JPH0693340B2 - Vacuum interrupter electrode material - Google Patents

Description

The present invention relates to a vacuum interrupter electrode material.

B. Outline of the Invention The present invention relates to a vacuum interrupter electrode material formed of an alloy composed of copper, molybdenum and chromium, wherein the electrode material is 55 to 80% by weight of copper and 15 to 35% by weight of molybdenum.
And chromium 4 to 12% by weight, and by limiting the particle size of the molybdenum and chromium powders, the probability of flashover (re-ignition, re-ignition) is extremely low, and frequent opening and closing is possible. It is the most suitable for opening and closing capacitors.

C. Conventional technology Generally, the electrode material of a vacuum interrupter has a high ability to cut or cut a large current, a high dielectric strength, a good welding resistance, a small current can be cut or cut, etc. Is required to be satisfied.

Conventionally, as one satisfying the above conditions, for example, Japanese Patent Laid-Open No.
The electrode material disclosed in Japanese Patent No. 27418 is known.
The electrode material of such a vacuum interrupter is obtained by sintering powders of molybdenum Mo and chromium Cr having the same grain size of 149 μm or less (-100 mesh) to form a sintered body, and infiltrating copper Cu into the sintered body. The alloy is composed of 20 to 70 wt% Cu, 10 to 70 wt% Mo and 10 to 70 wt% Cr.

D. Problems to be Solved by the Invention The electrode material of the conventional vacuum interrupter described above has excellent breaking and breaking performance, is particularly excellent in breaking and breaking a large current due to an accident, and exhibits high withstand voltage characteristics.

However, when a capacitor was opened and closed using the electrode material of this vacuum interrupter, reignition occurred.
In the case of opening and closing the capacitor, unlike normal switching, a voltage twice as high as the system voltage is applied between the electrodes at the time of opening, and an instantaneous large current (rush current) of about 5 times as much as the system current flows when the capacitor is turned on. For this reason, when the capacitor is frequently opened and closed, re-ignition and re-ignition are likely to occur, so that the circuit may be destroyed unless the opening and closing is performed reliably.

In order to prevent re-ignition and re-ignition, it is necessary to eliminate unstable elements such as oxides, gas impurities and pinholes in the electrode material.

By the way, Cu-Mo-Cr alloy porous substrate (skeleton)
In the Mo-Cr sintered body as described below, Cr is easily oxidized and a passivation film is easily formed on the surface of Cr particles. Therefore, when the amount of Cr is large, the leaking property of Cu deteriorates due to the presence of the passivation film on the surface of the Cr particles, and voids and infiltration defects are generated, and the tendency to form pinholes becomes remarkable. Re-ignition and re-ignition phenomena are likely to occur. On the other hand, if the amount of Cr is reduced, the amount of Mo must be increased, but since Mo tends to emit thermoelectrons, use of too much Mo leads to deterioration in withstand voltage characteristics. I will end up.

Then, the inventor paid attention to the fact that in the above-mentioned conventional Cu-Mo-Cr alloy, both the maximum particle diameters of Mo and Cr powders before the alloy production were 149 µm (-100 mesh),
By making the maximum particle diameters of Mo and Cr powders different from each other, diffusion bonding between them can be surely performed, and in the Mo-Cr sintered body, it is possible to reduce the proportion of each particle of Mo and Cr existing independently. It was. Because each of Mo and Cr particles (including particles of Mo powder and particles of Cr powder that are combined and growing) is present independently, and if an arc spot is directly formed on that particle, the particles of Mo and Cr This is because each of these drawbacks will appear prominently.

E. Means for Solving Problems In order to solve the above-mentioned conventional problems, the present invention provides an electrode material for a vacuum interrupter in which the voids of a porous base material composed of Mo powder and Cr powder are filled with copper. In, the alloy consists of 55-80% by weight of Cu, 15-35% by weight of Mo and 4-12% by weight of Cr, the grain size of Cr before alloy production is 149 μm or less, and the maximum grain size of Mo is 1 / the maximum grain size of Cr. It is set to 2 or less.

If the Cu content is less than 55% by weight, the electrical conductivity will decrease and the contact resistance will increase, and if it exceeds 80% by weight, the welding resistance will deteriorate. Further, when Mo is less than 15% by weight, the welding resistance is deteriorated, and when it exceeds 35% by weight, the probability of flashover becomes high and the current-carrying ability and the disconnecting ability are deteriorated. Further, when Cr is less than 4% by weight, the probability of re-ignition increases and the welding resistance deteriorates, and when it exceeds 12% by weight, the probability of flashover increases.

F. Action In the electrode material of the vacuum interrupter having such a configuration,
Since the grain size of Mo is smaller than that of Cr and the amount of Mo is larger than that of Cr, Mo and Cr are sufficiently diffusion-bonded to form a sintered body of a porous substrate. It is considered that the arc spots cannot be directly formed on the particles of Mo or Cr because the proportions of Mo, Cr and Cr present respectively are extremely small. Further, since the amount of Cr is small, it is considered that the adverse effect of the passivation film on the surface of the Cr particles is eliminated, and further, a part thereof is released and removed when diffusion-bonding with Mo, and the adverse effect of the passivation film is further eliminated. Therefore, according to the electrode material of the vacuum interrupter of the present invention, the occurrence rate of flashover (re-ignition, re-arcing) is extremely reduced, and stable frequent opening and closing is performed.

G. Example Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

A vacuum interrupter using the electrode material according to the present invention is, for example, as shown in FIG. 3, positioned in the vacuum container 1 on its axis so that a pair of electrode rods 2, 2 can be relatively moved toward and away from each other. Introduced, the electrodes 3, 3 forming a pair are fixed to the inner end portion of each electrode rod 2 with an insulating spacer interposed, and each electrode rod 2 and electrode 3 is fixed.
Are generated on the back side of the electrode 3 and change the axial current (vertical direction in FIG. 3) flowing through the electrode rod 2 into a loop current centered on the electrode rod 2 to generate a longitudinal magnetic field. The coils 4 and 4 as members are connected to each other to have a schematic structure.

That is, the vacuum container 1 is made of Fe-N in which two cylindrical insulating cylinders 5 made of glass or ceramics are fixed at both ends.
Thin-walled ring-shaped sealing metal fittings 6, 6 made of i-Co alloy or Fe-Ni alloy, etc. are joined together to form one insulating cylinder, and both open ends of the other sealing metal fittings. It is formed by closing the disc-shaped metal end plates 7 and 7 via 6 and 6, and evacuating the inside to a high vacuum (for example, a pressure of 6.665 mPa or less). Then, the electrode rods 2 are introduced into the vacuum container 1 from the center of the respective metal end plates 7 so as to be relatively close to and away from each other while maintaining the airtightness of the vacuum container 1.

One of the electrode rods 2 (upper side in FIG. 3) is airtightly attached to one of the metal end plates 7, and the other electrode rod 2 of the vacuum container 1 has a metal bellows 8 interposed therebetween. The other metal end plate 7 is inserted movably in the axial direction while maintaining airtightness. In FIG. 3, 9 and 10 are shaft shields and bellows shields, 11 is a main shield, and 12 is an auxiliary shield.

As shown in FIGS. 1 and 2, the inner end portion of each electrode rod 2 is made of a material having high conductivity such as Cu, and
Disc-shaped mounting base 4a with a diameter appropriately larger than the diameter of the electrode rod 2
And two arms 4b extending outward in the radial direction (left-right direction in FIG. 1) from opposite positions on the outer circumference of the mounting base 4a, and in the same direction from the end of each arm 4b about the mounting base 4a. 1/2 consisting of a circular arc part 4c curved in a circular arc shape
The shunt type coil 4 is fixed by brazing via a recess 13 formed on one surface (downward in FIG. 1) of the mounting base 4a.

The coil 4 includes a ring-shaped mounting portion 14a fitted to the outer periphery of the inner end of the electrode rod 2 by brazing, and a plurality of support arms 14b radially extending outward from the outer periphery of the mounting portion 14a.
And a ring-shaped support portion 14c that connects the ends of the support arms 14b.
And a coil reinforcing member 14 made of and are brazed and reinforced.

The coil reinforcement 14 is made of a material having high mechanical strength and low electrical conductivity such as stainless steel.

A circular recess 15 is provided on the other surface of the mounting base 4a of the coil 4, and the recess 15 is made of a material such as stainless steel or Inconel having high mechanical strength and low conductivity. The insulating spacer 16 formed in a cylindrical shape,
It is fixed by brazing via a small diameter flange 16a formed at one end thereof. Then, the large-diameter flange 16b formed on the other end of the insulating spacer 16 is mounted in the shape of a circular plate having a through hole having a diameter substantially larger than that of the large-diameter flange 16b and having a diameter substantially equal to the inner diameter of the insulating spacer 16. Base 17a and mounting base 1
2 extending outward in the radial direction from opposite positions on the outer circumference of 7a
From the arm 17b of the book and the arc portion 17c which has a radius of curvature substantially equal to that of the arc portion 4c of the coil 4 from the end of each arm 17b and which is curved in an arc shape with an appropriate length in the same direction opposite to this. The auxiliary coil 17 made of a material having high conductivity such as copper is fixed by brazing via the engaging step portion 18 provided on one surface (downward in FIG. 2) of the mounting base 17a. . The auxiliary coil 17 and the coil 4 have one end fixed to a recess 19 provided at the end of each arc portion 17c of the auxiliary coil 17, and the other end provided at the end of each arc portion 4c of the coil 4. It is electrically connected via an axial current-carrying pin 20 inserted into the through hole 21.

The diameter of the auxiliary coil 17 is approximately the same as the diameter of the coil 4 (outer diameter 80
mm) electrode 3 has a recess 21 formed in the center of the back surface thereof.
It is joined to the mounting base 17a by brazing via each of the arms, and each arm 17b and the arc portion 1 are also brazed via the back surface.
It is joined with 7c. The facing surface of the electrode 3 is 60% by weight of Cu,
It is formed of a disc-shaped thin plate 22 made of an alloy of Mo 30% by weight and Cr 10% by weight. The outer diameter of the thin plate 22 is 30 mm in the center.
Is provided with a contact portion 23 protruding in a disk shape and capable of coming into contact with and separating from the counter electrode, and a portion having a diameter larger than the contact portion 23 serves as an arc diffusion portion 24. In this embodiment, the contact portion 23 has a thickness of 2 mm and the arc diffusion portion 24 has a thickness of 1 mm.

On the other hand, the back surface portion 25, which is a portion other than the facing surface of the electrode 3 (other than the thin plate 22), has a conductivity (IACS%) of 7% of 40Cu-20Cr-40.
It is made of Fe. The thin plate 22 and the back surface part 25 are joined by brazing or the back surface part 25 is joined at the same time when Cu of the thin plate 22 is infiltrated.

In order to manufacture the electrode material for forming the thin plate 22 of the electrode 3, a predetermined amount of Mo powder having a maximum particle size of 74 μm or less and an average particle size of 3 μm and Cr powder having a particle size of 149 μm or less (-100 mesh) are machined. The mixed powder is stored in an alumina container, and a Cu block is placed on the mixed powder. Then, these are heated at 1000 ° C. for 10 minutes in a vacuum furnace maintained at a pressure of 6.67 mPa or less to form a Mo—Cr sintered body (porous substrate). Next, the vacuum furnace is heated to 1150 ° C., heated for 10 minutes, and then cooled and solidified in the furnace to manufacture an electrode material.

The vacuum interrupter having the above configuration was incorporated in a circuit as a capacitor opening / closing, and the flashover probability was investigated. The test method is 66kV-60
It is set to be equivalent to the switching condition of the MVA capacitor capacity. The conditions for making the DC voltage are 54kVr.ms to the capacitor in advance.
Was charged, and a current of 3700 A peak and 200 cycles was applied by LC vibration. On the other hand, the power supply voltage of 50 cycles is 50kV.
rms, current of 520A was set as the advance current, and turning on and off was repeated many times under this condition. The gap between the poles is 15 mm, the closing speed is 1 m / sec, and the breaking speed is 2 m / sec.
The results are shown in the following table and FIG.

For comparison, as an electrode material for forming the thin plate 22 of the electrode 3, for example, Mo powder and Cr powder each have a particle size of 149 μm or less (−100 mesh) or the like, and Cu 60 wt%, M
With respect to the vacuum interrupter using an alloy composed of 30 wt% and 10 wt% Cr, the flashover probability was examined under the same test conditions as those of the above-mentioned examples, and the results are shown in the following table and FIG.

The above table shows that when the number of test opening and closing is 350 times, Mo and Cr
Each particle size of the powder is 149μm or less (-100 mesh)
This is a comparison when the number of flashovers is 100%. Further, in the table, Mo particles having an average particle diameter of 1 to 10 μm all satisfy the condition that they are 1/2 or less of the maximum particle diameter of Cr.

On the other hand, in FIG. 4, the horizontal axis represents the number of test opening / closing operations (times) and the vertical axis represents the cumulative number of flashover occurrences (times). In FIG. 4, the solid line 26 shows the change in the number of flashovers according to the above-mentioned embodiment, and the broken line 27 shows the change in the flashover counts when the particle diameters of Mo and Cr powders were each smaller than 149 μm (-100 mesh). Shows.

As can be seen from the above table and FIG. 4, when the Mo powder particle size is 74 μm or less (−200 mesh) at the maximum and the Cr powder particle size is 149 μm or less (−100 mesh) at the maximum, the number of occurrences of flashover occurs. It is suitable for opening and closing capacitors because it can open and close frequently and stably. this is,
This is probably because diffusion bonding between Mo and Cr is sufficiently performed. Further, particularly, those having an average particle size of Mo of 1 to 10 μm and a maximum particle size of 1/2 or less of Cr are good.

In addition, Cu is 55-80 wt%, Mo is 15-35 wt% and Cr
It has been experimentally found that similar results can be obtained in the range of 4 to 12% by weight.

H. Effect of the Invention As described above, according to the electrode material of the vacuum interrupter of the present invention, the component composition range of the Cu-Mo-Cr alloy is limited, and the particle sizes of Mo and Cr powders are specified differently. Since Mo and Cr are sufficiently diffusion-bonded, the probability of re-ignition is extremely low, stable and frequent switching can be performed, and it is ideal as an electrode material for a vacuum interrupter for switching capacitors. Is.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view of an electrode using an electrode material of a vacuum interrupter of the present invention, and FIG. 2 is a partially exploded perspective view of FIG.
FIG. 3 is a vertical sectional front view of a vacuum interrupter provided with the electrodes shown in FIG. 1, and FIG. 4 is a graph showing the number of cumulative flashover occurrences. 3 ... Electrode, 22 ... Thin plate, 23 ... Contact part, 24 ... Arc diffusion part,
25 ... Rear part.

Claims (2)

[Claims] 1. A vacuum interrupter electrode material comprising a porous substrate composed of molybdenum powder and chromium powder filled with voids with copper.
% Vacuum and 4-12% by weight of chromium, vacuum characterized in that the grain size of chromium before manufacturing the alloy was 149 μm or less and the maximum grain size of molybdenum was 1/2 or less of the maximum grain size of chromium. Electrode material for interrupter. 2. The electrode material for a vacuum interrupter according to claim 1, wherein the average particle size of molybdenum before the alloy is manufactured is 1 to 10 μm.