JPH06139886A - Vacuum valve - Google Patents

Abstract

PURPOSE:To provide a vacuum valve increasing the critical current value at an electrode to form an arc spot when the current is cut off and maintaining the excellent cutoff performance. CONSTITUTION:Contact pieces 7 at the middle section and outer periphery of a contact 5 are formed into a protruded shape toward an electrode 4 side on the contact 5 of the electrode 4 of a vacuum valve. The material of a recessed contact piece 8 at the middle section has the melting point, heat conductivity, specific heat, and density larger than those of the material of the contact piece 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum valve, and more particularly to an electrode structure.

[0002]

2. Description of the Related Art As an electrode structure of a vacuum valve for improving a breaking current, there is a vertical magnetic field type electrode for applying a magnetic field parallel to a vacuum arc. Although there are some vertical magnetic field type structures, the structure shown in FIG. 3 will be described here.

The fixed and movable electrodes of the vacuum valve shown in FIG. 3 are arranged coaxially, and the movable current-carrying shaft is connected to an operation mechanism portion (not shown) via a bellows. Structurally,
The movable and fixed electrodes are the same, and the structure is symmetrical with respect to the center line between the electrodes. Hereinafter, one of the electrodes will be described.

A current flowing through the current-carrying shaft 1 flows in a radial direction through the arm portion of the coil electrode 2 and further flows in a current passage provided in the circumferential direction of the electrode to generate a magnetic field in the axial direction. Furthermore, this current is
It flows to the electrode 4 and the contact 5.

On the other hand, when the current is cut off, an arc is ignited between the electrodes 4, the movable and fixed electrodes are electrically connected, and the current flows toward the opposing electrodes in the reverse order described above. .

By the way, it is well known that the arc can be uniformly spread over the entire electrode surface by applying a magnetic field parallel to the arc. Therefore, with such an electrode structure, it is possible to suppress the formation of an anode spot (which has an adverse effect upon interruption) up to a large current region. Also, part of the anode electrode is overheated,
Even when the electric current is cut off, the surface temperature of the anode electrode is considerably high, so that the evaporation of the electrode material becomes active and the interruption of the electric current is prevented.

[0007]

However, in the conventional vacuum valve electrode structure, the critical current value at which the anode spot is formed is uniquely determined by the contact material used and the electrode diameter. In order to increase this critical current value, it is necessary to have an electrode structure that optimizes the longitudinal magnetic field strength and distribution, and its adjustment is extremely difficult. Further, it is hard to say that the critical current value can be made sufficiently large even with such adjustment.

The object of the present invention is to increase the critical current value at which the anode spot is formed even if the electrode diameter is the same,
It is to provide a vacuum valve that can maintain excellent shutoff performance.

[0009]

In order to achieve the above object, according to the present invention, a pair of electrodes are provided in a vacuum container so that they can come into contact with and separate from each other, and a magnetic field parallel to the axial direction of the electrodes is applied to the pair of electrodes. In a vacuum valve provided with an electrode for generating, a central portion and an outer peripheral portion of contact points of a pair of electrodes are provided in a convex shape on the counter electrode side with respect to an intermediate portion, and an intermediate portion of the contact point has a melting point higher than the central portion and the outer peripheral portion, Since the material having large thermal conductivity, specific heat and density is used, the critical current value for forming the anode spot can be increased.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. The same parts as those of the conventional one are designated by the same reference numerals and the description thereof will be omitted.

FIG. 1 is a sectional view of an electrode of a vacuum valve of the present invention. In the same figure, the contactor 7 is formed so that the central portion and the outer peripheral portion of the contact point of the electrode 4 project toward the other facing electrode
The intermediate portion between them becomes concave as seen from the contactor 7, as shown by the contactor 8.

More specifically, in order to make the surface of the contact 8 (made of, for example, molybdenum or tungsten) having a high melting point and a large density, specific heat and thermal conductivity lower than the surface of the contact 7 by several mm. A ring-shaped counterbore is provided in the intermediate region between the electrode center and the outer periphery. The radial length of the ring-shaped region may be about 10 to 20% of the electrode radius.

On the other hand, in the central portion and the outer peripheral portion on the electrode 4,
Contact 7 for breaking high voltage and large current (eg Cu-Cr
(Comprising) is brazed to the electrode 4. Also, the electrode 4
The melting point is high on the ring-shaped counterbore part of
The contactor B having a large thermal conductivity is brazed. When the current is cut off, either the movable electrode or the fixed electrode may be on the anode side, so both electrodes have such an electrode structure.

The present inventor has found such an electrode structure based on the following knowledge. That is,
The general theory to explain the formation of the anode spot is that in a large current region, the current distribution near the anode contracts, causing excessive input energy (energy due to electrons, ions, etc. reaching the anode electrode) to a part of the anode. )
It is considered that the electrode surface reaches the melting point and the evaporation of the material from the electrode becomes active. Therefore, in order to suppress the formation of the anode spot up to a large current, it is necessary to suppress the concentration of the input energy or prevent the surface from reaching the melting point even when the input energy is incident. The longitudinal magnetic field is effective for the former but not effective for the latter, so it is necessary to improve it like the latter.
FIG. 2 is a characteristic diagram showing a temperature distribution of an electrode to which a vertical magnetic field is applied.

According to the figure, it can be seen that the heat input becomes maximum (maximum temperature) at the intermediate portion between the electrode central portion and the outer peripheral portion. Therefore, as shown in FIG. 1, by embedding the contact 8 having a high melting point and a high density, specific heat, and high thermal conductivity in a region having the largest heat input, even if the heat input is large, Reaching the melting point during the arc period is considerably suppressed compared to the past. Therefore, the critical current value at which the anode spot is formed is significantly improved as compared with the case where only the contact A is used.

One electrode is on the cathode side,
Since the surface of the contactor 8 is lower than the surface of the contactor 7 by several mm, the cathode spot is ignited on the contactor 8 and becomes difficult. Therefore, most of the arc plasma formed between the electrodes is evaporated from the contactor A, and the influence of the contactor 8 can be suppressed as much as possible. Therefore, it is considered that the energy input to the anode electrode will be almost the same as the conventional one.

[0017]

As described above, according to the present invention, the contact points of the pair of electrodes in the vacuum container are provided so that the central portion and the outer peripheral portion thereof are convex toward the opposing electrode side rather than the intermediate portion, and the intermediate portion is formed. Is a material whose melting point, thermal conductivity, specific heat and density are higher than those of the central and outer parts, so the critical current value at which an arc spot is formed on the electrode can be increased regardless of the contact material used and the electrode diameter. It is possible to obtain a vacuum valve that can maintain the shutoff performance.

[Brief description of drawings]

FIG. 1 is a sectional view of an electrode portion of a vacuum valve of the present invention.

FIG. 2 is a diagram showing a temperature distribution of electrodes of a vacuum valve having a general longitudinal magnetic field electrode.

FIG. 3 is a sectional view of an electrode portion of a conventional vacuum valve.

[Explanation of symbols]

 4 ... Electrode, 5 ... Contact, 7, 8 ... Contact

Claims (1)

[Claims] 1. A vacuum valve in which a pair of electrodes are provided in a vacuum container so that they can come into contact with and separate from each other, and the pair of electrodes has an electrode for generating a magnetic field parallel to the axial direction of the electrodes. The central portion and outer peripheral portion of the contact point are provided in a convex shape on the counter electrode side with respect to the intermediate portion, and the intermediate portion of the contact is made of a material having a higher melting point, thermal conductivity, specific heat, and density than the central portion and outer peripheral portion. Vacuum valve characterized by.