JPS648411B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a vacuum switch, and more specifically, a vacuum switch comprising a fixed electrode and a movable electrode that are housed in a vacuum container and that move toward and away from each other. It is related to.

[Conventional technology]

Conventionally, there has been a vacuum switch of this type as shown in FIG. In the figure, a fixed electrode 2 is fixed and housed on one side of a cylindrical vacuum container 1.
A movable electrode 3 that moves linearly in opposition to the fixed electrode 2 is connected and supported to the vacuum vessel 1 by a bellows 4. The bellows cover 5 is used together with the arc shield covers 6 and 7 to protect the inner wall surface of the vacuum vessel 1 from arc plasma generated between the electrodes. The side wall 1a of the vacuum container 1 is made of an insulating material such as glass or ceramic. 8a, 8b
is the end plate of the conductor.

Here, the arc plasma is generated when the gas remaining in the vacuum container 1 becomes ionized gas and the electrodes are opened.

With the above configuration, normally the fixed electrode 2 and the movable electrode 3 are in contact and a current flows between them, but if an accident occurs in the circuit connected to this vacuum switch, the current must be cut off immediately. When the need arises, when the movable electrode 3 is moved in the direction of arrow A to open the circuit, arc plasma P is generated between the electrodes 2 and 3 at the time of opening. If the amount of arc plasma generated at this time is small, the current will be cut off when the voltage applied between the electrodes 2 and 3 becomes very low, and the circuit will be completely opened.

Here, we will discuss the arc plasma instability that occurs between the electrodes, which is also described in Kampen Felderhoff's "Plasma Physics", Kinokuniya Shoten (1973), pages 93-94.

Since current flows through the arc plasma, sausage-shaped and kink-shaped arc plasma instabilities occur. These problems were problems in the early days of plasma fusion research.
This is the most dangerous type of instability. This naturally occurs in the arc plasma generated between the electrodes, thereby increasing the energy injected into the arc plasma from the external circuit. As a result, after the arc plasma crashes, it strongly interacts with the electrode surface and turns the electrode material into plasma. This is undesirable for current interruption. This is because arc plasma is a current carrier, and if there is too much of it, the arc plasma will not disappear immediately when the current becomes zero, and when the voltage is applied between the electrodes again, the current will start flowing again. . Therefore, in order to improve the interrupting performance, it is necessary not to generate much arc plasma, and the method is to suppress the energy injected into the arc plasma. In other words, the essence is to stabilize arc plasma instability.

[Problem to be solved by the invention]

Conventional vacuum switches have the above configuration, and a large amount of energy is input into the arc plasma generated between the electrodes. This is because the arc plasma is unstable and becomes dynamically active, which requires energy. Therefore, energy is injected into the arc plasma from the outside, and the voltage applied between the electrodes increases. Therefore, damage to the electrodes due to arc plasma increases and durability decreases.

This invention was made in order to solve the above-mentioned problem, and its purpose is to obtain a vacuum switch having a long-life electrode.

[Means to solve the problem]

The vacuum switch according to the present invention has a cylindrical vacuum vessel with a side wall made of an insulating material, and has a small diameter part as an arc plasma generation area, and a cylindrical stabilizing conductor wall is attached in contact with the outer peripheral surface of this small diameter part. ing.

[Effect]

In this invention, since there are conductor walls on both sides of the kink-type arc plasma, eddy currents are induced in the conductor wall because the arc plasma approaches the conductor wall in the part of the arc plasma that protrudes toward the conductor side wall. , the magnetic pressure increases.

On the other hand, on the opposite side of the area where the arc plasma protrudes, the magnetic pressure decreases. Therefore, the arc plasma is pushed back toward the central axis due to the presence of the conductor wall.

〔Example〕

Here, prior to explaining the embodiments, stabilization of arc plasma will be described.

In order to stabilize the plasma instability described above, the following two methods are known in the field of plasma physics.

(i) Apply a vertical magnetic field.

(ii) Install conductor walls.

Regarding (i), there are many reports in the field of nuclear fusion research that plasma instability is experimentally stabilized.
Therefore, although not described here, it is known from theoretical analysis that the effect is stabilized by the pressure of the applied vertical magnetic field and the tension in the direction of the magnetic field lines.

Regarding (ii), we will explain Kink-type plasma instability below. When there are conductor walls (shells) on both sides of a kink-type plasma, in other words, there are conductor walls (shells) on both sides of the plasma, eddy currents are induced in the conductor wall because the plasma approaches the conductor wall in the part of the plasma that protrudes toward the conductor wall. , the magnetic pressure increases. On the other hand, on the opposite side from which the plasma protrudes, the magnetic pressure decreases. Therefore, the plasma is pushed back toward the central axis by the presence of the conductor wall. This is a stabilization of plasma instability. That is, if the arc plasma is confined in the center between the electrodes without making it unstable, the energy injected into the arc plasma is reduced, the arc plasma is easily extinguished at the current zero point, and current interruption is completed. The principle of this is different from air shielding and those in which the electrode rotates to open and close. This is the first reason why the conductor wall is provided.The conductor wall is made of a slightly thick material with high conductivity so that eddy currents are easily induced.

This invention is based on the above-mentioned plasma instability stabilization theory and applies it to a vacuum switch.According to theoretical calculations, the above-mentioned shell (conductor wall) effect is caused by the distance between the shell and the arc plasma. Focusing on the fact that the shorter the distance is, the more effective the method is, the arc plasma generation site and conductor wall of the vacuum vessel are made to have small diameters.

Next, an embodiment of the present invention will be described with reference to FIGS. 1 and 2. In FIG. 1, a portion of the cylindrical vacuum vessel 1 corresponding to the position where arc plasma P is generated is defined as a small diameter portion 1b, and a shell, that is, a cylindrical stabilizing conductor wall 9 is in contact with the outer peripheral surface of this portion. It is arranged. This stabilizing conductor wall 9
As shown in the figure, shell members 9a and 9b, which are divided into two on the axial plane, are disposed in the small diameter portion 1b of the vacuum vessel 1 and assembled. Other parts are the same as in FIG. 3.

With the above configuration, the basic operating principle as a vacuum switch is the same as that of the conventional one, but since the stabilizing conductor wall 9 is disposed close to the arc plasma P, the stabilizing conductor wall 9 side In the protruding kink-type arc plasma portion, since the arc plasma approaches the conductor wall 9, an eddy current is induced in the conductor wall 9, and the magnetic pressure increases. On the other hand, the magnetic pressure decreases at a location opposite to the location where the arc plasma protrudes. Therefore, the arc plasma is pushed back toward the central axis due to the presence of the stabilizing conductor wall 9, and the arc plasma is stabilized. This lowers the voltage between electrodes 2 and 3.

Note that the stabilizing conductor wall 9 is not limited to being divided into two, but may be divided into more than two parts, and the same effect can be obtained.

〔Effect of the invention〕

As is clear from the above explanation, this invention
The arc plasma generation area of the vacuum vessel is a small diameter part, and since the stabilizing conductor wall is provided in this small diameter part, the distance between the arc plasma and the stabilizing conductor wall becomes short, promoting stabilization of the arc plasma. As a result, the amount or energy of arc plasma generated is reduced, which in turn suppresses wear and tear on the electrodes and improves durability.

[Brief explanation of drawings]

Fig. 1 is a longitudinal cross-sectional view of one embodiment of the present invention;
This figure is also an exploded perspective view of the main parts, and FIG. 3 is a longitudinal cross-sectional view of a conventional vacuum switch. DESCRIPTION OF SYMBOLS 1... Vacuum vessel, 1a... Side wall, 1b... Small diameter part, 2... Fixed electrode, 3... Movable electrode, 9... Stabilizing conductor wall, 9a, 9b... Shell member. In addition,
In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A pair of electrodes that open and close by linear relative movement; and a portion having at least a side wall made of an insulator, accommodating the pair of electrodes, and corresponding to the position of arc plasma generated when the electrodes are opened. a cylindrical vacuum vessel with a small diameter portion; a cylindrical stabilizing conductor wall disposed in contact with the outer peripheral surface of the small diameter portion for confining the arc plasma toward the central axis side of the small diameter portion; A vacuum switch is provided. 2. The vacuum switch according to claim 1, wherein the stabilizing conductor wall is a combination of shell members divided into a plurality of parts parallel to the cylindrical axis.