inner surface of the space provided in the fixed electrode 3 is slid. May be.

As shown in FIG. 9, the superconducting metal member 2 is formed up to the sliding portion of the
Is configured to directly contact the superconducting metal member 2,
As described in the fourth embodiment, a lower contact resistance value can be obtained.

The configuration in which the guide grooves 12 are provided in the third and fourth embodiments may be applied to the configuration of the present embodiment.

[0042]

As described above, according to the first aspect of the present invention, there is provided a pair of electrodes which are disposed so as to be able to freely contact and separate from each other, and a permanent contact using a superconducting metal member as a first contact of the pair of electrodes. In the current switch, the pair of electrodes has the second contact made of a high-purity metal member having a resistance lower than the resistance when the superconducting metal member is quenched, so even if the contact by the superconducting metal member is quenched. The effect that operation can be continued is obtained.

According to the second aspect of the present invention, the second contact is a slider that slides on the outer surface of the electrode during opening / closing operation of the electrode and opens after the first contact. The effect of suppressing the variation in the contact resistance value of the first contact and suppressing the occurrence of spark at the first contact is obtained.

According to the third aspect of the present invention, one of the pair of electrodes has a space and the other has a second contact, and the second contact slides on the inner surface of the space when the electrode is opened and closed. Since it is a slider that moves and opens after the first contact,
The effect of suppressing the variation in the contact resistance value of the first contact, suppressing the occurrence of spark at the first contact, and making the permanent current switch compact can be obtained.

According to the fourth aspect of the present invention, since the guide groove is provided on the outer surface of the electrode and the slider slides in the guide groove, variation in the contact resistance value of the first contact is suppressed. The effect is obtained.

According to the fifth aspect of the present invention, since the guide groove is provided on the inner surface of the space and the slider slides in the guide groove, variation in the contact resistance value of the first contact is suppressed. The effect is obtained.

According to the sixth aspect of the present invention, since the surface of the guide groove that contacts the slider is a superconducting metal member, the effect of reducing the contact resistance of the second contact can be obtained.

According to the seventh aspect of the present invention, since the surface of the guide groove which comes into contact with the slider is a high-purity metal member, an effect of suppressing variation in the contact resistance value of the second contact can be obtained. .

[Brief description of the drawings]

FIG. 1 is a sectional view showing a persistent current switch according to Embodiment 1 of the present invention.

FIG. 2 is a diagram showing characteristics of the permanent current switch according to the first embodiment of the present invention.

FIG. 3 is a sectional view showing a permanent current switch according to a second embodiment of the present invention.

FIG. 4 is a sectional view showing another permanent current switch according to Embodiment 2 of the present invention.

FIG. 5 is a sectional view showing a permanent current switch according to a third embodiment of the present invention.

FIG. 6 is a sectional view showing a permanent current switch according to a fourth embodiment of the present invention.

FIG. 7 is a sectional view showing a permanent current switch according to a fifth embodiment of the present invention.

FIG. 8 is a sectional view showing another permanent current switch according to Embodiment 5 of the present invention.

FIG. 9 is a sectional view showing another permanent current switch according to Embodiment 5 of the present invention.

FIG. 10 is a sectional view showing a conventional permanent current switch.

FIG. 11 is a diagram showing characteristics of a conventional permanent current switch.

[Explanation of symbols]

1 movable electrode, 2 superconducting metal member, 3 fixed electrode, 4
Superconducting metal member, 5 movable side metal lid, 6 movable side metal cylinder, 7 bellows, 8 insulating cylinder, 9 fixed side metal cylinder, 1
0, 11 high-purity metal members, 12 guide grooves, 100
Slider, 110 slider base

Claims (7)

[Claims] 1. A permanent current switch comprising a pair of electrodes arranged so as to be able to freely contact and separate from each other and using a superconducting metal member as a first contact of the pair of electrodes, wherein the pair of electrodes are
A permanent current switch comprising a second contact made of a high-purity metal member having a resistance value lower than a resistance value when the superconducting metal member is quenched. 2. The permanent contact according to claim 1, wherein the second contact is a slider that slides on the outer surface of the electrode when the electrode is opened and closed, and opens after a delay from the first contact. Current switch. 3. One of the pair of electrodes has a space on one side and a second contact on the other side, and the second contact slides on the inner surface of the space when the electrode is opened and closed, and the second contact is higher than the first contact. 2. The permanent current switch according to claim 1, wherein the slider is a slider that opens with a delay. 4. The electrode according to claim 2, wherein a guide groove is provided on an outer surface of the electrode, and the slider slides in the guide groove.
A permanent current switch as described. 5. A guide groove is provided on an inner surface of the space, and a slider slides in the guide groove.
A permanent current switch as described. 6. The permanent current switch according to claim 4, wherein the surface of the guide groove that contacts the slider is a superconducting metal member. 7. The permanent current switch according to claim 4, wherein the surface of the guide groove that contacts the slider is a high-purity metal member.