JPS6235211B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a vacuum shear breaker, and more particularly to a vacuum sheath breaker that has improved pressure resistance and welding resistance, and less occurrence of restriking. Hitherto, high-voltage, large-capacity vacuum shields and disconnectors have been known that have electrode contacts made of a Cu alloy containing 5% by weight or less of welding prevention components (Bi, Pb, Te, etc.). The characteristics of the contact alloys used in these conventional vacuum shields and disconnectors are that they have excellent welding resistance due to the highly dispersed copper with almost zero solid solubility, low melting point, and brittle welding prevention components. , exhibits pressure resistance and shearing characteristics. By the way, vacuum disconnectors have superior features compared to other disconnectors, such as being small, lightweight, maintenance-free, and environmentally friendly.
The scope of its application has expanded year by year, from circuits of 38KV or less, which were commonly used, to even higher voltage circuits (e.g.
Application to circuits of 72KV or higher) is required.
As the pressure increases, contact materials are required to have even higher voltage resistance and excellent non-re-ignition characteristics. In order to increase the pressure resistance of the contact material and prevent restriking, it is desirable to minimize the amount of fragile welding prevention components that cause defects in pressure resistance, and to minimize gas impurities, pinholes, etc. However, when using alloy contacts made by reducing the amount of welding prevention components and slowly cooling using unidirectional solidification to remove gas impurities, pinholes, etc., the welding resistance may decrease and the tripping surface of the contact may deteriorate. Inconveniences such as increased roughness and the formation of protrusions on the contact surface impair the reliability of high-voltage vacuum shields and disconnectors are recognized. The present invention has been made in view of these points, and its purpose is to provide an excellent contact alloy that can reduce the amount of welding components and eliminate gas impurities and pinholes, and has excellent welding resistance and pressure resistance. The purpose of the present invention is to provide a vacuum shear breaker with excellent heat resistance, shearing characteristics, and especially non-restriking characteristics. A feature of the present invention is that in a vacuum shield breaker comprising a fixed electrode, a movable electrode, and an insulating container for vacuum-sealing both electrodes, at least one electrode contact is made of an alloy consisting of 0.01 to 0.5% by weight of Bi, the balance being Cu. The point is that the longitudinal direction of the coarse Cu crystal grains is arranged parallel to the contact surface. Hereinafter, the present invention will be explained in detail with reference to the drawings. FIG. 1 shows an example of the configuration of a vacuum shield disconnector according to the present invention. In the figure, 1 shows a shield and a disconnection chamber, and the shield and disconnection chamber 1 is formed of an insulating material into a substantially cylindrical shape. The insulating container 2 is vacuum-tightly constructed with metal lids 4 and 5 provided at both ends of the insulating container 2 via sealing mechanisms 3 and 3'. A pair of electrodes 8 and 9 attached to opposite ends of conductive rods 6 and 7 are arranged in the sheath cutting chamber 1, with the upper electrode 8 being a fixed electrode and the lower electrode 9 being a fixed electrode. It is a movable electrode. Further, a bellows 10 is attached to the electrode rod 7 of the movable electrode 9, allowing the electrode 9 to reciprocate while keeping the inside of the sheath cutting chamber 1 vacuum-tight. Also, a metal cap 1 is attached to the top of this bellows 10.
1 to prevent the bellows 10 from being covered with arc vapor. Further, 12 is a cylindrical metal container provided in the cutting chamber 1 to cover the electrodes 8 and 9, and prevents the insulating container 2 from being covered with arc vapor. Further, the electrode 9 has a brazed portion 1 on the conductive rod 7, as shown in an enlarged view in FIG.
3 or crimped by caulking. The movable side contact 14' is attached to the movable electrode 9 and is made of a Cu-0.01 to 0.5% Bi alloy, and the longitudinal direction of the Cu crystal grains is parallel to the contact contact surfaces 14a and 14a'. Figure 2 shows the cross-sectional structure of the electrode contact section.
This shows that the longitudinal direction of the Cu crystal grains is parallel to the contact surface. In the present invention, the copper alloy forming the contact point is
The reason for adding Bi is that compared to other welding prevention ingredients such as Pb and Te, Bi has extremely superior welding resistance when added in small amounts, and is necessary for high pressure resistance and non-restriking. This is because it is the most suitable material for reducing the amount of components. However, even if Bi is less than 0.01%, the welding resistance is insufficient, so the lower limit of the amount of Bi added is 0.01%. Also, if it exceeds 0.5%, restriking will occur frequently, so the upper limit is set at 0.5%. Next, the reason why the longitudinal direction of the Cu crystal grains of the electrode contact is made parallel to the contact surface in the present invention will be explained. Since the electrode contact is exposed to an arc when the electrode contacts break, it is necessary to reduce gas impurities as much as possible to improve the breaking characteristics. For this purpose, the contact alloy is alloyed in a vacuum melting furnace using, for example, raw materials from which gas impurities have been removed as much as possible by belt melting refining in vacuum.
After alloying, in order to remove gas impurities, shrinkage cavities, etc., the alloy is slowly cooled using, for example, a unidirectional solidification method. At this time, since the amount of Bi added is small and the cooling is slow, the Cu crystal grains grow along the cooling direction, and some become coarse, for example, several mm in diameter and 10 mm or more in length.
Therefore, when the amount of Bi added is small, if the longitudinal direction of the Cu crystal grains is used perpendicular to the contact surface of the contact, strong welding will occur at the contact and the welding resistance will deteriorate. In addition, if it is forcibly removed, protrusions may be formed on the surface and surface roughness may increase, which is not desirable in terms of pressure resistance. On the other hand, if the longitudinal direction of the Cu crystal grains is parallel to the contact surface, even if the Cu crystal grains on the movable side and fixed side are welded together, the Cu crystal grains will easily cause intergranular fracture, and the welding resistance will deteriorate. It will not be damaged. In addition, the contact surface has little roughness and is excellent in terms of pressure resistance. Therefore, when the amount of Bi added is small and the Cu crystal grains are coarse, it is necessary to arrange the longitudinal direction of the Cu crystal grains to be parallel to the contact surface. If arranged in this way, it is not limited to using the same material for both the two contacts, and even if one electrode is made of, for example, pure copper, sufficient welding resistance can be achieved. Next, examples of the present invention will be described. Table 1 shows Cu and Bi that have been sufficiently degassed by vacuum melting.
The composition ratios (wt%) shown were selected, high-frequency vacuum melting was performed at 1200°C, and cooling was performed by unidirectional solidification to produce 17 types of alloys, including comparative examples. Predetermined test pieces were cut out from each of the alloys thus obtained, and the welding resistance (stripping force) and pressure resistance of these samples were measured, and the results are also shown in Table 1. The welding resistance was measured by applying a load of 100Kg to each disc-shaped sample with an outer diameter of 25mmφ and a pressurizing rod with an outer diameter of 25mmφ and ^{a spherical tip} of 10R.
A half-wave current of 50 Hz and 30 KA was applied in a vacuum of mmHg, and the welding resistance was determined based on the contact tripping force at that time. The measurement data shown in Table-1 is
Dispersion values when measuring five samples are also displayed. In addition, for pressure resistance, the Mi needle mirror-polished by puff polishing is used as the anode, and each mirror-polished sample is used as the cathode, and the gap between the two poles is 0.5.
mm, and the voltage value was measured when a spark was generated by gradually increasing the voltage in a vacuum of 10 ^-6 mmHg. In this case as well, the data are displayed including the dispersion values obtained when the test was repeated 10 times.

[Table] As is clear from the above table, the contacts according to the present invention are:
Has excellent welding resistance with a tripping force of 30 kg or less,
Furthermore, it has a voltage resistance of 62KV or more, and has excellent characteristics as a contact material. On the other hand, in the case of a comparative example in which the longitudinal direction of the Cu crystal grains is perpendicular to the contact surface, the welding resistance is poor despite the presence of a small amount of Bi. Next, Examples 1 to 5 in Table 1 and the welding force of 80 kg
Vacuum breakers using alloys of the same composition as in Comparative Examples 6 to 12 below were fabricated, and a break test of 72 KV and 25 KA was conducted to measure the rate of occurrence of restriking. The results are also shown in Table 2. The data shown in Table 2 is for 20 shear tests. As is clear from Table 2, it was found that the contacts according to the present invention did not cause restriking and had extremely excellent characteristics. As explained above, according to the vacuum shield breaker according to the present invention, by making the contact material have a residual Cu content of 0.01 to 0.5 Bi and making the longitudinal direction of the coarsened Cu crystal grains parallel to the contact surface, the voltage resistance is improved. It can exhibit excellent properties such as anti-re-ignition properties and non-re-ignition properties during welding resistance and shearing properties.

【table】

【table】 [Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of the structure of a vacuum shield disconnector according to the present invention, and FIG. 2 is an enlarged sectional view showing the structure of the contact portion of FIG. 1. DESCRIPTION OF SYMBOLS 1... Shiya disconnection chamber, 2... Insulating container, 8... Fixed electrode, 9... Movable electrode, 6, 7... Conductive shaft, 10
...Bellows, 14'...Movable side electrode contact, 14
a, 14'a...Contact surface of contact.

Claims (1)

[Claims] 1. In a vacuum shield disconnector comprising a fixed electrode, a movable electrode, and an insulating container that vacuum-seals both electrodes, at least one electrode contact has a Bi of 0.01 to 0.5.
% by weight, the balance being Cu, and characterized in that the longitudinal direction of the copper crystal grains is arranged parallel to the contact surface.