JPH06196049A - Vacuum valve - Google Patents

Abstract

PURPOSE:To obtain a vacuum valve wherein dielectric breakdown is prevented from the point end part of a mounting member for mounting an arc shield, provided so as to surround electrodes, to an insulating cylinder to improve reliability. CONSTITUTION:An arc shield 2 is provided so as to surround a fixed electrode 11 and a movable electrode 13, and this arc shield 2 is mounted to an insulating cylinder 1 by a mounting metal fixture 3. On the other hand, in order to avoid electric field concentration in a point end part of the mounting metal fixture 3, an electric field intensity relaxing means is provided in this point end part.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to vacuum valves.

[0002]

2. Description of the Related Art Generally, a vacuum valve has at least a pair of fixed and movable electrodes which can be brought into contact with and separated from each other in a vacuum container formed by hermetically sealing an insulating cylinder. When the current is cut off by the pair of electrodes, metal vapor is generated from the electrode surface due to the heat generated by the arc, and if this metal vapor scatters and adheres to the inner surface of the insulating cylinder, the insulation characteristics as a vacuum valve deteriorate and the cutoff characteristics Adversely affect. For this reason, a cylindrical arc shield made of metal is placed around the electrode,
The metal vapor is prevented from adhering to the inner surface of the insulating container. This arc shield is supported on the inner surface of the insulating cylinder by a mounting bracket.

FIG. 5 shows a structure of attaching an arc shield in a conventional vacuum valve. A convex portion 1a is provided on the inner surface of the insulating cylinder 1, and a step portion 2a that engages with the convex portion 1a is provided on the arc shield 2. The step portion 2a and the flange portion 3a of the mounting member 3 fixed to the arc shield 2 sandwich the convex portion 1a, and the end portion of the arc shield 2 and the cylindrical portion 3b of the mounting member 3 are aligned with each other. . By welding the end face A, the arc shield 2 is supported and fixed at a position insulated from the electrodes.

[0004]

However, in the ark shield mounting structure of the conventional vacuum valve, due to the electric field concentration at the tip 3c of the flange 3a of the mounting bracket 3, the flange 3a of the mounting bracket 3 is formed. The through hole 4 may be formed in the root portion 1b of the convex portion of the insulating cylinder 1 adjacent to the tip portion 3c due to dielectric breakdown due to discharge. In particular, in order to improve the withstand voltage performance between electrodes, a standard (for example, JE
C-2300), the through-hole 4 is easily generated in the case where an AC voltage of several times the commercial frequency withstand voltage is applied to cause discharge between the electrodes, that is, so-called voltage conditioning is performed. When such a through hole 4 is formed, the vacuum inside the vacuum container cannot be maintained, and the performance of the vacuum valve is impaired. SUMMARY OF THE INVENTION It is an object of the present invention to provide a vacuum valve having an improved arc shield support structure and improved reliability.

[0005]

In order to achieve the above object, the present invention provides a pair of electrodes which can be contacted and separated from each other in a vacuum container formed by hermetically sealing the ends of an insulating cylinder. In the vacuum valve having an arc shield provided so as to surround the pair of electrodes, the electric field strength relaxation means is formed at the tip of the attachment means for attaching the arc shield to the insulating cylinder. It is possible to suppress dielectric breakdown starting from.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. The same components as those of the conventional vacuum valve are designated by the same reference numerals and the description thereof will be omitted.

FIG. 1 is a sectional view of the vacuum valve of the present invention. In the figure, reference numeral 1 is an insulating cylinder, and both ends thereof are hermetically closed by metallic end plates 7 and 8 via seal rings 5 and 6 to form a vacuum container 9. The inside of the vacuum container 9 is maintained at a high vacuum of 10 ⁻³ Pa or less.

Reference numeral 10 denotes a fixed electrode rod, which penetrates the end plate 7 in an airtight manner and is fixed to the end plate 7, and a fixed electrode 11 is fixed to the tip thereof. 12 is a movable electrode rod, and the other end plate 8
The movable electrode 13 is fixed to the tip of the movable electrode 13 so as to face the fixed electrode 11. This pair of fixed and movable electrodes
The current is cut off by 11 and 13. Reference numeral 14 denotes a metal bellows, which is attached between the movable electrode rod 12 and the end plate 8 so as to maintain airtightness between them and allow the movable electrode rod 12 to function.

In such a vacuum valve, the metallic arc shield 2 is supported and fixed to the inner surface of the insulating cylinder 1 by a mounting member 3. The structure of the mounting portion of the arc shield 2 will be described in detail with reference to FIG. A convex portion 1a is formed on the inner surface of the insulating cylinder 1, and a step portion 2a is formed on the arc shield 2 so as to engage with the convex portion 1a. Then, the convex portion 1a is sandwiched between the step portion 2a of the arc shield 2 and the flange portion 3a of the mounting bracket 3, and the end portion of the arc shield 2 and the cylindrical portion 3b of the mounting bracket 3 are sandwiched.
The end face A is welded and the end face A is welded to fix the arc shield 2 and to support and fix it at a position insulated from the movable electrodes 11 and 13. Here, the tip portion 3 facing the non-convex portion of the inner surface of the insulating cylinder of the flange portion 3a of the mounting bracket 3
The radius of curvature of c is processed so as to be equal to or greater than the plate thickness of the arc shield.

In the vacuum valve thus constructed, the radius of curvature of the tip portion 3c of the flange 3a of the mounting member 3 facing the non-convex portion of the inner surface of the insulating cylinder is set to be equal to or larger than the plate thickness of the arc shield 2. By doing so, the electric field concentration at the tip portion 3c of the collar portion 3a is alleviated, and the dielectric breakdown of the insulating cylinder 1 that originates at the tip portion 3c is suppressed. Therefore, no through hole is formed in the insulating cylinder 1 due to application of a high voltage during manufacturing or testing of the vacuum valve, and performance deterioration of the vacuum valve can be prevented.

Table 1 shows a comparison between the probability of occurrence of through holes in the conventional example and the probability of occurrence of through holes in this example (T indicates the plate thickness of the arc shield 2). The survey results in Table 1 are for an average thickness of the insulating cylinder of 5.5 mm and an AC voltage applied between both electrodes of 130 kV-15 seconds x 3 times (standard condition). The applied voltage was applied to a range larger than the voltage condition at the time of actual manufacturing, but this is because the probability of penetration breakdown is very small under the voltage condition at the time of actual manufacturing. As described above, if the radius of curvature of the tip portion 3c of the collar portion 3a is equal to or larger than the plate thickness of the arc shield, it may be considered that the penetration failure does not practically occur.

[0012]

[Table 1]

The present invention is not limited to this embodiment, and as shown in FIG. 3, the tip portion 3c of the collar portion 3a is rounded so that the radius of curvature becomes equal to or larger than the plate thickness of the arc shield 2. Alternatively, as shown in FIG. 4, a ring having a radius equal to or larger than the plate thickness of the arc shield 2 may be fixed to the tip of the flange 3c.

[0014]

As described above, according to the present invention, a pair of electrodes which can be contacted and separated from each other are arranged in a vacuum container formed by hermetically sealing the ends of an insulating cylinder, and the pair of electrodes are surrounded. In a vacuum valve with an arc shield provided,
Since the electric field strength relaxation means is formed at the tip of the attachment means for attaching the shield to the insulating cylinder, it is possible to suppress the dielectric breakdown from the tip of the attachment means and obtain a vacuum valve with improved reliability. .

[Brief description of drawings]

FIG. 1 is a sectional view of a vacuum valve showing an embodiment of the present invention.

FIG. 2 is a partially enlarged sectional view of FIG.

FIG. 3 is a partially enlarged sectional view of a vacuum valve showing another embodiment of the present invention.

FIG. 4 is a partially enlarged sectional view of a vacuum valve showing another embodiment of the present invention.

FIG. 5 is a partially enlarged sectional view of a conventional vacuum valve.

[Explanation of symbols]

1 ... Insulation cylinder, 2 ... Arc shield, 3 ... Mounting bracket, 3a
... Collar, 3c ... Tip

Claims (3)

[Claims] 1. A pair of electrodes, which can be freely contacted and separated, are provided in a vacuum container formed by hermetically sealing the ends of an insulating cylinder, and an arc shield is provided so as to surround the pair of electrodes. In the vacuum valve, the electric field strength reducing means is formed at the tip of the mounting means for mounting the arc shield on the insulating cylinder. 2. The vacuum valve according to claim 1, wherein, as the electric field strength reducing means, a radius of curvature of a tip portion of the attaching means is equal to or larger than a thickness of the arc shield. 3. The vacuum valve according to claim 1, wherein a ring having a radius equal to or larger than a thickness of the arc shield is provided at a tip end portion of the attaching means as the electric field strength reducing means.