JP2661201B2 - Electrode materials for vacuum interrupters - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrode material for a vacuum interrupter made of an inexpensive infiltration type composite metal with improved characteristics such as current breaking performance and current breaking value.

B. Summary of the Invention An electrode material for a vacuum interrupter made of copper, chromium, cobalt, molybdenum, and bismuth, and has improved characteristics such as welding resistance, current breaking performance, and current breaking value.

C. Conventional technology In general, the main performances required as electrode materials for vacuum interrupters are (1) good welding resistance (2) high current breaking performance (3) low current breaking value And the like.

However, increasing the current breaking performance of the electrode material and lowering the current breaking value are caused by physical properties that contradict each other.Therefore, it is impossible for a single electrode material to satisfy all the properties described above. At present, it is difficult to select an electrode material that best meets the specifications of the vacuum interrupter.

For example, a copper-bismuth alloy disclosed in Japanese Patent Publication No. 41-12131 is obtained by adding 0.5% by weight of bismuth (Bi) having a high vapor pressure and a low melting point to copper (Cu), and has a high resistance to welding and electric current. It is well known that the breaking performance is good.
The tungsten copper sintered metal disclosed in Japanese Patent Publication No. 54-36121 is obtained by adding 20% by weight of copper to tungsten (W) having a low vapor pressure and a high melting point, and has a low current breaking value. Has advantages. As an electrode material having a particularly low current interruption value, a silver-silver tungsten sintered metal disclosed in Japanese Utility Model Application Laid-Open No. 55-121429, that is, tungsten carbide (WC) was added with 30% by weight of silver (Ag). There are things.

D. Problems to be Solved by the Invention Copper-bismuth alloy has good current breaking performance,
The current interruption value is as high as 10 A, for example, and an interruption surge may occur when the current is interrupted. For this reason, it is difficult to satisfactorily cut off the small delay current, and there is a possibility that the electric equipment on the load side may be broken down.

Further, although the sintered copper tungsten metal and the sintered silver silver tungsten metal have low current breaking values, they have poor current breaking performance and cannot break large currents such as short-circuit currents. Furthermore, since the tungsten silver carbide sintered metal contains a relatively large amount of silver, it is expensive as an electrode material, which is an obstacle to reducing the unit cost of manufacturing a vacuum interrupter.

E. Means for Solving the Problems The electrode material of the vacuum interrupter according to the present invention comprises copper in the range of 20 to 70% by weight to improve properties such as welding resistance, current breaking performance and current breaking value. Chromium in the range of 2 to 75% by weight; cobalt in the range of 0.1 to 10% by weight; molybdenum in the range of 2 to 75% by weight;
Of bismuth in the range of weight percent.

In this case, the chromium powder, the cobalt powder, and the molybdenum powder are uniformly mixed and heated at a temperature equal to or lower than the melting point of cobalt (and chromium and molybdenum) to obtain a porous sintered body. Copper and bismuth are infiltrated into the voids of the sintered body to obtain the electrode material of the present invention. The sintering and infiltration steps are desirably performed while degassing in a non-oxidizing atmosphere.

Here, when the copper content is less than 20% by weight, the electric conductivity decreases and the calorific value increases. Conversely, when the copper content exceeds 70% by weight,
This results in a decrease in welding resistance and an increase in current breaking value. When the chromium content is less than 2% by weight, the molybdenum content is less than 2% by weight, or the bismuth content is less than 1% by weight, the current breakage value increases. In addition, chrome
If the content exceeds 75% by weight or the content of molybdenum exceeds 75% by weight, the current interrupting performance decreases.
On the other hand, when the content of cobalt exceeds 10% by weight, the reaction with copper proceeds to bring about a decrease in electric conductivity.
When the amount is less than the weight%, the withstand voltage characteristics are deteriorated.
On the other hand, when bismuth exceeds 20% by weight, the durability as an electrode and a vacuum interrupter rapidly decreases.

F. Action Since the optimum composition of copper, chromium, cobalt, molybdenum, and bismuth was found, the characteristics required for vacuum interrupters such as welding resistance, dielectric strength, current breaking performance, and current breaking value were improved as a whole. The obtained electrode material is obtained.

G. Embodiment The vacuum interrupter has a second structure representing an example of its schematic structure.
As shown in the figure, electrodes 13 and 14 are integrally provided on opposing end surfaces of a pair of lead rods 11 and 12 which are directly formed with each other. The center of the outer periphery of the cylindrical shield 15 surrounding the electrodes 13 and 14 is held in a state sandwiched between a pair of insulating cylinders 16 and 17 surrounding the shield 15. One of the lead rods 11 hermetically penetrates a metal end plate 18 joined to one end of one insulating cylinder 16, and
It is fixed integrally to. The other lead rod 12 connected to a driving device (not shown) is connected via a bellows 20 to the other metal end plate 19 airtightly joined to the other end of the other insulating cylinder 17, and is associated with the operation of the driving device. The movable electrode 14 opens and closes with respect to the fixed electrode 13 so that the movable electrode 14 can reciprocate in the direction opposite to the electrodes 13 and 14.

The electrodes 13, 14 are made of copper (Cu) in the range of 20 to 70% by weight.
Chromium (Cr) in the range of 2 to 75% by weight;
It is composed of a composite metal comprising cobalt (Co) in the range of 0% by weight, molybdenum (Mo) in the range of 2 to 75% by weight, and bismuth (Bi) in the range of 1 to 20% by weight.

An example of a method for producing this electrode material is described below.
Chromium, cobalt, and molybdenum powders having a particle size of 100 mesh were mechanically mixed, a predetermined amount of the mixed powder was charged into a container made of alumina ceramic, and a lump of copper-bismuth alloy was placed on the mixed powder. In this state, the vessel is covered with a lid, and these are heated in a vacuum furnace while being degassed. First, chromium particles, cobalt particles, and molybdenum particles are diffusion-bonded to obtain a porous infiltration base material. Thereafter, copper and bismuth are infiltrated into the voids of the infiltration base material,
At this time, the interior of the container becomes an atmosphere containing a large amount of bismuth vapor. Then, the obtained electrode material is taken out of the container and machined into a predetermined shape.

In this way, an electrode material consisting of Cr: 7% by weight, Co: 3% by weight, Mo: 30% by weight, Bi: 15% by weight, and Cu: remainder was prepared as a first sample, and in addition to this first sample, Cr: 20% % By weight Co: 5% by weight Mo: 20% by weight Bi: 12% by weight Cu: remaining second sample and Cr: 30% by weight Co: 1% by weight Mo: 7% by weight Bi: 15% by weight Cu: remaining Prepare third samples, each having a diameter of 50 mm and a thickness of 50 mm.
Processed into a 6.5 mm disk shape and rounded with a radius of curvature of 4 mm on the outer periphery and incorporated as electrodes 13 and 14 of the vacuum interrupter shown in FIG. 7, welding resistance, current breaking performance and current breaking The value was checked.

Regarding the welding resistance, the movable electrode 13 is fixed to the fixed electrode.
Pressurized at 130kgf against 14, 25kA (rms) in this state
After applying the current for 3 seconds, a static tensile force of 200 kgf was applied to the electrode 13, and the electrode 13 could be separated from the electrode 14 without any problem in all three samples. The subsequent increase in contact resistance was within 20% for all three samples.

Regarding the current breaking performance, a current of 20 kA (rms) can be cut off for the first sample, a current of 23 kA (rms) can be cut off for the second sample, and a current of 26 kA (rms) for the third sample under the voltage condition of 7.2 kV. ) Was able to cut off the current.

On the other hand, regarding the current interruption value, the vacuum interrupter was switched on and off at 200 V and 120 A, and after 100 times, 1000 times, 10,000 times,
As a result of calculating the current break values after 100,000 times, as shown in FIG. 1, good results were obtained, which were within about 1 A even after 100,000 times. The circles, triangles, and crosses shown in FIG. 1 represent the average values of 50 measurements, respectively. ... × indicate the transition of each current break value of the third sample.

H. Effect of the Invention According to the electrode material of the vacuum interrupter of the present invention, copper in the range of 20 to 70% by weight, chromium in the range of 2 to 75% by weight, cobalt in the range of 0.1 to 10% by weight, From75
It is composed of molybdenum in the range of 1% by weight and bismuth in the range of 1 to 20% by weight. It is possible to obtain an electrode material having a higher current breaking performance than a binding metal, and having generally improved properties such as welding resistance, current breaking performance, and a current breaking value. Specifically, even after 100,000 switching operations,
It is possible to provide a vacuum interrupter which can be maintained at a low value. Further, since no expensive silver is used, the cost of the electrode material itself can be reduced.

[Brief description of the drawings]

FIG. 1 is a graph showing the characteristics of a current interruption value when the present invention is applied to a vacuum interrupter, and FIG. 2 is a sectional view showing an example of the vacuum interrupter. In the figure, reference numerals 11 and 12 are lead rods, and 13 and 14 are electrodes.

Claims (1)

(57) [Claims] 1. A copper alloy in the range of 20 to 70% by weight, chromium in the range of 2 to 75% by weight, cobalt in the range of 0.1 to 10% by weight, molybdenum in the range of 2 to 75% by weight, From
Bismuth in the range of 20% by weight is mixed with chromium powder, cobalt powder and molybdenum powder, and heated at a temperature lower than the melting point of cobalt, chromium and molybdenum to form a porous sintered body. An electrode material for a vacuum interrupter, which is obtained by infiltrating copper and bismuth into voids of the sintered body.