JPS596587Y2 - vacuum valve - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a vacuum valve, and particularly to a vacuum valve with improved intermediate shield and end shield.

The shield of a vacuum breaker plays a major role in preventing metal vapor generated between the electrodes from adhering to the inner surface of the insulating container when the current is interrupted.

However, since the discharge causes creeping discharge from the shield through the insulating container, improvement in the unit voltage of the vacuum bulb is hindered.

Figure 1 shows the structure of a conventional circuit breaker.

1 is a contact point, and 2 is an electrode, at which the current is cut off.

Reference numeral 3 denotes a fixed current-carrying shaft that passes through the fixed side cover plate 4 and is bonded to one side of the electrode 2.

Reference numeral 5 denotes a movable current-carrying shaft, which is connected to the movable side cover plate 7 via a bellows 6, and whose tip end is connected to the other side of the electrode 2.

8 is an intermediate shield that prevents the arc generated between the contacts 1 from directly contacting the inner surface of the insulating container 9 when the current is cut off.

This intermediate shield 8 is electrically insulated from both contacts by supporting it in the middle using two insulating containers 9.

Reference numeral 10 denotes an end shield, which is provided to relieve the electric field at the sealed portion of the insulating container 9.

As shown in FIG. 1, an intermediate shield 8 and an end shield 1
Since the insulating container 9 is present near the point 0, the discharge progresses from the shield via the insulating container 9.

For this reason, it is known that the breakdown voltage is low. This is the second
As shown in Figure a, when a positive voltage is applied to the intermediate shield 8, electrons emitted from the cathode end shield 10 collide with the insulating container 9 and emit secondary electrons.

The collision energy and secondary electron emission efficiency δE at this time are expressed as
As shown in the figure.

Electrons emitted from the end shield 10 according to this δE curve emit secondary electrons.

This secondary electron avalanche multiplies electrons due to the electric field intensity distribution on the inner surface of the insulating container as shown in FIG. 2b, and finally leads to dielectric breakdown.

Since the electric field strength on the inner surface of the insulating container is thus high, the breakdown voltage is low.

In recent years, the unit voltage of vacuum valves has been increased to a higher voltage, but for the above-mentioned reasons, increasing the voltage has become a big problem.

This proposal was made to eliminate the above-mentioned drawbacks, and by setting the inclination angle of the opposing sides of the intermediate and end shields to 10 to 25 degrees with respect to the surface of the insulating container, the withstand voltage can be improved. The purpose is to provide a vacuum valve with excellent performance.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 shows the overall structure of the vacuum valve of the present invention.

1 is a contact point, and 2 is an electrode, at which the current is cut off.

Reference numeral 3 denotes a fixed current-carrying shaft that passes through the fixed side cover plate 4 and is bonded to one side of the electrode 2.

Reference numeral 5 denotes a movable current-carrying shaft, which is connected to the movable side cover plate 7 via a bellows 6, and whose tip end is connected to the other side of the electrode 2.

8 is an intermediate shield that prevents the arc generated between the contacts 1 from directly contacting the inner surface of the insulating container 9 when the current is cut off.

This intermediate shield 8 is electrically insulated from both contacts by supporting it in the middle using two insulating containers 9.

Reference numeral 10 denotes an end shield, which is provided to relieve the electric field at the sealed portion of the insulating container 9.

The difference from the conventional example is that the opposing sides of the intermediate shield 8 and the end shield 10 have an inclination angle of 10 to 25 degrees with respect to the surface of the insulating container.

That is, in the intermediate shield 8, the supporting portion 8a extends in parallel with the insulating container 9, and the intermediate portion 8b extending continuously with the supporting portion 8a is separated from the inner surface of the insulating container 9 by 10 to 2.
It extends with an inclination of 5°.

The end of this intermediate portion 8b is rounded into a ring shape.

Also, in the end shield 10, the parallel parts 10a to 10
It has an inclined portion 10b of ~25°, and the end of the inclined portion 10b is rounded.

Next, the operation of the present invention constructed as above will be explained.

FIG. 5a shows details of the intermediate shield 8 and end shield 10 of the present invention, and FIG. 5b shows the electric field intensity distribution on the inner surface of the insulating container 9.

A shows the electric field strength distribution due to the conventional shield shape, and B shows the electric field strength distribution due to the proposed shield shape.

In this way, by providing the intermediate shield 8 and the end shield 10 with the inclination angle φ, the electric field intensity distribution is made more uniform than in the conventional example.

Conventionally, the locations where the electric field strength on the inner surface of the insulating container 9 is maximum are a1 and bl, but according to the present invention, the locations are a2 + b2.

As a result, as can be seen from FIG. 5, the leakage distance on the inner surface of the insulating container 9 becomes longer than in the conventional case.

By making the electric field strength distribution uniform, the maximum electric field strength E
max can be lowered.

The relationship between the inclination angle φ of the intermediate shield 8 and the end shield with respect to the surface of the insulating container 9 and the maximum electric field strength Emax is expressed as
As shown in the figure.

Here, d is the distance between the insulating container 9 and each shield where they face each other in parallel.

This distance d for an actual vacuum valve is constrained for the following reasons.

As shown in FIG. 4, the distance r1 between the current-carrying shaft 3 and the intermediate shield 8 must be larger than the diameter of the electrode 2 in order to maintain the insulation distance between the current-carrying shaft 3 and the intermediate shield 8 and to facilitate assembly. Must be.

Therefore, the distance d actually used is d1 to d3.

The relationship between d1, d2, and d3 in FIG. 6 is d. <d2
<It is d3.

The relationship between the maximum electric field strength Emax and the inclination angle φ is a curve with extreme values.

Since the conventional inclination angle is O°, the maximum electric field strength is d3
Emax, even when .

On the other hand, if the inclination angle is 10 to 25 degrees, d1 to d3
Even if an arbitrary value is selected, it can be made to be at least EmaX2 or less, and the maximum electric field strength can be significantly lowered than in the past.

In this way, the electric field strength on the inner surface of the insulating container is made uniform, the maximum electric field strength is lowered, and the leakage distance is increased, so that the withstand voltage performance is improved.

Therefore, a vacuum valve suitable for high voltage applications can be provided.

As explained above, according to the present invention, by providing the intermediate shield and the end shield with an inclination angle of 10 to 25 degrees,
It is possible to improve the withstand voltage between the intermediate shield and the end shield, improve the withstand voltage performance as a vacuum valve, and provide a vacuum valve suitable for high voltage applications.

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional view showing a conventional vacuum valve, Fig. 2a is a detailed explanatory diagram between the intermediate shield and the end shield, Fig. 2b is a diagram of the electric field intensity distribution on the inner surface of the insulating container, and Fig. 3 is a diagram showing the relationship between secondary electron emission efficiency and electron collision energy,
Fig. 4 is a longitudinal sectional view showing an embodiment of the vacuum valve of the present invention, Fig. 5a is a line diagram showing details between the intermediate shield and the end shield of the invention, and Fig. 5b is the insulation according to the invention. FIG. 6, which is an electric field strength distribution diagram on the inner surface of the container, is a curve diagram showing the relationship between the shield inclination angle and the maximum electric field strength. 1... Contact, 2... Electrode, 3...
...Fixed current-carrying shaft, 4...Fixed side cover plate, 5...
...Fixed current-carrying shaft, 6...Bellows, 7...
...Movable side cover plate, 8...Middle shield, 9.
...Insulating container, 10... End shield.

Claims (1)

[Scope of utility model registration request] A pair of removable electrodes is arranged in a vacuum container consisting of an insulating container and a lid plate that closes the insulating container, and at least one of the pair of electrodes is sealed to the lid plate via a bellows, In the vacuum valve, in which an intermediate shield surrounding an electrode is provided in the insulating container, and an end shield is provided on the lid plate, the end shield and the intermediate shield are placed facing each other with respect to the surface of the insulating container. A vacuum valve characterized in that the end portions of the vacuum valve are arranged so as to be spaced apart at an inclination angle of 10 to 25 degrees.