JPS593831A - Vacuum breaker - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a vacuum breaker, and particularly to a vertical magnetic field type vacuum breaker with an improved electrode configuration.

[Background technology and its problems]

Vacuum pulp, which generally forms the main part of a vacuum breaker, is produced by installing a pair of electrodes that can be moved in and out of the vacuum container, which is a nearly cylindrical container made of an insulating material such as ceramic, with both ends closed with end plates. It is configured. As shown in FIG. 1, which is a plan view of one electrode, the electrode part has a so-called spiral electrode structure, which has a contact point 1 in the center and an electrode 2 with a spiral groove around the periphery. It has been adopted. This type of spiral electrode structure was adopted to drive the arc at the time of interruption by a rotating magnetic force in order to improve the breaking performance of large current interruptions.As is well known, the arc generated between the contacts is driven by magnetic force. The arc is transferred to a spiral electrode, and the transferred arc is rotated around the electrode by the rotating magnetic force of the spiral groove, thereby preventing local overheating of the electrode, reducing residual metal vapor at the zero current point, and increasing the breaking performance. There used to be. In order to increase the breaking performance with such an electrode structure, it is essential to transfer the arc generated between the contacts to the electrode, and to do this, it is necessary to use materials with a small difference in arc voltage for contact 1 and electrode 2. There is a need to. For this reason, coupled with the fact that copper is usually used as an electrode material because of its high conductivity and excellent cut-off properties, C has been selected as a contact material.

CI type materials such as Cu-B1 type or C1I-T type alloys are preferably used, which have B1 and Te as main components and B1 and Te are added as adhesion prevention ingredients.

However, one problem has arisen in the use of the above-mentioned Cu-based contact materials due to the recent expansion of applications for vacuum circuit breakers. That is, the above Cu-based contact material was added as a welding prevention component due to the high temperature arc during current switching.

There is a problem that B1 and To are selectively evaporated, and as a result, the current cutoff level becomes high during use, and there is a problem that switching surges are likely to occur. The drawback of this Cu-based contact material is that it has a high current cutting level.
Vacuum circuit breakers were generally used in systems with low surge impedance, so there were few problems. However, in recent years, systems have become more complex, and the number of cases in which vacuum circuit breakers are used to switch inductive loads such as large-capacity motors has increased, and it has become necessary to solve the problem of switching surges depending on the applied load. ing. In such cases, it is possible to suppress harmful surges by adding a surge absorber outside the vacuum breaker. On the other hand, Ag-WC-based sintered alloys are known as low-surge contact materials. This contact material has excellent low surge characteristics and is often used in vacuum contactors that do not require much breaking performance.

However, this material L1 and cutoff characteristics are considerably inferior to those of the above-mentioned CU-based contact materials, so there is a problem with its use in vacuum valves for circuit breakers that require large current cutoff. The reason why the breaking characteristics of Ag-WC type contact materials are inferior is that the arc voltage is lower than Cu, and the arc generated between the contacts cannot be transferred to the single pole. Tota, another reason is Ag-W.
Another problem with C-based contact materials is that new phenomena are different from those of conventional materials, making it impossible to apply new theories.

In other words, as is well known, the breaking flux of a vacuum breaker is:
This method utilizes the diffusion effect in vacuum of metal vapor generated by the arc when the current is cut off, and a large amount of metal vapor is generated from the electrode during the arc generation period. As soon as the metal vapor is generated, it diffuses into the surrounding vacuum space, adheres to the low-temperature parts of the arc shield and electrodes, and condenses, but the vapor pressure is relatively high in the area where the arc occurs. When the current is at zero, the energy supplied to the arc is zero, but the breaking performance of a vacuum breaker is greatly influenced by the metal vapor remaining at this zero current. After the current zero point, the remaining metal vapor diffuses at a rapid rate and the metal vapor pressure decreases, but during this time, a re-electromotive voltage is applied between the electrodes, so the vapor pressure is reduced to a level sufficient to withstand this increase in the re-electromotive voltage. Otherwise, the current will not be successfully cut off.

In the case of metal, the following equation is often used to express the change in metal vapor density n after the current zero point, where n() is the initial density at the current zero point.

1 1 L 1 n=nO[:1-exp(--2)') erf[-(-
) −]−−(1)α 2 Rα α=t−(21 horses ・・・・・・・・・・・・・・・
...(2)M where R: electrode radius, M: mass of metal atom, K: Boltzmann's constant, T: temperature of metal atom, L: '(If, polar interpolation length.

Initial value n. is given by the following formula.

Here, ω==2πfS f: frequency, Irn++s
: L or cut-off current value (effective value) E: Evaporation coefficient.

As is clear from the above theoretical formula, the breaking performance of a vacuum breaker greatly depends on the interest characteristics of the contact material as well as the geometric configuration of the electrodes.

However, according to the results of tests and research on various types of contact materials, it has been found that the above theory cannot be applied to Ag-WC type contact materials1. In other words, the Ag-WC type contact material is generally a sintered alloy produced by press-molding WC powder, firing it to obtain a sintered body with voids, and then infiltrating it with Ag. , the breaking performance is 1
A with a lower melting point than WC, which is a thick and thick component
It depends heavily on the g component, and the residual metal vapor at the current zero point cannot be used to image the entire alloy. This is one reason why the above theory is difficult to apply. This means that Ag-W
The stable arc voltage of the C type contact is 2O-30V, and Cu
This is lower than the arc voltage of 40 to 80 V for melt-type contacts (for example, Cu-B+), which are mainly made of Cu-B+, and is also related to the fact that the stable range of the arc voltage is narrow. Furthermore, when we conducted an arc observation study on Ag-WC contacts, we found that in the current cutoff limit region, a large amount of red-hot metal particles were scattered apart from the arc column.

This is thought to be due to the scattering of WC particles due to the destruction of interparticle bonds, whereas the arc is the ionization of metal vapor mainly composed of Ag. Therefore, the limit of the breaking performance cannot be determined by applying the conventional theory described above that only considers the eel of residual metal vapor and its diffusion, but also needs to be determined by taking into account the destruction of the bonds between particles of WC. be.

In any case, for the reasons mentioned above, Ag-WC
When the breaking characteristics of the Cu-based contact material were compared with those of the Cu-based contact material, they were far inferior, as shown in FIG. 2, which shows a comparison of the breaking current limit performance.

[Purpose of the invention]

An object of the present invention is to improve the breaking characteristics of Ag-WC type contacts and to make it possible to provide a large-capacity vacuum breaker that does not require an external surge absorber.

[Summary of the invention]

In the course of research to achieve the above-mentioned object, the present inventors noticed that, as described above, Ag-WC contact materials are accompanied by a different breaking phenomenon than Cu-based contact materials. Therefore, if used in an electrode that functions on a different breaking principle, the Ag-WC contact material may also exhibit good breaking characteristics. Therefore, based on this idea, we applied an Ag-WC contact material to a so-called vertical magnetic field electrode, which has recently been put into practical use and applies a magnetic field in parallel with the arc, and measured its breaking current limit performance. However, the result is
As shown in FIG. 3, it was applied to a conventional flat plate electrode.

Although there is a slight improvement compared to Nariai, the conventional C6
Even compared to flat plate electrodes using system contacts, the performance was still considerably inferior.

However, this was later confirmed that the above measurement was performed with the electrical property of Gauss/IB (IB is the peak value of the rated breaking current and the unit is KA), which is the appropriate magnetic field for Cu or Cu-based contact materials. This value corresponds to Ag-W with different cut-off phenomenon.
This was thought to be due to the fact that it could not be applied to C-based contact materials. Therefore, as a result of conducting various experiments by changing the magnetic field strength, we found that the magnetic field strength was
By selecting A or more, Ag-
It has been found that the current breaking performance of a WC-based contact can be dramatically improved, and that the current breaking performance of a conventional Cu-based contact can be obtained. This is thought to be due to the fact that the strength of the magnetic field was made stronger than before, thereby increasing the limitation of destruction of the interparticle bonds of the bamboo shoots.

The vacuum breaker of the present invention is based on the above-mentioned knowledge. More specifically, the vacuum breaker of the present invention is based on the axial direction of the arc column. Gauss/IB (peak value of rated breaking current).

It is characterized in that it has a vertical magnetic field electrode equipped with a coil electrode that applies a magnetic field of unit KA) or more, and that the contact point of this vertical magnetic field electrode is made of an Ag-WC based sintered alloy.

[Embodiments of the invention]

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

FIG. 5 is a structural diagram of a vacuum breaker showing an embodiment of the present invention, FIG. (,) is a sectional view taken along line BB in the arrow direction. Referring to FIGS. 5 and 6, vacuum pulp 3 is placed in a vacuum container 4, which is made of an insulating material such as ceramic and has a substantially cylindrical shape, and whose both ends are closed with end plates 5a and 5b. A pair of electrodes 6a and 6b are arranged.

A fixed shaft 7& is connected to one electrode (fixed electrode) 6a, and this fixed shaft 7a hermetically penetrates the end plate 5a and projects to the outside. The other electrode (movable electrode) 6bK is connected to a movable shaft 7b, which is attached to the end plate 5b via a bellows 8, and opens and closes the pair of electrodes while maintaining the vacuum in the vacuum container. It makes it possible. On the other hand, an arc shield 9 is arranged in the vacuum container so as to surround the electrodes 6a and 6b, and when the current is switched on and off, the arc shield 9
This prevents the inner wall of the insulating container 4 from being contaminated by metal vapor generated from the insulating container 4. The electrodes 6m and 6b have contacts 10a and 1Ob whose contact surfaces are made of Ag-WC sintered alloy,
It is composed of coil electrodes 11a and llb provided behind it, and has a structure in which a magnetic field parallel to the arc is applied when current is switched on and off, that is, a so-called vertical magnetic field electrode structure. According to the invention, this coil electrode 11a, l
lb), one having a capacity that provides a magnetic field strength of 50 Gauss/IB or more is used.

Also, the coil 11a is in contact with the back surfaces of the contacts 10a and 10b, and
.

Inside the reinforcing plate 11b, there is a reinforcing plate 1 made of a material such as aluminum or stainless steel that does not easily affect the magnetic field generation strength.
2 is arranged to prevent the contacts 10a * 10b from being deformed or cracked due to impact or mechanical stress during current switching.

According to the above configuration, since a magnetic field parallel to the arc is applied when the current is cut off, the arc voltage can be kept low, and since the arc spreads uniformly between the contacts 10a and 1Ob, local overheating of the contacts 10a and 10b is prevented. Since the current density on the surface can be kept low, it is possible to cut off large currents. In particular, since Ag-WC sintered alloy is used for the contacts 10a and 10b, it has excellent low surge characteristics, and because the coil electrode is made of a material that provides a large magnetic field strength, the Ag-WC contacts can be broken. performance is significantly improved.

The improvement in breaker performance obtained by the vacuum breaker of the present invention is also shown in FIG. 4, and can be seen from the results in Table 1 below. In other words, Table 1 shows the results of comparative verification of the breaking performance due to differences in contact materials and electrode configurations when the outer diameter dimensions of the electrode parts are the same. Shut off? < indicates a comparative value when the flow limit is set to 100 inches. Note that the values in the table are values when the recovery voltage during the cutoff test was set to 1.2 KV or less.

Further, in the column of contact material composition, the numbers in 0 mean weight %.

Table 1 In the above table, No. 3 is an example of the present invention, and looking at the results in the table, the same result can be achieved by incorporating an Ag-WC sintered alloy contact into a longitudinal magnetic field electrode with a magnetic field strength of Gauss/KA or higher. Not only spiral electrodes with C11-
It can be seen that improved breaking performance is obtained compared to the spiral contact incorporating the T@ contact.

In the above example, an Ag-WC sintered alloy having a composition of 30% Ag-WC balance is used, but as a contact material in the vacuum breaker of the present invention, generally 5 to 50% by weight of Ag is required. Depending on Fe1N1, Co5B
1. An Ag-WC based sintered alloy is generally used, in which elements such as PbSSb and To are added in an amount of 5% by weight or less, and the remainder consists of WC as a main component.

In addition, although the embodiment shown in Fig. 5 shows the case where the arc shield 7 is supported in the middle of the insulating container, the arc generated between the electrodes due to the arc control effect due to the generation of a vertical magnetic field when the current is cut off is transferred to the arc shield. Since it is difficult to touch, differences in the way the arc shield is supported have little effect on the breaking performance. Therefore, the same effect can be obtained even if the arc shield 7 is fixed to either one of the end plates 5a and 5b.

〔Effect of the invention〕

As described in detail above, according to the present invention, Ag-WC sintered alloy contacts, which have low surge characteristics but are not used as contacts in large-capacity circuit breakers due to poor breaking performance, can be replaced with 50
By incorporating it into a vertical magnetic field electrode that generates a large magnetic field strength of Gauss/I, the breaking performance can be dramatically improved, resulting in a vacuum breaker with a large breaking capacity that does not require an external surge absorber. It becomes possible to provide

[Brief explanation of the drawing]

Figure 1 is a plan view of a conventional sub-electrode, Figures 2 to 4
The figures are breaking current limit diagrams for various electrode configurations and contact materials, FIG. 5 is a front sectional view of a vacuum breaker according to an embodiment of the present invention, and FIG. 6(a) is a diagram of a vacuum breaker according to an embodiment of the present invention. A plan view (contact surface) of the electrode used, FIG. 6(b) is a sectional view taken along the line B--B in FIG. 6(-). 1... Contact, 2... Electrode, 3... Vacuum valve, 4
... Insulating container, 5a, 5b... End plate, 6a, 6b.
... Vertical magnetic field electrode, 7a, 7b... Conductive axis, 8... Bellows, 9... Arc shield, 10. loa,
lOb...Contact, 11! 11a+11b...Coil electrode, 12...Reinforcement plate. Applicant's agent Kiyoshi Inomata Figure 6 (Q)

Claims (1)

[Claims] It has a vertical magnetic field electrode equipped with a coil electrode that applies a magnetic field of Gauss/IB (peak value of rated breaking current, unit KA) or more in the axial direction to the arc column, and the contact point of this vertical magnetic field electrode is A vacuum breaker characterized by being constructed of an ArWC-based sintered alloy.