JP2002270071A - Vacuum circuit breaker, and vacuum valve and electric contact used for the vacuum circuit breaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode with a high strength, a small secular change, and a high reliability, a method of manufacturing the electrode, a vacuum valve using the electrode, and a vacuum circuit breaker using the vacuum valve. SOLUTION: This vacuum circuit breaker comprises a fixed side electrode having an arc electrode, an arc electrode support member supporting the arc electrode, and a coil electrode arranged continuously with the support member and a movable side electrode. The arc electrode, arc electrode support part, and coil electrode are formed of non-connection parts and formed integrally with each other by welding. In particular, the arc electrode support part and coiled electrode are formed with a Cu alloy containing at least one of Cr, Ag, W, V and Zr of 0.05 to 2.5 w.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel vacuum circuit breaker, a vacuum valve used for the same, an electric contact used for the same, and a method for manufacturing the same.

[0002]

2. Description of the Related Art An electrode structure in a vacuum circuit breaker includes a pair of fixed electrodes and a movable electrode. The structure of the fixed and movable electrodes includes an arc electrode, an arc supporting member supporting the arc electrode, a coil electrode material connected to the arc supporting member, and an electrode rod at an end of the coil electrode. I have.

[0003] The above-mentioned arc electrode material is directly exposed to an arc to open and close a high voltage and a large current. Satisfactory characteristics required of the arc electrode are a large breaking capacity and a high withstand voltage value. That the contact resistance value is small
(Excellent electrical conduction), excellent welding resistance, low contact wear, and small cutting current value. However, it is difficult to satisfy all of these characteristics, and in general, a material that emphasizes particularly important characteristics according to the application and sacrifices other characteristics to some extent is used. As a material for an arc electrode for interrupting a large current and a high voltage, Japanese Patent Application Laid-Open No. 63-96204 discloses a method of infiltrating Cu into a Cr or Cr-Cu skeleton. A similar manufacturing method is disclosed in Japanese Patent Publication No. 50-2167.
It is also disclosed in Japanese Patent Publication No. 0.

On the other hand, the arc electrode supporting member has a function of generating a vertical magnetic field by devising the shape of the supporting member together with the role of a reinforcing member of the arc electrode. The material used is pure Cu having good conductivity.

[0005] Further, as disclosed in Japanese Patent Publication No. 3-17335, the coil electrode material also has a role of an arc electrode and a reinforcing member of a support member. By doing so, a vertical magnetic field is generated in the arc electrode, and the arc generated in the arc electrode due to the vertical magnetic field is diffused throughout the arc electrode, and is forcibly interrupted. The material used is pure Cu as well as the arc support member.

On the other hand, the manufacturing process of the electrode composed of the arc electrode, the arc electrode supporting portion, the coil electrode and the electrode rod includes the manufacturing and machining of the arc electrode material, the arc electrode supporting member, the coil electrode material and the electrode rod. The electrodes are completed through the steps of machining, assembling each part, and brazing.

[0007] The above-described method for manufacturing an arc electrode includes a Cr powder, a Cu powder, a W powder, a Co powder, a Mo powder, a W powder, a V powder,
The so-called infiltration method, in which Nb powder or an alloy powder thereof is formed into a predetermined composition, shape and porosity and then sintered, and then the molten skeleton of the sintered body is impregnated with Cu or alloy melt, or sintering before infiltration. The arc electrode material manufactured by the so-called powder metallurgy method in which the density is set to 100% in the process is further machined into a predetermined shape.

The arc electrode support, the coil electrode, and the electrode rod are each cut out of a pure Cu material into a predetermined shape designed to easily generate a vertical magnetic field.

[0009]

The parts machined after infiltration are assembled and brazed to form a series of electrode structures. However, in the brazing method, a brazing material having good wettability is put between the arc electrode, the arc electrode support, the coil electrode and the electrode rod, and the temperature is raised in a vacuum or in a reducing atmosphere. Electrodes constructed using brazing are extremely time-consuming and time consuming to machine the components and to align the parts during the assembly of parts for brazing. As a result, electrode materials may be broken or fall off due to poor brazing. As described above, the electrode structure manufactured by the conventional method has uniform electrode material characteristics,
Poor reliability and safety.

Recently, along with the development of materials, attempts have been made to open and close large currents and high voltages in terms of design specifications of vacuum circuit breakers. As an example, the breaking performance is improved by increasing the opening / closing breaking speed. But,
By increasing the breaking speed, an impact force is applied to the entire electrode when the contact force between the arc electrodes is increased and the electrode is opened and closed, and the electrode material is deformed over time. Generally, a high-strength arc electrode material having excellent breaking characteristics or welding characteristics is used for the arc electrode material, but pure Cu is used for the arc support member, the coil electrode material, and the electrode rod. Pure Cu
The material has a very small proof stress, and furthermore, as described above, a groove is formed in the cross section for the purpose of generating a vertical magnetic field, and especially it can not withstand shocking stress and deforms over time. Become. Deformation of the electrode member causes inconvenience of the electrode opening / closing operation, welding failure of the arc electrode, destruction and dropping of the arc electrode, and hinders opening / closing operation in an emergency.

An object of the present invention is to provide a vacuum circuit breaker provided with a highly reliable electrode which is less likely to deform with time, a vacuum valve used therefor, an electric contact used therefor, and a method of manufacturing the same.

[0012]

According to the present invention, there is provided a vacuum valve provided with a fixed electrode and a movable electrode in an insulating container, and each of the fixed electrode and the movable electrode in the vacuum valve has the above-mentioned structure. In a vacuum circuit breaker provided with a conductor terminal connected outside the vacuum valve and an opening / closing means for driving the movable-side electrode via an insulating rod connected to the movable-side electrode, the fixed-side electrode and the movable-side electrode Is an arc electrode made of an alloy of a refractory metal and a highly conductive metal, an electrode support portion made of a highly conductive metal for supporting the arc electrode, and the support portion electrically connected to the conductor terminal and the high electrode. It has an electrode rod made of a conductive metal and a vertical magnetic field generating coil connected to the electrode support, and the arc electrode, the electrode support and the electrode rod or the magnetic field generating coil are formed by melting the highly conductive metal. Being integrally formed In a vacuum circuit breaker according to claim.

The arc electrode is made of Cr, W, Mo and Ta.
And an alloy of a highly conductive metal of Cu, Ag or Au or a highly conductive alloy mainly composed of these, and the electrode supporting portion is formed of the highly conductive metal or alloy. It preferably comprises

Further, the arc electrode is made of an alloy containing one or more of Cr, W, Mo and Ta in a total amount of 50 to 80% by weight and Cu, Ag or Au in a content of 20 to 50% by weight. The support is Cr, Ag, W, V, Nb, M
It is preferable that one or more of o, Ta, Zr, Si, Be, Ti, Co, and Fe be composed of an alloy of Cu, Ag, or Au with a total amount of 2.5% by weight or less.

The arc electrode according to the present invention is made of a composite alloy of a highly conductive metal impregnated in a porous refractory metal, and the arc electrode and the electrode support are integrally formed by melting the highly conductive metal. Is preferred.

In the present invention, the electrode supporting portion and the electrode rod or the magnetic field generating coil have a 0.2% proof stress of 10 kg / mm ² or more,
The specific resistance shall be 2.8 μΩcm or less.

In the present invention, at least one of the fixed side electrode and the movable side electrode is provided with an electrode rod or a vertical magnetic field generating coil made of a highly conductive metal on the electrode support.

The vertical magnetic field generating coil can be integrally formed by brazing to the electrode support or by melting and solidifying the highly conductive metal.

The vertical magnetic field generating coil has a shape in which a slit groove is provided in the circumferential surface of the cylindrical shape and a shape in which the cross section is substantially swastika.

There are three sets of the vacuum valves for three phases, and it is preferable that the three sets of vacuum valves are arranged side by side and integrated integrally by a resin insulating cylinder.

According to the present invention, there is further provided a vacuum valve having a fixed side electrode and a movable side electrode in an insulating container maintained in a high vacuum, wherein the two electrodes are a composite member of a refractory metal and a highly conductive metal. An arc electrode made of a highly conductive metal supporting the arc electrode, an electrode rod connected to the support and made of the highly conductive metal, and a vertical connected to the electrode support. A vacuum valve having a magnetic field generating coil, wherein the arc electrode and the electrode support are integrally formed by melting the highly conductive metal.

The configuration of the electrodes of the vacuum valve and the magnetic field generating coil according to the present invention is the same as described above.

According to the present invention, there is provided an arc electrode made of an alloy of a refractory metal and a highly conductive metal, an electrode support portion made of a highly conductive metal for supporting the arc electrode, and the electrode portion connected to the support portion. An electrode contact is characterized in that an electrode rod made of a conductive metal and a vertical magnetic field generating coil connected to the electrode support are integrally formed by melting the highly conductive metal.

The configuration of the arc electrode of the electric contact in the present invention is the same as described above.

According to the present invention, there is provided an arc electrode made of an alloy of a refractory metal and a highly conductive metal, an electrode support portion made of a highly conductive metal for supporting the arc electrode, and the electrode portion connected to the support portion. In a method of manufacturing an electrical contact having an electrode rod made of a conductive metal and a vertical magnetic field generating coil connected to the electrode support, the arc electrode is provided on a porous sintered body having a refractory metal with the high conductivity. A conductive metal is placed, and the highly conductive metal is formed by melting and infiltrating the porous body, and the electrode support and the electrode rod or the magnetic field generating coil remain after the infiltration. A method of manufacturing an electrical contact, characterized in that the electrode is formed by setting the thickness of a highly conductive metal to a thickness required for the electrode support.

Further, according to the present invention, the arc electrode and the electrode supporting portion are formed by infiltrating and solidifying the high-conductive metal and then maintaining the desired temperature to obtain a supersaturated solid in the high-conductive metal. It has a heat treatment step of precipitating the dissolved metal or intermetallic compound.

The electric contact can be used as a fixed electrode or a movable electrode of a vacuum valve.

According to the present invention, the electrode supporting portion has a vertical magnetic field generating coil made of a highly conductive metal, and the thickness and shape of the highly conductive metal remaining after infiltration into the porous body are determined by the electrode supporting portion. It can be formed by melting and solidifying according to the shape of the part and the electrode rod or the vertical magnetic field generating coil.

The electrode structure of the vacuum circuit breaker comprises an arc electrode, an arc electrode support member and an electrode rod, and if necessary, a coil electrode. The arc electrode is made of a composite alloy of a refractory metal and a conductive metal, and the former includes Cr, W, M
A metal having a high melting point of about 1800 ° C. or higher such as o, Ta or the like is used, and a metal having a small solid solution amount of 3% or less with respect to Cu, Ag, and Au as highly conductive metals is preferable. Pure Cu is particularly preferable for the arc electrode supporting member, the coil electrode material and the electrode rod. However, since the strength is low, as a measure for preventing the deformation of these members, it is reinforced with pure iron or stainless steel of an iron-based material to prevent the electrode from being deformed. I'm working.

The refractory metal is 50 to 80% by weight, especially 55 to 80% by weight.
An alloy containing 65% by weight and 20 to 50% by weight of Cu, Ag or Au, and particularly the former porous sintered body or a porous sintered body containing a small amount of 10% by weight or less of a highly conductive metal. Is preferably used as a composite material impregnated with a polymer.

The arc electrode and the electrode support have a two-layer structure, and the electrode support reinforces and supports the arc electrode.
The thickness is preferably at least half that thickness, and particularly preferably at least the same thickness. The porous sintered body preferably has a porosity of 50 to 70%. As a refractory metal, in particular, it is preferable to use 1
It may contain one or more of Nb, V, Fe, Ti and Zr in an amount of up to 10% by weight.

The coil electrode can be manufactured by the same method as the casting technique at the same time as brazing or infiltrating the porous refractory metal together with the electrode support portion with the highly conductive metal. The electrode support member and the coil electrode material can be configured as a monolithically continuous structure. As a result,
Reduction of machining process of each member and assembly process of each member at the time of brazing. Also, non-joining causes problems such as the extreme heat generation of the conventional brazing part, breakage and falling off of the arc electrode material due to poor brazing. Disappears. When the coil electrode is formed by brazing, a composite material in which ceramic particles are dispersed can be used.

Further, according to the present invention, the arc electrode material, the arc electrode support member and the coil electrode material constituting the electrode are:
An arc electrode supporting member and a coil electrode material can be obtained in the same process as in the manufacture of an electrode having a monolithic structure, and at the same time, a Cr-A content of 0.01 to 2.5% by weight can be obtained.
g, W, V, Zr, Si, Mo, Ta, Be, Nb, T
Au, Ag, and Cu containing one or more of i can be used. Therefore, the mechanical strength, particularly the proof stress, can be greatly increased without significantly lowering the electric conductivity of the arc electrode support member and the coil electrode material. As a result, it is possible to sufficiently cope with an increase in the contact pressure between the electrodes and the impact force at the time of opening and closing the electrodes, and it is possible to solve temporal deformation.

As described above, the arc electrode material, the arc electrode supporting member, and the coil electrode material are not joined to each other, and have a metallographically continuous integrated structure. And a highly reliable and safe vacuum circuit breaker in which the adverse effects are eliminated as compared with the above electrode structure.

According to the present invention, Cr, W, Mo, Ta powder or Cu, Ag, Au powder or any other metal particles are mixed into a predetermined composition, and the mixed powder is adjusted to a predetermined void content. Then, after being molded, it is sintered to form a porous sintered body. Thereafter, a block made of pure Cu, Ag, Au, or an alloy thereof is placed on the sintered body and melted to infiltrate the voids of the porous sintered body with a metal such as pure Cu or a Cu alloy. At this time, the molten infiltrant is alloyed to have the above-mentioned content by positively utilizing the liquid phase diffusion of the constituent elements of the sintered body into the molten infiltrant. The ingot after completion of infiltration is processed into an electrode having a predetermined shape.

In the infiltration of a highly conductive metal, the amount of the porous metal dissolved in the highly conductive metal can be controlled by the infiltration temperature and the holding time. Is set in consideration of the temperature. Of course, an alloy in which an alloy element is added to a highly conductive metal in advance can also be used. As a result, a material having high strength and a low specific resistance can be obtained, so that a material having high performance can be obtained.

As described above, the electrode in the present invention can be formed in a desired shape by a combination of infiltration and casting techniques, but can be obtained by cutting as the final shape described above.

Vacuum circuit breakers are used together with disconnectors, grounding switches, lightning arresters, and current transformers, and are used for high-rise buildings, hotels, intelligent buildings, underground shopping centers, petroleum complexes, various factories, stations, hospitals, halls, subways, and water and sewage systems. It is used as a high-voltage receiving and transforming equipment that is indispensable as a power source for public facilities and the like.

[0039]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 (a) shows a cross section of an ingot of an electrode having a monolithic structure which is experimentally produced by the method of the present invention. In the figure, 1 is an arc electrode material,
Reference numeral 2 denotes an arc electrode support member, and reference numeral 3 denotes a member for supplying Cu for infiltration and a feeder.

After mixing 5% by weight of Cu powder and 95% by weight of Cr powder with a V-type mixer, using a mold having a diameter of 80 mm, a molding pressure of 1.5 ton / cm ² , a diameter of 80 mm and a thickness of 9 mm.
Was formed. The molded body was sintered in a hydrogen atmosphere at a sintering temperature of 1200 ° C. for 30 minutes. The porosity of the sintered body at this time is 65%. Next, FIG. 1B is a diagram showing a method of manufacturing an electrode, and as shown in FIG.
The sintered body 6 is placed at the center of the bottom surface of a graphite container 5 having an inner diameter of 90 mm, an outer diameter of 100 mm and a height of 100 mm on which a 5-mesh alumina powder 4 (Al ₂ O ₃ ) is spread to about 10 mm, and has a diameter of 80 mm made of pure Cu. An infiltration material 7 serving as an arc electrode supporting portion and a coil electrode portion having a thickness of 15 mm was placed on the same center as the sintered body 6. Next, an infiltrant having a diameter of 28 mm and a length of 25 mm and a feeder 8 made of Cu forming a feeder portion are placed on the same center as the infiltrant 7. The graphite container 5 is filled with an infiltrant 7 made of pure Cu, a feeder 8 and alumina powder 9.

The infiltration conditions are as follows: the vacuum is maintained at 1,200 ° C. for 90 minutes in a vacuum of 1 × 10 ⁻⁵ Torr or less. After the hot water 8 is melted and the infiltration material is uniformly soaked into the skeleton of the sintered body 6, it is allowed to cool and solidify in a vacuum atmosphere. FIG. 1A is a cross-sectional appearance of an ingot taken out of a graphite container after solidification. Further, FIG. 1 (c) shows the arc electrode 1 and the arc electrode support 2 after cutting, and as a result of observing the interface between the two with a microstructure photograph, Cu was infiltrated into the pores of the Cr sintered body. It became clear that.

As described above, according to the method of the present invention, FIG.
Also, as can be seen from FIG. 1 (c), it can be seen that an electrode having an integral structure of the arc electrode, the arc electrode support, the electrode rod or the coil electrode can be sufficiently manufactured. The arc electrode and the electrode support have the same thickness. Further, the interface between the arc electrode material and the arc electrode supporting member is completely integrated in a metallographic manner, and it can be seen that joining by brazing or the like is unnecessary.

FIG. 2 shows three molds of the mold of FIG. 1B, and three molds can be manufactured at a time. A similar technique can be implemented for the second embodiment. Not only three but also a desired number can be manufactured at a time.

Example 2 FIG. 3 shows an infiltrated state and an electrode shape manufactured using the ingot. The infiltration conditions are almost the same as in Example 1.

In No. 2, the length of the graphite container 5 was set to 150 mm and the length of the arc electrode support member and the coil electrode member 11 was set to 45 mm in comparison with the first embodiment. The infiltration hold time is
The time was set to 120 minutes, and the other conditions were the same as in Example 1. (A) and (b) type electrodes were produced from the ingot thus obtained. That is, the type (a) has the arc electrode 12, the arc electrode support portion 13, and the coil electrode material 14 integrally formed, and the electrode rod 15 is joined 16 by brazing. Also,
The type (b) has a reinforcing member 17 made of pure Fe at the center of the type (a). The reinforcing member 17 is brazed to the electrode support 13 and the electrode rod 15, respectively.

No. 3 was infiltrated with respect to No. 2 with the shape of the arc electrode supporting member and the coil electrode member 19 being concave, and excluding the infiltration Cu supply and the feeder member 18. From the ingot of No. 3, an electrode shape of (a) type was manufactured.

For No. 4, the length of the infiltration Cu supply and feeder member 20 was set to 100 mm and the length of the graphite container 5 was set to 200 mm with respect to No. 2. An electrode of type (c) was produced from the ingot of No. 4. The electrode of the (c) type can have an integral electrode structure including the electrode rod 22 without using brazing. From the ingot of No. 3, in addition to the (c) type, the (a) and (b) type electrode structures can be produced by cutting.

In No. 5, a trumpet-shaped iron core was inserted toward the sintered body 26 at the center of the arc electrode support member and the coil electrode member 23 and the supply and feeding member 24 of Cu for infiltration with respect to No. 4. Things. This iron core is higher than the melting point of Cu, and does not care about the shape. From the ingot of No. 5, (d) type and (e) type electrodes were produced.

The (d) type electrode has a shape in which a reinforcing member 27 is cast in the center of the (c) type electrode.

The (e) type electrode is a reinforcing member 1 of the (b) type electrode.
It is an electrode in which an iron core is cast in place of 7.

From the above results, the dimensions of the ingot and the dimensions before the infiltration were measured. As a result, the dimensions of the arc electrode supporting member and the coil electrode member were changed between the state before the infiltration and the ingot after the infiltration. There were few dimensional differences. On the other hand, as a result of measuring the dimensions of the feeder member, the ingot size after infiltration was reduced to 10 mm compared to 25 mm before infiltration. As described above, the first condition for achieving the present invention is that the arc electrode supporting member and the coil electrode member and the Cu or Cu alloy supply and feeder member for infiltration have a double structure.

In order to obtain a sound and desired ingot size, it is important to control the cooling rate of the ingot. It is necessary to make the cooling rate at the upper part of the ingot higher than that at the side of the ingot. As a second condition for achieving the present invention, ceramic particles which have a large specific heat, such as alumina (Al ₂ O ₃ ), and do not react with the molten Cu are suitable as a heat retaining agent for increasing the cooling rate of the upper part of the ingot. If the ceramic particle size at this time is too large or too small, the molten metal flows through between the ceramic particles and does not serve as a mold. The optimal particle size is between 20 mesh and 325 mesh. Also, the required amount of ceramic particles to keep warm is
The thickness is required to be 2/3 or more of the diameter size of the target ingot.

Example 3 Table 1 shows the results of analyzing the amount of Cr in the ingot when the infiltration temperature was variously changed in the infiltrated No. 2 of Example 2 and the sintered body. 6 shows the results of analyzing the respective composition elements in the ingot when the respective compositions of the arc electrode support member 6 and the coil electrode member 11 were changed. The Cu supply for the molten metal and the feeder 8 have the same composition.

No. 6 to No. 8 indicate the composition Cr of the sintered body 6
-5 Change the infiltration temperature when pure copper is infiltrated into Cu material.
This is the amount of Cr in the ingot when held for 20 minutes. Infiltration temperature
The ingot composition at 1250 ° C is C containing 1.65% Cr.
It turns out that it becomes a u alloy. No. 9, 10, 14, 1
5, 16 and 18, the compositions of the sintered body 6 are fixed at Cr-5Cu, and the compositions of the infiltrant are Cu-Ag and Cu-Z, respectively.
It is an elemental analysis result in an ingot when r, Cu-Si, Cu-Be alloy is used. It can be seen that each ingot becomes a ternary Cu alloy containing about 0.6% Cr.

In Nos. 11, 12, 13, and 17, the compositions of the infiltration material 7 and the feeder 8 were made pure Cu, and the composition of the sintered body 6 was V, Nb, V, Nb, W in Cr-5Cu. 5 shows the results of elemental analysis in an ingot when adding iron. V,
It can be seen that the contents of Nb and W are 0.02% or less, and the ingot composition is a Cu alloy containing about 1.0% Cr.

[0056]

[Table 1]

Table 2 shows that the arc electrode (composition: 59% by weight C)
r-41 wt% Cu) and a pure Cu material are brazed by a conventional method (condition: 800 ° C., vacuum, Ni-based brazing material).
In this case, the electrical resistance and strength of the joined portion were measured (Comparative Example 1), the electrical resistance value of pure copper annealed at 800 ° C. (Comparative Example 2), and Nos. 6 to 18 were obtained. It shows the electrical resistance and strength measurement results of the ingot. The electric resistance was measured by a four-point resistance measuring method, and the strength was measured by using an arm slash tensile tester.

[0058] Conventional bonded brazing in a manner (Comparative Example 1) strength of the interface is 22~12kg / mm ² and the variation is large, the test piece strength 12 kg / mm ² failure portion braze was observed. The electric resistance including the interface is 4.82 μΩ · cm.
And about 3 to 4 times higher resistance than pure copper material (Comparative Example 2). On the other hand, the interface strength of No. 6 is 24 to 25 kg / m
The test piece showed a stable strength of m ^2, and no defect was observed on the test piece. Further, in the embodiment of the present invention, the electric resistance including the interface cannot be measured. Although the mating material of the arc electrode of Comparative Example 1 was pure Cu and the mating material of No. 6 was a Cu alloy containing about 0.62% of Cr, there was no interface, so the specific resistance was 1. 95 μΩcm, which is lower than Comparative Example 1. This indicates that the resistance value at the interface of the brazed joint in the prior art is very large.

On the other hand, the strength of pure Cu of Comparative Example 2 was the maximum value of 2
0.2% proof stress to 2~23kg / mm ² is 4~5kg / mm ²
It can be seen that, when used as an arc electrode support member or a coil electrode material, it cannot withstand an impact load and is deformed with time. In contrast, C
r or the Cu alloys containing Ag, V, Nb, Zr, Si, W, and Be, respectively, have electrical resistance values of about 1.5 to 2.0 times as compared to pure annealed Cu. However, when compared with the resistance value of the brazing joint interface of the prior art, it is about half or less, so that it can be sufficiently used as an electrode material for an actual vacuum circuit breaker. The strength of Nos. 7 to 18 was 22 to 25 kg / mm ^{2 at the} maximum strength, which was not much different from that of pure Cu, but was 10 to 14 kg / mm at a 0.2% proof stress value.
^The strength is improved twice and twice.

As described above, Cr or A according to the present invention is used.
The arc electrode supporting member, coil electrode material and electrode rod made of Cu alloy containing g, V, Nb, Zr, Si, W and Be, respectively, are not deformed due to repetitive impact loads when the electrode is opened and closed. Thus, welding failure due to the above is prevented to improve reliability and safety.

[0061]

[Table 2]

FIG. 4 is a graph showing the relationship between the infiltration temperature and the amount of Cr dissolved in the infiltration material from the porous Cr sintered body.
As shown in the figure, by increasing the infiltration temperature, the amount of Cr in the infiltration material can be increased. Further, a desired amount of Cr can be determined by the infiltration temperature.

FIG. 5 shows the relationship between the content of alloying elements in Cu and
It is a diagram which shows the relationship with 2% proof stress. As shown in the figure, it is clear that both the content of Cr alone and the alloy containing Cr and other elements are strengthened by increasing the content. Further, an alloy containing Cr together with another element has higher strength than Cr alone, even at the same total content. The content of each element is 0.1% Ag, 0.1% Zr, 0.1% Si.
%, Be 0.05%, Nb, V, and W are each 0.01% or more, whereby a yield strength of 10 kg / mm ² or more can be obtained.

FIG. 6 is a diagram showing the relationship between the 0.2% proof stress and the specific resistance. As shown in FIG. 4, since the specific resistance increases along with the strength by increasing the total solid solution amount in Cu, it is necessary to reduce the increase in the specific resistance and improve the strength by using other elements than Cr alone. It turns out that it can be obtained by adding. In particular, other than Si, the specific resistance is small and high strength can be obtained. In particular, a 0.2% proof stress of 10 kg / mm ² or more and a specific resistance of 1.
It is preferably from 9 to 2.8 μΩcm.

FIG. 7 shows Cr, Si, Be, Zr, Ag, N
It is a diagram which shows the relationship between b, V, W amount, and specific resistance. The specific resistance increases with the addition of alloying elements, but the electrode resistance during energization can be kept low by reducing the specific resistance of the electrode support and coil electrode as much as possible. Needs to be cooled through the electrode rods, and the heat conductivity needs to be increased, so that the heat conductivity can be kept high. In the present embodiment, the desired specific resistance can be roughly determined from the figure. When Cr is used as the arc electrode, the content of each element is set to 0.5% for Si, 0.5% for Be, 1.5% for Zr,
g2.5%, Nb, V and W are each preferably contained in an upper limit of 0.1%. 3.0μΩcm as specific resistance
It is preferable to set the following.

Embodiment 4 FIG. 8 is a sectional view of a vacuum bulb using an arc electrode according to the present invention.

An upper and lower end plate 38 is integrally formed at upper and lower openings of a vacuum vessel 35 made of an insulating cylinder formed of an insulating material.
a and 38b are provided to form a vacuum chamber, and a fixed-side electrode rod 34a that forms a part of the fixed electrode 30a is provided vertically in the middle of the upper end plate 38a. A vertical magnetic field generating coil 33a and an arc electrode 31a are provided on a rod 34a, and a movable electrode rod 34b forming a part of the movable electrode 30b is formed in the middle of the lower end plate 38b located immediately below the fixed electrode 30a. The movable-side electrode rod 34b is provided with a vertical magnetic field generating coil 33b and an arc electrode 31b of the same size as the vertical magnetic field generating coil 33a and the arc electrode 31b, and is provided with respect to the arc electrode 31a of the fixed electrode 30a. The movable electrode 30b is brought into contact with and separated from the arc electrode 31b, and the movable electrode rod 34b is
A metal bellows 37 is provided so as to extend and contract inside the lower end plate 38b positioned around the lower end plate 38b, and a cylindrical metal plate shield member 36 is formed around the two arc electrodes. The shield member 36 is provided by a vacuum vessel 35 formed of an insulating cylinder, and is configured so as not to impair the insulation of the insulating cylinder.

Further, the arc electrodes 31a, 31b are connected to the arc pole supporting portions 32a, 32 obtained by the above-described infiltration.
2b, and each of the longitudinal magnetic field generating coils 33a, 33
b is reinforced by brazing members 39a and 39b made of pure iron and brazed. Austenitic stainless steel is used as the reinforcing members 39a and 39b. Glass and ceramic sintered bodies are used for the vacuum container 35 formed of an insulating cylinder. The vacuum vessel 35 composed of an insulating cylinder is brazed to metal end plates 38a and 38b via an alloy plate having a thermal expansion coefficient close to that of glass such as Kovar or ceramics.
0 ^-6 mmHg is maintained below the high vacuum.

The fixed electrode rod 34a is connected to a terminal,
It becomes a current path. The exhaust pipe (not shown) is the upper end plate 38a.
And connected to a vacuum pump when exhausting. The getter is provided to absorb a small amount of gas generated inside the vacuum vessel and maintain the vacuum. Shield member 36
Has a function of adhering and cooling metal vapor on the main electrode surface generated by the arc, and has a function of maintaining a degree of vacuum having a getter function.

FIG. 9 is a sectional view showing details of the electrodes. Both the fixed electrode and the movable electrode have substantially the same structure.
The arc electrode portion 31 is obtained by integrating the electrode support portion made of Cu shown in Example 1 by infiltration of Cu. This one was obtained by cutting as shown in the figure. A reinforcing flat plate 40 made of nonmagnetic austenitic stainless steel was further brazed to the electrode support portion 32, and a similar flat plate was brazed to the coil electrode 33. Coil electrode 3
Numeral 3 is made of pure copper, and was brazed to the electrode rod 34 and the electrode using a brazing material having a lower melting point than the above-mentioned brazing material.

The electrode support 32 in this embodiment is made of pure copper by infiltration.
As described above, the amount varies depending on the infiltration temperature,
It is determined in consideration of required strength and electric resistance.
The electric resistance can be reduced without lowering the strength by precipitating the compound by heat treatment. In particular, in this example, after infiltrating pure copper, it was allowed to cool to 900 ° C.,
By gradually cooling from that temperature to around 700 to 800 ° C. for 3 hours and further from that temperature to around 600 to 700 ° C. for 2 hours, Cr precipitates were formed.

FIG. 10 is a perspective view showing the connection between the electrode section and the coil electrode 33 in this embodiment. When the movable-side electrode rod 34b moves in the axial direction, the movable electrode 30b electrically contacts and separates from the fixed electrode 30a, and at the same time, an arc current 49 is generated between the two electrodes to generate metal vapor.

The metal vapor adheres to the intermediate shield member 36 supported by the vacuum vessel 35 composed of an insulating cylinder, and is dispersed by the axial magnetic field of the cylindrical coil electrode 33 to extinguish the arc. The cylindrical coil electrode 33 is attached to the fixed and movable electrodes 30a and 30b, but may be provided on at least one side.

The cylindrical coil electrode 33 attached to the back of the main arc electrode 41 is constituted by a coil electrode 42 having a cylindrical portion having an opening at one end. The coil electrode 42 formed of a cylindrical portion has the arc electrode support 13 at one end and an opening at the other end. The reinforcing member 39 is made of a high-resistance member, such as Fe or stainless steel, and is disposed between the bottom surface 43 and the main arc electrode 41. The opening end surface 45 of the cylindrical portion on the main electrode side forms two protrusions 46 and 47, and the main arc electrode 41 is electrically connected to the protrusions 46 and 47. The protrusion may be formed on the main electrode. The semicircular cylindrical portion 42 between the one protruding portion 46 and the other protruding portion 47 cuts the arcuate slits 50 and 51 to form
The arc-shaped current paths 52 and 53 are formed. One end of the current paths 52 and 53, for example, the input end 54 is
6, 47, the other end, for example, the output end 55, is connected to the electrode rod 34 via the bottom surface 43. Input end 54 and output end 5
A slanted slit groove 56 is formed between the input end 54 and the output end 55 of the cylindrical portion in which 5 overlaps. One end of the inclined slit 56 communicates with one end 50 of the arc-shaped slit, and the other end is cut between the one end 57 of the arc-shaped slit and the corresponding open end face 45. Therefore, the input end 54 and the output end 55 are electrically separated by the inclined slit groove 56. The output end 55 forms a slit 58 extending to the vicinity of the rod on the bottom surface 43 to prevent eddy current due to the axial magnetic field H.

Next, when the movable electrode 30b is separated from the fixed electrode 30a and cut off, an arc current 49 is ignited between both electrodes. The arc current 49 flows from the protrusions 46 and 47 to the input end 54 and the current paths 52 and 5 as indicated by the arrows.
3 from the output end 55 to the electrode rod 3 through the bottom surface 43.
Flow to 4.

In this current path, the current flowing through the current paths 52 and 53 and the overlapping input terminal 54 and output terminal 55 is
Since one turn is formed, the axial magnetic field H generated by the one-turn current is applied uniformly over the entire main electrode, and the arc current 49 is uniformly distributed over the entire main electrode.
The breaking performance can be improved and the entire surface of the main electrode can be used effectively, so that the vacuum circuit breaker can be downsized.

FIG. 11 is a block diagram of a vacuum circuit breaker showing the vacuum valve 59 and its operating device.

This is a small and lightweight structure in which the operation mechanism section is disposed on the front side and three sets of three-phase batch-type epoxy resin cylinders 60 having a tracking resistance, which support a vacuum valve, are disposed on the rear side.

Each phase end is of a horizontal draw-out type supported horizontally by an epoxy resin cylinder and a vacuum valve support plate. The vacuum valve is opened and closed by an operating mechanism via an insulating operating rod 61.

The operating mechanism is a simple and compact electromagnetically operated mechanical tripping free mechanism. Shock is small because the opening and closing stroke is small and the mass of the movable part is small. On the front of the main unit, in addition to the manually connected secondary terminal, an open / close indicator, operation counter, manual trip button,
A manual insertion device, a drawing device, an interlock lever, and the like are arranged.

(A) Closed state The closed state of the circuit breaker is shown, and current flows through the upper terminal 62, the main electrode 30, the current collector 63, and the lower terminal 64. The contact force between the main electrodes is determined by the contact spring 6 attached to the insulating operation rod 61.
5 is kept.

The electromagnetic force due to the contact force of the main electrode, the force of the quick-release spring, and the short-circuit current is applied to the support lever 66 and the prop 6
7 is held. When the closing coil is excited, the plunger 68 pushes up the roller 70 via the knocking rod 69 from the open state, turns the main lever 71 to close the contact, and holds it with the support lever 66.

(B) Free trip state The movable main electrode is moved downward by the separating operation, and an arc is generated from the moment the fixed and movable main electrodes are separated.

The arc is extinguished in a short time due to the high dielectric strength in vacuum and the strong diffusion action.

When the trip coil 72 is excited, the trip lever 73 disengages the prop 67 and the main lever 71 rotates by the force of the quick-release spring to open the main electrode.
This operation is a mechanical trip-free mode that is performed irrespective of the presence or absence of the closing operation.

(C) Open circuit state After the main electrode is opened, the link is returned by the reset spring 74, and at the same time, the prop 67 is engaged. When the closing coil 75 is excited in this state, the closed state shown in FIG. 76 is an exhaust pipe.

The vacuum circuit breaker cuts off the arc in a high vacuum, and has excellent breaking performance due to the high dielectric strength of the vacuum and the high-speed diffusion of the arc, but has no load on the motor and transformer. When the switch is opened and closed, the current is cut off before reaching the zero point, so that a so-called cut-off current is generated, and a switching surge voltage proportional to the product of this current and the surge impedance may be generated. For this reason, 3kV transformers and 3k
When a V, 6 kV rotating machine or the like is directly opened and closed by a vacuum circuit breaker, it is necessary to connect a surge absorber to a circuit to suppress a surge voltage and protect the equipment. As the surge absorber, a capacitor is used as a standard, but a ZnO nonlinear resistor can be used depending on the withstand voltage of the shock wave of the load.

According to the present embodiment described above, a breaking of 7.2 kV and 31.5 kA is possible at a pressure of 150 kg and a breaking speed of 0.93 m / sec.

Fifth Embodiment FIG. 12 is a diagram showing a main circuit configuration for interrupting a DC circuit by using the same vacuum valve as the fourth embodiment. 80 is a DC power supply,
81 is a DC load, 82 is a vacuum valve, 83 is a short ring, 84 is an electromagnetic repulsion coil, 85 is a commutation capacitor,
86 is a commutation reactor, 87 is a trigger gap, 88 is a static overcurrent trip device, and 89 is a ZnO nonlinear resistor.

In the present embodiment, the following features are obtained.

(1) Since no air arc is generated at the time of interruption, no noise is generated and the disaster prevention effect is large.

(2) Since the opening time is short (about 1 ms), it is possible to cut off the fault current having a rush rate exceeding the standard value, and it is possible to keep the current limiting value small.

(3) The use of a vacuum valve makes it possible to cut off the high-frequency capacitor discharge current, make the arc time extremely short (about 0.5 ms), and reduce contact wear.

(4) The current scale can be set with high accuracy by adopting a static overcurrent trip device, and there is no aging.

(5) The use of a latch-type electric spring actuator significantly reduces the operating current and eliminates the need for a holding current.

(6) The occupied area is reduced to about 1/4, and the substation space can be reduced.

Embodiment 6 FIG. 13 is a sectional view showing another electrode structure. (A) is a front view, (b) is a front view of AA part of (a).

In this embodiment, as in the first embodiment, the main electrode 92
Is infiltrated with pure copper into an arc electrode on the surface made of a Cu—Cu porous sintered body to form an electrode support. A vertical magnetic field generating coil electrode 91 is brazed to the main electrode 92. The reinforcing member 9 is made of pure iron or stainless steel.
6. Reinforced by brazing. 90 is a conductive rod.
The main electrode 92 is brazed at the convex portion 95 of the coil electrode 91.

Embodiment 7 FIG. 14 is a view showing an electrode structure of another example. (A) is a plan view and (b) is a BB sectional view of (a).

When viewed from the facing surface, the electrodes overlap each other, and are right-handed and left-handed spiral electrodes, respectively.
Numeral 100 is a member which can contact and separate from each other and is called a contact portion of the arc electrode portion. 101 is an arc runner. The spiral groove 102 has an end at the contact portion 100 and separates the arc runner 101 from each other. Each arc runner is in contact with the outer periphery of the electrode at its tip 103. In addition,
The number of arcrunners is arbitrary. The electrode is, for example, C
The arc electrode 104 and the electrode supporting portion 105 are made of a u-Cr (copper-chromium) alloy in an integrated form formed by infiltrating copper. The groove 102 can be formed by machining.

Although not shown, the electrodes of the vacuum circuit breaker having a short-circuit current of 12.5 kA or less have a simple, so-called flat plate structure without the spiral groove 102. In a flat plate structure, a contact portion, a tapered portion corresponding to an arc runner,
And an electrode periphery, which are made in one piece.

The main electrode is connected to an electrode terminal outside the vacuum vessel through a brazed electrode rod.

The operation when the short-circuit current of 12.5 to 50 kA of the AC circuit is cut off by the spiral electrode shown in FIG. 14 will be described. First, when the pair of electrodes starts opening, an arc is emitted from the contact portion 100 of the main electrode. With the lapse of time from the opening point, the arc between the electrodes is moved from the contact portion 100 to the arc runner 1.
After moving through 01, it moves to the arc runner tip 103. At this time, a radial magnetic field is formed in the electrode space due to the characteristics of the spiral electrode structure, and the direction of the magnetic field is perpendicular to the direction of the arc, so this magnetic field is called a transverse magnetic field. The movement of the arc on the electrode is promoted by the driving effect by the transverse magnetic field, and uneven consumption of the electrode is prevented.

[0104]

According to the present invention, there is provided a vacuum circuit breaker having a fixed-side electrode and a movable-side electrode having an arc electrode, a support member for supporting the arc electrode, and a coil electrode connected to the support member. The arc electrode and the arc electrode supporting member, preferably a coil electrode material, have a non-bonded and melt-integrated structure, and the supporting member and the coil electrode are 0.01 to 2.5% by weight of Cr and Ag. , V, Nb, Zr,
Since it is composed of a Cu alloy containing Si, W, Be, etc., it is possible to reduce the machining process and the assembling process of each member involved in the brazing and prevent the electrode material from being broken or dropped due to poor brazing. By improving the strength of the arc electrode supporting member and the coil electrode material, it is possible to prevent a welding failure due to electrode deformation, so that a highly reliable and safe vacuum circuit breaker, and a vacuum valve and an electric contact used therefor can be provided.

[Brief description of the drawings]

FIG. 1 is a process chart showing a method for manufacturing an electric contact of the present invention.

FIG. 2 is a sectional view of a mold when three electrical contacts are manufactured at one time.

FIG. 3 is a cross-sectional view showing the relationship between the shape of various electrodes and its production mold.

FIG. 4 is a diagram showing the relationship between the amount of solid solution of Cr and the infiltration temperature.

FIG. 5 is a diagram showing the relationship between 0.2% proof stress and the amount of solid solution of alloying elements.

FIG. 6 is a diagram showing the relationship between 0.2% proof stress and specific resistance.

FIG. 7 is a diagram showing a relationship between specific resistance and alloying elements.

FIG. 8 is a sectional view of a vacuum valve.

FIG. 9 is a sectional view of a vacuum valve electrode.

FIG. 10 is a perspective view of a vacuum valve electrode.

FIG. 11 is an overall configuration diagram of a vacuum circuit breaker.

FIG. 12 is a circuit diagram using a DC vacuum circuit breaker.

FIG. 13 is a cross-sectional view and a front view showing the structure of another example of the electrode for a vacuum valve.

FIG. 14 is a front view and a cross-sectional view of another example of an electrode for a vacuum valve.

[Explanation of symbols]

1, 12, 31a, 31b, 41, 92, 104 ... arc electrodes, 2, 13, 32a, 32b, 48, 94, 10
5: Arc electrode support, 4, 9: alumina powder, 5: graphite container, 6: porous sintered body, 7: infiltration material, 8: feeder, 1
4, 33a, 33b, 42, 91 ... coil electrode, 15,
22, 34, 34a, 34b, 90, 106 ... electrode rods,
17, 27, 44, 96 ... reinforcing member, 35 ... vacuum vessel,
36: shield member, 37: bellows, 56: slit groove, 60: epoxy resin cylinder, 61: insulating operation rod,
62: upper terminal, 63: current collector, 64: lower terminal, 65
... contact spring, 66 ... support lever, 68 ... plunger, 7
DESCRIPTION OF SYMBOLS 1 ... Main lever, 72 ... Release coil, 75 ... Making coil, 76 ... Exhaust cylinder, 80 ... DC power supply, 81 ... DC load, 82 ... Vacuum valve, 83 ... Short ring, 84 ...
Electromagnetic repulsion coil, 85: commutation capacitor, 86: commutation reactor, 87: trigger gap, 88: static overcurrent trip device, 89: ZnO nonlinear resistor.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yukio Kurosawa 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Yoshio Koguchi 1-chome Kokubuncho, Hitachi City, Ibaraki Prefecture No. 1-1 Inside the Kokubu Plant, Hitachi, Ltd. (72) Inventor Toru Tanimizu 1-1-1, Kokubuncho, Hitachi City, Ibaraki Prefecture Inside the Kokubu Plant, Hitachi, Ltd. (72) Yoshimi Hakamada Kokubuncho, Hitachi City, Ibaraki Prefecture 1-1-1, Kokubu Plant, Hitachi, Ltd. (72) Inventor, Toshiyoshi Endo 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture F-term, Hitachi Research Laboratory, Hitachi, Ltd. F-term (reference) 5G023 AA02 BA13 CA21 CA35 5G026 BA01 BA04 BB02 BB03 BB04 BB08 BB10 BB12 BB14 BB15 BB16 BB17 BB18 BC02 CA01 CB02 DA02 DB05 5G027 AA03 AA13 BA02 BB01

Claims (11)

[Claims] 1. A vacuum valve having a fixed side electrode and a movable side electrode in an insulating container, and a conductor connected to each of the fixed side electrode and the movable side electrode inside the vacuum valve outside the vacuum valve. In a vacuum circuit breaker comprising a terminal and opening / closing means for driving the movable-side electrode via an insulating rod connected to the movable-side electrode, the fixed-side electrode and the movable-side electrode are made of a refractory metal and a highly conductive metal. An arc electrode made of an alloy with a metal, and an electrode support portion made of a highly conductive metal that supports the arc electrode, wherein the arc electrode and the electrode support portion are integrally formed by melting the highly conductive metal. A vacuum circuit breaker characterized in that at least one of the fixed side electrode and the movable side electrode is provided with a vertical magnetic field generating coil made of a highly conductive metal on the electrode support portion. 2. The arc electrode is made of a composite alloy of a highly conductive metal impregnated in a porous refractory metal. The vacuum circuit breaker according to claim 1, wherein the vacuum circuit breaker is formed. 3. The vacuum circuit breaker according to claim 1, wherein the vertical magnetic field generating coil has a cylindrical shape and a slit groove formed in a circumferential surface thereof, or a cross section thereof is substantially swastika. 4. A vacuum valve having a fixed side electrode and a movable side electrode in an insulating container, and a conductor connected to each of the fixed side electrode and the movable side electrode inside the vacuum valve outside the vacuum valve. In a vacuum circuit breaker comprising a terminal and opening / closing means for driving the movable-side electrode via an insulating rod connected to the movable-side electrode, the fixed-side electrode and the movable-side electrode are made of a refractory metal and a highly conductive metal. An arc electrode made of an alloy with a metal, and an electrode support portion made of a highly conductive metal that supports the arc electrode, the arc electrode and the electrode support portion are integrally formed by the highly conductive metal, 0.2% proof stress of the electrode support part is 10 kg / mm ² or more and specific resistance is 2.8 μΩ
cm or less, and at least one of the fixed side electrode and the movable side electrode is provided with a vertical magnetic field generating coil made of a highly conductive metal on the electrode support portion. 5. A vacuum valve having a fixed side electrode and a movable side electrode in an insulating container maintained in a high vacuum, wherein both electrodes are arc electrodes made of a composite member of a refractory metal and a highly conductive metal. And an electrode support portion made of a highly conductive metal that supports the arc electrode, and a vertical magnetic field generating coil connected to the electrode support portion, wherein the arc electrode and the electrode support portion are the highly conductive metal. A vacuum valve, wherein the vacuum valve is formed integrally by melting. 6. A vacuum valve having a fixed side electrode and a movable side electrode in an insulating container maintained in a high vacuum, wherein both electrodes are arc electrodes made of a composite member of a refractory metal and a highly conductive metal. And an electrode support made of a highly conductive metal supporting the arc electrode, and a vertical magnetic field generating coil connected to the electrode support, wherein the arc electrode, the electrode support and the magnetic field generating coil are A vacuum valve, which is integrally formed of a highly conductive metal, wherein the electrode support has a 0.2% proof stress of 10 kg / mm ² or more and a specific resistance of 2.8 μΩcm or less. 7. An arc electrode made of an alloy of a refractory metal and a highly conductive metal, an electrode support made of a highly conductive metal for supporting the arc electrode, and a longitudinal magnetic field connected to the electrode support. An electrical contact, wherein the coil and the coil are formed integrally by melting the highly conductive metal. 8. An arc electrode made of an alloy of a refractory metal and a highly conductive metal, an electrode support made of a highly conductive metal for supporting the arc electrode, and a longitudinal magnetic field connected to the electrode support. An electrical contact, wherein a coil is integrally formed of the highly conductive metal, and the electrode support has a 0.2% proof stress of 10 kg / mm ² or more and a specific resistance of 2.8 μΩcm or less. 9. An arc electrode made of an alloy of a refractory metal and a highly conductive metal, an electrode support made of a highly conductive metal for supporting the arc electrode, and a longitudinal magnetic field connected to the electrode support. In the method of manufacturing an electrical contact having a coil, the arc electrode comprises placing the highly conductive metal on a porous sintered body having a refractory metal, melting the highly conductive metal, and melting the porous body. The electrode support and the magnetic field generating coil are formed by setting the thickness of the highly conductive metal remaining after the infiltration to a thickness required for the electrode support. A method for producing an electrical contact, comprising: 10. The arc electrode, the electrode support, and the magnetic field generating coil are formed by infiltrating and solidifying the highly conductive metal, and then maintained at a desired temperature to be supersaturated in the highly conductive metal. The method for producing an electrical contact according to claim 8, further comprising a heat treatment step of precipitating a dissolved metal or an intermetallic compound. 11. The method according to claim 9, wherein the thickness and shape of the highly conductive metal remaining after infiltration into the porous body are formed by melting and solidifying according to the shapes of the electrode support and the vertical magnetic field generating coil. The method for producing an electrical contact according to any one of the above.