JPS60193220A - Contact material for 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 [Field of the Invention] The present invention relates to improvements in Cu--Cr contacts used in vacuum circuit breakers.

[Prior art and its problems]

Generally, a vacuum breaker has the following characteristics.

1. The current is cut off in a vacuum chamber, and the ionization effect at the natural zero value of the current is due to the diffusion of electrons in a high vacuum, resulting in a significantly larger and better cutoff than those using other arc-extinguishing principles. Demonstrate performance.

2. Since the arc is not exposed when shutting off, there is no risk of fire or explosion, making it safe.

3. It can be made small and lightweight, which helps save labor in maintenance and inspection.

4. Less noise when shutting off.

5. Since the contacts are sealed in a vacuum, they are not affected by the atmosphere and do not require maintenance.

6. No special auxiliary equipment or accessories are required other than the equipment that opens and closes the contacts.

Because of the many features mentioned above, vacuum interrupters are increasingly in demand for power receiving and distribution equipment in general industries, buildings, and factories, and the scope of their use is being further expanded.

Selection of the contact material used in this vacuum interrupter is important, and contact materials are usually required to have the following characteristics.

(11) The gas must be sufficiently degassed.

(2) Good electrical and thermal conductivity.

(3) Low wear and tear and no welding.

(4) Excellent breaking performance.

(5) Low contact resistance and large current carrying capacity.

(6) High pressure resistance.

(7) The cutting current is small.

Among these, the breaking current is a characteristic phenomenon of vacuum circuit breakers, which is also a drawback.When breaking a small current, the arc cannot be maintained stably before the current reaches its natural zero point. Due to the problem of sudden dissipation, abnormal voltage is generated in inductive circuits using vacuum breakers, deteriorating the insulation of equipment, and causing equipment damage. A small current value is required, but this characteristic is mostly determined by the contact material.

From the above, it is desired to select an appropriate material for vacuum breaker contacts that has large current breaking performance and excellent welding resistance and cutting current characteristics, but these required properties may be contradictory, so It is difficult to obtain a contact material that satisfies the above requirements, and there are many applications in which the material satisfies particularly important characteristics depending on the application, while sacrificing some other characteristics.

For example, Cu-B1 alloys and Cu-Cr alloys are well known as typical contact materials of this type that have been used in the past.Among these, Cu-Bi alloys have excellent breaking performance and welding resistance. Although the Bi contained in this alloy tends to deteriorate the withstand voltage characteristics of the interrupter in a vacuum, and the interrupter has a low interrupting current value, it repeatedly interrupts large currents. As a result, the leaching and evaporation of Bi becomes more active, resulting in the deterioration of the cutting current characteristics. On the other hand, Cu-C
In r-based alloys, Cu and Cr are originally difficult to melt together, so C
It is obtained by infiltrating molten Cu into a sintered body of r powder, and the proportion of Cr in this alloy is usually 20 to 60% by weight. This Cu-Cr alloy chopstick breaking performance,
It is generally recognized that it is effective as a contact for vacuum circuit breakers because it has relatively excellent withstand voltage characteristics and cutting current characteristics, and Cr, which is a constituent element of this alloy, has a getter action that absorbs gas. There is. However, the Cu-Cr alloy has a disadvantage in that the welding resistance is inferior to the Cu-B1 alloy.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned points, and its object is to provide a Cu--Cr contact material for a vacuum breaker that has excellent welding resistance and cutting current characteristics.

[Key points of the invention]

The contact material of the present invention has Cu of 45 to 60 and Te of 0.0.
It is a Cu-Cr-Te alloy consisting of 5 to 4 pieces and the remainder Cr, and is obtained by infiltrating a Cu-Te alloy into a Cr sintered body.

[Embodiments of the invention]

The present invention will be explained below based on examples.

Normally, to manufacture Cu-Cr alloys, the sintering and washing method is used as mentioned above. For example, Cr powder is first filled into a graphite mold, and this is vacuum sintered at 1200 to 1350°C for several hours to sinter the Cr. This Cr sintered body was heated at 1100°C in vacuum.
Infiltrate Cu at ~1250°C. In order to obtain the alloy of the present invention, the method was basically the same as this, but a Cu--Te alloy was used instead of Cu to add Te. The reason for adding Te is that by uniformly and finely dispersing the brittle Te in the Cu-Cr alloy, welding of contacts is less likely to occur, and because Te has a higher vapor pressure than Cu or Cr, it can be used to interrupt current. This is because separate experimental results showed that it is effective to lower the cutting current value in order to sustain the arc for a long time. In the present invention, first, 1o.

Needle powder with a particle size of less than 325 Metsu and more than Metsu with an inner diameter of 657111! Finally, it was filled into a graphite mold with a depth of 25 mm while being vibrated, and vacuum sintered at 1250'0 for 1 hour to obtain a Cr sintered body with a porosity of 50 tl). Cu-0,11Te, Cu-1%Te, Cu- which had been prepared in advance by vacuum melting
Five types of Cu-Te alloys with different Te contents, 3%Te, Cu-5%Te, and Cu-8%Te, were each infiltrated at 1200''C in a vacuum atmosphere to determine the optimal content of Te. The porosity of the Cr sintered body can be adjusted to 4 by setting the sintering temperature of the Cr powder in the range of 1100 to 1400°C.
The porosity can be in the range of 5 to 55 cm, and when the five types of Cu-Te alloys mentioned above are infiltrated with the porosity in this range, Cu-C
The content of Cu in the r-alloy is also determined to be 45-60%.
becomes.

Five types of Cu-Cr-Te obtained in this way
The chemical composition and physical properties of the alloy are shown in Table 1. For comparison, Table 1 also lists conventional alloys obtained by infiltrating Cr sintered bodies with vacuum-melted Cu, but ml-1
&L5 is an alloy of the present invention, and l&16 is a conventional alloy.

Table 1 From Table 1, the physical properties of the Cu-Cr-Te alloy of the present invention can be considered to be almost the same as those of the conventional Cu-Cr alloy, although the electrical conductivity is slightly lower.

Next, from these alloys a diameter of 15 mm and a height of IQ m
A welding test piece with a tip diameter of 100R was taken, and the welding force was measured using a welding tester. The test conditions were a contact force of 8 Kf on the test piece + a vacuum level of 5 x 10 torr, and the applied current was increased in steps from 2 kA to 1 kA, and the welding force was measured up to 10 kA after energization. As shown in the figure. The first chart is a diagram showing the relationship between welding force and test current value.
The labels attached to each curve in the figure correspond to each other. Fig. 1 also plots the conventional alloy Na6, but since the alloy of the present invention has no significant difference in welding force, 1 shows the maximum welding force at a test current of 10 kA, and 4 shows the lowest welding force at a test current of 10 kA. Only three curves, 4 and -3, which represent intermediate values, are shown.
Floors 2 and 5 have been omitted because their curves tend to intersect, making it difficult to distinguish between them. Figure 1 shows that the welding force of the alloy of the present invention is significantly lower than that of conventional alloys, and even if the contacts are welded, they open easily, whereas the conventional alloys weld more and more firmly as the current increases. It can be seen from FIG. 2 that the alloy of the present invention has superior welding resistance.

Next, the cutting current value was measured by incorporating the alloy into a vacuum pulp with a rating of 7.2 kV/8 kA, and the alloy of the present invention was compared with the conventional alloy. Contact dimensions are outer diameter 25 mm, inner diameter 13 mm, contact gap 6 mm, contact load 20 mm, vacuum degree 10 torr.
The test conditions were a test voltage of 300 VAC, t, an interruption current of 30.5 A peak, and an opening phase of 90°. Although the tests were conducted several times, the results shown in Table 2 were obtained when the maximum, minimum, and average values of the cutting current values were expressed. The seeds shown in Table 2 correspond to the flies in Table 1. As can be seen from Table 2, the cutting current value of the alloy of the present invention is also improved over the conventional alloy.

Considering the results shown in Table 1, Table 2, and Figure 1 as above, it is clear that Cu, the conventional contact material for vacuum breaker
By adding Te to 7Cr alloy, welding resistance and shear current value, which are important properties of contacts, are improved.
The content of re is 0.05 to 4 chi.

The content of Cu is preferably in the range of 45 to 60% with the remainder being Cr.・,・− Also, if Te is less than 0.05%, there is no effect of adding it and Cu
-It is not possible to improve the welding resistance of Cr-based alloys, and 'r
If e exceeds 4 inches, the welding resistance and shear current characteristics of the Cu-Cr alloy will be extremely good, but the pressure resistance will deteriorate significantly and the contact resistance will increase, which will have a negative effect on the temperature characteristics, so the upper limit is 4%. This has been confirmed through separate experiments.

In addition to the method described in the above example, there is also a method for producing a Cu-Cr-Te alloy in which Cu, Cr, and Te powders are mixed and then sintered. In addition, the contact properties were not satisfied because the theoretical density of
It can also be made by infiltrating U, but this method does not uniformly disperse Te, and furthermore, Te evaporates and scatters, making it difficult to control to obtain the desired alloy composition. The most preferable method is to infiltrate a Cu--Te alloy into a Cr sintered body as described in the Examples.

〔Effect of the invention〕

As explained above in the examples, the contact material for a vacuum breaker of the present invention is a conventional Cu-Cr alloy with 0.05 to 0.05% of Te.
By adding 4% and finely and uniformly dispersing Te in the alloy and setting Cu in the range of 45 to 60%, it is possible to improve welding resistance and cutting current characteristics without impairing conductivity. can.

As a result, the vacuum breaker using the alloy of the present invention does not require the installation of a surge absorber to prevent damage to equipment due to the generation of abnormal voltage caused by the cutting current, and has excellent welding resistance, making it easy to operate. It is also possible to reduce the size and weight of machines, etc., expand the range of application of Cu-Cr contacts, and have great economic effects.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the bonding force and current of the contact material of the present invention.

Claims (1)

[Claims] 1) Te: 0.05-4% p Cu: 45-60
%, the balance being Cr. 2. In the contact material according to claim 1, Cr
A contact material for a vacuum breaker, characterized in that a sintered body is infiltrated with a Cu-Te alloy.