JPH0779015B2 - Vacuum interrupter formation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a method for forming a vacuum interrupter, which is devised so that the surface of an electrode can be formed uniformly.

B. Outline of the Invention The present invention applies a longitudinal magnetic field to the arc of the vacuum interrupter during formation, and adjusts the frequency of the formation current so that the vacuum interrupter is fully opened when the formation current peaks. Uniformly spreads over the entire electrode surface, and the arc spreads evenly over the entire electrode surface, so that uniform formation of the electrode surface can be performed.

C. Conventional technology Vacuum circuit breakers are widely used as circuit breakers that are small, lightweight, highly reliable, and easy to maintain. The main component of the vacuum circuit breaker is a vacuum interrupter.In this vacuum interrupter, a pair of electrodes facing each other are introduced in a vacuum container of about 10 ^-5 Torr, and one of them is brought into contact with and separated from the other. It is designed to open and close circuits.

On the other hand, this vacuum interrupter needs to be in a high vacuum state, and in the manufacturing process thereof, it receives a heat load during brazing and during heating and exhausting. For this reason, the electrode surface may be roughened by a heat load, and the predetermined dielectric strength and dielectric recovery characteristics may not be obtained in the initial stage. Therefore, this type of vacuum interrupter is generally subjected to so-called current formation, in which an arc is generated between the electrodes and the arc cleans the surface of the electrodes.

The earliest chemical conversion method according to the related art is to generate an arc between the electrodes by applying an AC voltage between the electrodes of the vacuum interrupter for chemical conversion in the closed state and opening the electrodes while maintaining this applied state. It is to let.

However, in the above-mentioned chemical conversion method, when the electrodes of the vacuum interrupter are other than the vertical magnetic field type such as the disk electrode, the spiral electrode and the cup electrode, the paper generated by the chemical formation adheres to the inner peripheral surface of the vacuum container and stains it. Therefore, since the number of times of formation and the current value are limited, there is a problem that sufficient formation cannot be performed especially when the diameter of the electrode is large.

As a chemical conversion method capable of solving such a problem, a method has been proposed in which a longitudinal magnetic field is applied by a coil arranged outside a vacuum interrupter for chemical conversion.

FIG. 1 shows a circuit for realizing a chemical conversion method for applying a longitudinal magnetic field, FIG. 4 shows a waveform of a chemical current at that time, and FIG. 5 shows a waveform of a stroke at the time of opening a vacuum interrupter for chemical conversion at that time. Show each.

In FIG. 1, 1 is an AC power supply, 2 is an auxiliary vacuum circuit breaker, 3 is a vacuum interrupter for chemical formation, 4 is a coil for generating a vertical magnetic field,
5 is an AC power supply for the coil 4, D is a diode, R is a resistor, L is a reactor, and C is a capacitor.

When the vacuum interrupter 3 is formed by using such a circuit, the capacitor C is charged with a DC voltage, the auxiliary vacuum circuit breaker 2 and the formation interrupter 3 are closed, and an oscillating current of 50 Hz is generated by the LC circuit. After that, the vacuum interrupter 3 is opened to generate an arc between the electrodes of the vacuum interrupter 3. At this time, the coil 4 causes a longitudinal magnetic field in the same direction as this arc to act on the arm.

In FIG. 5, A is the closed position of the vacuum interrupter in the auxiliary vacuum circuit breaker 2, B is the opening start position of the vacuum interrupter 3, and C is the fully open position of the vacuum interrupter 3.

As is clear by referring to FIG. 4 and FIG. 4 together, the fully open position A of the vacuum interrupter 3 substantially coincides with the zero point of the formation current. This is because, in general, the vacuum interrupter 3 is designed in consideration of extinguishing the arc when the current at the time of interruption becomes zero, and the opening speed by the operating device is also determined accordingly. is there.

D. Problems to be Solved by the Invention By the way, when current formation is performed by applying a longitudinal magnetic field, in the above-mentioned conventional technique, the gap between the electrodes of the vacuum interrupter 3 at the peak of the formation current is short, that is, At the peak of the formation current shown in FIG. 4, as shown in FIG. 5, the electrode is not opened up to about half the fully opened position, so that there is a problem that the arc does not sufficiently diffuse on the electrode surface. This is the same whether the coil is arranged outside or inside the vacuum interrupter, that is, in the case of a vertical magnetic field type vacuum interrupter, but especially when the diameter of the electrode becomes larger than 100 mm The result is that the outer peripheral portion of the is left unformed and remains.

As a countermeasure, 1) increasing the maximum value of the formation current, 2) increasing the number of formations can be considered, but the former not only requires a large facility but also has the problem that the central part of the electrode is damaged. It was found that only the central part of the electrode was formed, and it had no effect.

The present invention has been made in view of the above prior art, and an object thereof is to provide a method for forming a vacuum interrupter capable of forming the surface of the electrode uniformly even if the diameter of the electrode is increased.

E. Means for Solving the Problems The constitution of the present invention which achieves the above-mentioned object is to apply an AC voltage between the electrodes of the vacuum interrupter in the closed state, and to open the electrodes while maintaining this applied state. An arc is generated between the electrodes by the arc, and in the method of forming a vacuum interrupter that cleans the surface of the electrode by this arc, a magnetic field in the same direction as this arc is applied to the arc by a coil, and the formation current The vacuum interrupter is opened by adjusting the frequency of the formation current so that the current value reaches a peak.

F. Action According to the present invention having the above configuration, the formation current also reaches a peak when the vacuum interrupter is fully opened. That is, the arc energy is maximized when the electrode is fully opened, so that the arc is diffused uniformly over the entire surface of the electrode.

G. Examples Hereinafter, the present invention will be described in detail based on examples with reference to the drawings.

In this embodiment, the vacuum interrupter 3 is formed into a current by using the circuit shown in FIG.

The various conditions at this time are as follows.

1) formation circuit voltage: 4kV, current; 31.5 × ▲ √ ▼ 2kA 2) formation vacuum interrupter 3 rated voltage; 84kV (rms) rated current; 31.5kA (rms) gap length; 60 (mm) electrode; diameter 110 (Mm) Spiral Rated opening speed: 3 m / s Under the above conditions, in this embodiment, the frequency of the formation current is adjusted so that the electrode of the vacuum interrupter is fully opened when the current value of the formation current peaks. This frequency adjustment is easily achieved by keeping the capacitance of the capacitor C constant and changing the inductance of the coil L.

The solid line in FIG. 2 shows the waveform of the formation current according to this embodiment, and FIG. 3 shows the stroke waveform when the vacuum interrupter 3 according to this embodiment is opened. In both figures, A is the closing position of the auxiliary vacuum interrupter 2, B is the opening start position of the vacuum interrupter 3, C is the fully open position of the vacuum interrupter 3, and D is the peak of the formation current.

In the present embodiment, the fully open position C of the vacuum interrupter 3 and the peak time D of the formation current match. On the other hand, the waveform of the formation current (50 Hz) in the prior art is shown by the alternate long and short dash line in FIG. 2, and its peak time is indicated by the symbol E in FIG.
The opening position of the vacuum interrupter 3 at
Each is shown in the figure. As shown in FIG. 2, the formation current of this embodiment has a lower frequency (30 Hz) than the formation current in the prior art, and the peak D is delayed with respect to the peak time E.

According to the present embodiment, since the gap between the electrodes becomes maximum at the peak of the formation current having the highest arc energy, the longitudinal magnetic field acts on the entire electrode surface to uniformly diffuse the arc on the entire electrode surface.

FIG. 6 shows the results of examining the withstand voltage characteristics of the vacuum interrupter after the chemical conversion in the present invention and the conventional one in which the longitudinal magnetic field was applied under the same chemical conversion conditions as described above.

FIG. 6 is a graph showing impulse withstand voltage characteristics when current formation is performed by applying a vertical magnetic field. In the figure, the mark ◯ indicates the case of the present invention, and the mark ◎ indicates the average of the withstand voltage values in the conventional case.

As is clear from FIG. 6, it was confirmed that according to the present invention, stable withstand voltage characteristics were obtained from the initial stage.

As is apparent from FIG. 2, when the frequency of the formation current is lowered, its peak value is also lowered, but the peak value of the formation current at the frequency which becomes a peak when the vacuum interrupter 3 is fully opened becomes a predetermined current value. There is no problem if you decide the voltage value. In addition, the frequency of the formation current is 40Hz, considering the stroke waveform when the general vacuum interrupter opens.
It should be selected to about 20Hz.

Further, although the vertical magnetic field is generated by the external coil in the above embodiment, it may be generated by the internal coil, that is, the coil of the vertical magnetic field type vacuum interrupter.

H. Effect of the Invention As specifically described with the above embodiments, according to the present invention, since the frequency of the formation current is adjusted so that the current value of the formation current becomes a peak when the vacuum interrupter is fully opened,
At the peak of the formation current with the highest arc energy, the gap between the electrodes is maximum, so that the longitudinal magnetic field acts uniformly on the entire electrode surface. As a result, the electrode is uniformly formed even if its diameter is increased.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a chemical formation circuit, FIG. 2 is a waveform diagram showing the waveform of the chemical formation current, and FIG. 3 is a stroke waveform when the vacuum interrupter for chemical formation according to this embodiment is opened. Waveform diagram, FIG. 4 is a waveform diagram showing the waveform of the formation current, FIG. 5 is a waveform diagram showing the stroke waveform when the vacuum interrupter for formation according to the prior art is opened, and FIG. 6 is a longitudinal magnetic field during formation. It is a graph which shows the impulse withstand voltage characteristic of the vacuum interrupter after the chemical conversion in this invention added and the conventional. In the drawing, 1 and 5 are AC power supplies, 3 is a vacuum interrupter, and 4 is a coil.

Claims (1)

[Claims] 1. An AC voltage is applied between electrodes of a vacuum interrupter in a closed state, and the electrodes are opened while the application state is maintained to generate an arc between the electrodes, and the arc cleans the electrode surface. In the vacuum interrupter formation method described above, a magnetic field in the same direction as the arc is applied to the arc by a coil, and the frequency of the formation current is adjusted so that the current value of the formation current reaches a peak when the vacuum interrupter is fully opened. A method for forming a vacuum interrupter, which comprises opening the electrodes.