JPS5828336B2 - Contact materials for vacuum shields and disconnectors - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a contact material for a vacuum breaker which is excellent for use with high voltage resistance.

The following characteristics should be satisfied by the contact material of a vacuum breaker:

1) High cutting performance.

2) High pressure resistance.

3) Low contact resistance. 4) Low welding force.

5) The cutoff value is small. 6) Less wear and tear.

However, it is difficult to satisfy all of these characteristics with an actual contact material, and in general, materials are used that satisfy particularly important characteristics depending on the application, while sacrificing other characteristics to some extent.

According to our thinking, among the above characteristics, 1), 2), and 3) are particularly important for contact materials for circuit breakers used in circuits with high voltage and large current capacity.

The present invention provides such a contact material.

Conventionally, CuB1 has been mainly used as a contact material for circuit breakers, but according to our experience, 1% of CuB1
The withstand pressure of the vacuum breaker is considerably lowered by the Bi formed therein.

We focused on Cr as an advantageous contact in the case of high voltage.

It is well known that Cr has a high breakdown voltage in a vacuum, but since it is a heat-resistant metal, it has strong thermionic emission characteristics and cannot be expected to have great breaking performance by itself.

Furthermore, since the conductivity is low and the contact resistance is high, it cannot be used as it is in a circuit breaker with a large current capacity due to the temperature rise.

Our second point of interest is to compensate for these weaknesses of Cr by adding Cu.

Our third point of interest is to produce such an alloy of Cu and Cr by powder metallurgy.

According to the powder metallurgy method, a CuCr alloy in which Cr is uniformly dispersed in a Cu matrix can be easily obtained.

Conventionally, such contact materials have been produced by casting, but by casting, it is difficult to obtain a uniformly dispersed CuCr alloy as described above.

Our fourth point of interest is the use of Cu with an average particle size of 5 μm or more.

Such Cu has less hydrogen reduction loss and lower boiling point impurities than, for example, Cu having an average particle size of about 3 μm.

Therefore, when such Cu is used, it is possible to obtain a contact material with a lower content of both oxygen and low-boiling point impurities.

Needless to say, such contact materials are excellent for high voltage and large current applications.

In addition, when actually manufacturing contacts, it is necessary to prevent metal dust from affecting the human body and others, but compared to Cu with an average particle size of about 3 μm, using Cu with an average particle size of 5 μm or more is more difficult to cause floating and scattering. Therefore, it is also advantageous in terms of measures against metal dust.

Conventionally, contact materials using not only CuCr alloy but also Cu with an average particle size of about 3 μm have had difficulties in terms of oxygen content, low boiling point impurity content, metal dust countermeasures, etc. for the reasons explained above.

Therefore, it is necessary to dissociate and remove oxides and evaporate and scatter low-boiling point impurities by sintering in a high-temperature vacuum atmosphere, which is difficult to do with other manufacturing methods such as hydrogen sintering.

However, as is well known, vacuum sintering furnaces inherently have low operational efficiency and are difficult to equalize, resulting in expensive contact materials.

Needless to say, difficulties in dealing with metal dust remain regardless of the sintering atmosphere.

Our fifth point is to use Cr powder with an average particle size of 100 μm or less.

As mentioned above, we expected Cr to have performance as a high-voltage material.

Therefore, it is necessary that Cr be uniformly dispersed in the Cu matrix, and in that sense it is desirable that the Cr particle size be smaller.

We consider Cr from the same viewpoint as the above consideration for Cu.
The upper limit of the average particle size was examined from the viewpoint of withstand voltage, breaking performance, etc., and it became clear that the average particle size should be 100 μm or less.

Our sixth point of interest is to obtain such a CuCr alloy by sintering in a hydrogen atmosphere as suggested above.

Although Cr is an excellent high-pressure material, it has the weakness of being easily oxidized, making it difficult to use with general casting methods, but oxidation can be prevented by sintering in a hydrogen atmosphere, which has a strong reducing ability. A good contact material can be obtained.

According to our experiments, similarly good CuCr alloys were obtained by vacuum sintering, but in this case, we used Cu with an average grain size of about 3 μm, which causes the above-mentioned difficulties.

Similarly, hydrogen sintering was attempted using Cμ with an average particle size of about 3μ, but there were difficulties in terms of oxygen content and low boiling point impurity content.

However, when Cu with an average grain size of 5 μm or more was used, a similarly good CuCr alloy could be obtained by hydrogen sintering.

The advantages of the hydrogen sintering method compared to the vacuum sintering method are as described above.

An embodiment of the present invention will be described below.

FIG. 1 shows the relationship between Cu% and electrical conductivity.

It can be seen from this that the conductivity of CuCr increases with Cu%.

FIG. 2 shows the relationship between Cu% and withstand voltage.

It can be seen from this that the withstand voltage decreases as the Cu% increases.

This is data obtained with a model tube using contacts with a diameter of approximately 30 mm.

FIG. 3 shows the relationship between Cu% and welding properties.

This data shows the maximum current value at which the contacts open when a constant pressure of 20 kg is applied to the contacts of the model tube, a current is passed for 1 second, and then the contacts are pulled apart with a force of 100 kg.

Figure 4 shows the average particle diameter of Cu, hydrogen reduction loss, and purity, especially p.
The relationship with b content is shown.

Compared to the hydrogen reduction loss of Cu with an average particle size of about 3 μm, the weight loss with an average particle size of about 5 μm decreases to 50% or less.

Similarly, the Pb content is 10% or less.

We also verified the relationship between other properties, such as Cu%, surface hardness, contact resistance, breaking current, 25 KArms L/, and arc time at break, and all showed excellent properties.

Based on the above characteristics, we found that a CuCr alloy made of Cu with an average grain size of 5μ or more and Cr with an average grain size of 100μ or less, obtained by sintering in a hydrogen atmosphere, is very suitable as a contact material for vacuum breakers for high voltage and large current. I confirmed that it was excellent.

According to the present invention described above, it is possible to obtain a contact material for a vacuum breaker that is excellent for use with high voltage resistance.

[Brief explanation of the drawings] Figure 1 is a characteristic diagram showing the relationship between Cu% and true electric rate, Figure 2 is a characteristic diagram showing the relationship between Cu% and withstand voltage, and Figure 3 is a characteristic diagram showing the relationship between Cu% and withstand voltage.
% and the welding properties, and FIG. 4 is a characteristic diagram showing the relationship between the average particle diameter of Cu, the amount of hydrogen reduction, and the PB content.

Claims (1)

[Claims] 1. A contact material for a vacuum breaker, comprising Cu having an average particle size of 5 μm or more and Cr having an average particle size of 100 μm or less, and obtained by sintering in a hydrogen atmosphere.