JPH0510774B2 - - Google Patents

Description

[Detailed description of the invention]

FIELD OF THE INVENTION The present invention relates to a vacuum interrupter, and more particularly to a vacuum interrupter with magnetically driven electrodes. Prior Art A vacuum interrupter equipped with a magnetically driven electrode drives the arc by the interaction between the arc current and the magnetic field generated by making the current path containing the arc into a reciprocating loop, thereby causing local melting of the electrode. The aim is to prevent this from occurring and improve the ability to cut current.
Generally, as shown in FIG. 1, magnetically driven electrodes are formed by forming a pair of electrode rods 1 (only one shown) at the inner end of a pair of electrode rods 1 (only one shown) that are introduced into a vacuum container (not shown) so as to be able to approach and separate from each other. An arc drive unit 2 having a plurality of spiral or screw-shaped arc pedals is fixed to the arc drive unit 2 . A ring-shaped or button-shaped contact part 3 is provided at the center of the arc driving part 2. Incidentally, the electrode material of the vacuum interrupter is required to have the following characteristics (i) to (vi). (i) High shearing performance (ii) High withstand voltage (iii) Low wear (iv) Low shearing value (v) Low contact resistance (vi) Low welding force The electrode material is the heaviest material for a vacuum interrupter, and it is most desirable that it satisfies all of the above characteristics. Conventionally, for example, as disclosed in Japanese Patent Publication No. 45-29935, the arc drive part 2 is made of copper (Cu), and the contact part 3 is made of a Cu-Bi alloy in which Cu contains bismuth (Bi). What was formed is known. However, although such electrodes are excellent in large current carrying capacity, welding resistance, and contact resistance, they are unsuitable for high voltage applications. In addition, for high voltage applications, the contact part 3 was
−20% by weight of Cu described in Publication No. 36121
A material made of 80% by weight of tungsten (W) (hereinafter referred to as "20Cu-80W") is known. However, this electrode has the disadvantage that it is difficult to cut off large currents such as fault currents. On the other hand, Japanese Patent Application Laid-open No. 50-33466 discloses that the contact portion 3
In order to eliminate the drawbacks of the electrode made of a Cu--Bi alloy, an arc drive part 2 made of an iron material, for example, austenitic stainless steel, has been disclosed. However, although this electrode is improved for higher voltages than the one in which the arc driving part 2 is made of Cu, the contact part 3 contains Bi, which has a low melting point and high vapor pressure. There is a limit to increasing the voltage, so 20Cu−80W is applied to the contact part 3.
The withstand voltage was still low compared to those used in the past. OBJECTS OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a vacuum interrupter equipped with magnetically driven electrodes that can be used to interrupt large currents and high voltages. Structure of the Invention In order to achieve the above object, the present invention introduces a pair of electrode rods into a vacuum container so that they can approach and separate from each other, and a contact portion and an arc drive portion are provided at the inner end of each electrode rod. In a vacuum interrupter formed by fixing magnetically driven electrodes, the contact portions of each electrode are made of 20 to 70% by weight of copper and 5 to 5% by weight of chromium.
It is made of a composite metal consisting of 70% by weight and 5 to 70% by weight of molybdenum, and the arc drive part is made of austenitic stainless steel. Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 2 is a longitudinal cross-sectional view of a vacuum interrupter showing an embodiment of the present invention, in which a pair of electrode rods 5, 5 are introduced into a vacuum container 4 so as to be able to approach and separate from each other, and It is generally constructed by fixing magnetically driven electrodes 6, 6 to the inner ends of each electrode rod 5, 5, respectively. That is, the vacuum vessel 4 is made of an iron (Fe)-nickel (Ni)-cobalt (Co) alloy, a Fe-Ni alloy, etc., with two cylindrical insulating tubes 7, 7 made of glass or ceramics fixed at both ends. are joined through one side of the thin annular sealing fittings 8, 8, ... to form a single insulating cylinder, and both open ends are connected to a disk-shaped metal tube through the other sealing fittings 8, 8. It is closed by end plates 9, 9, and is formed by evacuating the inside to a high vacuum (for example, a pressure of 5×10 ^-5 Torr or less). Each of the electrode rods 5 is introduced into the vacuum container 4 from the center of each metal end plate 9 so as to be able to approach and separate from each other while maintaining the airtightness of the vacuum container 4. Note that one side of the electrode rod 5 (upper side in Fig. 2)
is airtightly inserted into one metal end plate 9, and the other metal end plate 9 is inserted in the axial direction (Fig. It is inserted so that it can move freely in the vertical direction). Further, in FIG. 2, 11 and 12 are a shaft shield and a bellows shield, 13 is a main shield, and 14 is an auxiliary shield. As shown in FIG. 3, at the inner end of each electrode rod 5, there is a mounting base 15 made of a highly conductive material such as Cu and shaped like a disk and having a diameter suitably larger than the diameter of the electrode rod 5. , are fixed by brazing through a recess 16 formed on one (lower side in FIG. 3) surface. A recess 17 having a suitably larger diameter than the recess 16 on the one surface is formed on the other surface of the mounting base 15 . As well as being formed,
An arc drive unit 6a having a plurality of spiral arc pedals from the periphery to the center of the arc drive unit 6a for magnetically driving the arc is fixed by brazing via a protrusion protruding from the center of one surface thereof. This arc drive section 6a forms a magnetically driven electrode 6 together with a contact section 6b which will be described later. A circular recess 19 having a diameter suitably larger than the diameter of the electrode rod 5 is formed in the center of the other surface of the arc driving section 6a, which is the opposing surface.
A ring-shaped contact portion 6b protrudes from the opposing surface of the arc drive portion 6a and is fixed by brazing. The arc drive section 6a is made of austenitic stainless steel, such as SUS304, 316L, or the like. In addition, this stainless steel has 2 to 3
% electrical conductivity (IACS%), tensile strength of 49 Kgf/mm ² or more, and hardness of 200 Hv (1 Kg). In addition, the contact portion 6b is made of 20 to 70% by weight of Cu, 5 to 70% by weight of chromium (Cr), and molybdenum (Mo).
It is formed from 5 to 70% by weight of composite metal.
Furthermore, this composite metal has a conductivity of 20-60% and
It has a hardness of 120-180Hv (1Kg). On the other hand, the composite metal forming the contact portion 6b is manufactured by various methods described below. (1) For example, mix a predetermined amount of -100 mesh Cr powder and -100 mesh Mo powder, place this mixed powder in a container made of a material that does not react with Cr, Mo, and Cu (e.g., alumina), and place it on top of the container. Place the Cu block in a vacuum (5x
10 ^-5 Torr), the melting point of Cu (1083
Cu by heating at 1100℃ for 10 minutes at a temperature above ℃)
This is done by infiltrating a porous base material. (2) Powder Cr and Mo, mix them in a predetermined amount, place this mixed powder in a container made of alumina, etc., and place it in a non-oxidizing atmosphere (for example, in a vacuum, hydrogen gas, nitrogen gas, or Argon gas, etc.) at a temperature below the melting point of each metal (for example, below the melting point of Cu if the Cu material is placed on the powder in advance, or Cr if the Cu material is not placed on the powder in advance). (below the melting point of
~60 minutes) to form a porous base material, and then heated and held above the melting point of Cu in the above atmosphere (for example, at 1100°C for about 5 to 20 minutes) to infiltrate Cu into this base material. This is done by combining them into one piece. (3) Powder Cu, Cr, and Mo metals, mix them in predetermined amounts, press-mold this mixed powder to form a mixed element, and then place this mixed element in a non-oxidizing atmosphere. Cu
below the melting point of Cu (e.g. 1000℃) or above the melting point of Cu and below the melting point of other metals (e.g. 1100℃)
The metal powder particles are integrally bonded by heating and maintaining the temperature (about 5 to 60 minutes) at a temperature of 10.degree. Here, the particle size of the metal powder is not limited to -100 mesh (149 μm or less), but may be -60 mesh (250 μm or less). However, when the particle size is larger than 60 meshes, it becomes necessary to increase the heating temperature or lengthen the heating time as the diffusion distance increases when diffusion bonding each metal powder particle, which reduces productivity. This will result in a decline. On the other hand, as the upper limit of particle size decreases, uniform mixing (uniform dispersion of each metal powder particle) becomes difficult, and it is easy to oxidize, making handling troublesome and requiring pretreatment before use. Since there are problems such as the above, there is a limit to the particle size, and the upper limit of the particle size is selected based on various conditions. Further, in both of the above-mentioned manufacturing methods (2) and (3), a vacuum atmosphere is preferable as a non-oxidizing atmosphere since it has the advantage that degassing can be performed simultaneously during heating and holding. However, even when manufactured in a non-oxidizing atmosphere other than a vacuum atmosphere, there is no difference in performance as an electrode for a vacuum interrupter. Next, the component composition manufactured by manufacturing method (1) (50% by weight of Cu, 10% by weight of Cr and 40% by weight of Mo),
Ingredient composition (Cu50wt%, Cr25wt% and
Mo25% by weight) and component composition (Cu50% by weight,
The structural states of each composite metal (Cr40wt% and Mo10wt%) are shown in Figures 4A to D and Figures 5A to 5, respectively.
D and the X-ray photographs shown in FIGS. 6A to 6D. That is, FIG. 4A, FIG. 5A, and FIG. 6A.
The X-ray photographs in Figure B are secondary electron images, and the X-ray photographs in each figure B are characteristic X-ray images showing the dispersion state of Cr, and the white parts scattered like islands are Cr. In addition, each X-ray photograph in Figure C shows the characteristic X that shows the dispersion state of Mo.
In the line image, the white parts scattered like islands are Mo.
Furthermore, the X-ray photographs in each figure D are characteristic X-ray images showing the dispersion state of Cu, with the white portion being Cu. Therefore, Cr and Mo particles diffusely bond with each other to form a porous base material, and Cu is infiltrated into the pores (voids) of this base material to form a strongly bonded composite metal. It can be seen that this is the case. On the other hand, the test results of the component composition, component composition, and various properties of the composite metal of the component composition forming the contact part were as follows. (1) Electrical conductivity (IACS%) 40-50% (2) Hardness 120-180Hv (1Kg) In addition, the arc drive part 6a is made of Sus304,
The electrode shown in Fig. 3 was formed with a diameter of 100 m/m and a contact portion 6b having a ring shape with an inner diameter of 30 m/m and an outer diameter of 60 m/m from a composite metal having a composition. This pair of electrodes 6 was assembled into the vacuum interrupter shown in FIG. 2, and the various performance verification results were as follows. (1) Current shedding capacity The shedding condition is rated voltage 12KV (restart voltage
21KV, JEC-181), it was able to cut a current of 47KA (r・m・s・) at a cutting speed of 1.2 to 1.5 m/s. In addition, the rated voltage is 84KV (restart voltage
143KV, JEC-181), it was able to cut a current of 33KA (r・m・s・) at a cutting speed of 3.0m/s. Table 1 shows the current shedding ability of the conventional product tested under the same conditions and when the contact portion 6b has different component compositions.

[Table] (2) Dielectric strength When we conducted a shock wave withstand voltage test in which the gap was maintained at 30 m/m and a shock wave was applied, the result was ±280 KV.
(variation 10KV). Also,
Similar tests were conducted after multiple cycles of high current (47KA) and after interruptions, but there was no change in dielectric strength. Furthermore, a similar test was conducted after a small advance current (80A) was applied, but there was almost no change in dielectric strength. In addition, each dielectric strength when the contact part 6b was made into a component composition and a component composition showed the same value as the component composition. Table 2 shows the dielectric strength of the invented product and the conventional product.

[Table] (3) Welding resistance After applying a current of 25KA (r・m・s・) for 3 seconds under a pressure of 130Kg (IEC short-time current standard), there was no problem with a static tripping force of 200Kg. The increase in contact resistance after that is 2~
It remained at 8%. Also, under a pressure of 1000Kg,
There was no problem in tripping after applying a current of 50 KA (r·m·s·) for 3 seconds, and the increase in contact resistance after that was only 0 to 5%, indicating sufficient welding resistance. Note that similar effects were obtained when the contact portion 6b had different compositions. (4) Ability to interrupt small delayed currents (inductive loads) The current interrupt value when 30A current is applied is
3.9A (standard deviation σ _o =0.96, number of samples n = 100). Note that when the component composition of the contact portion 6b is taken as the component composition, the average is 3.7A (σ _o =1.26, n=100), and when the component composition is taken as the component composition, the average is 3.9A (σ _o =1.5, n = 100).
showed that. (5) Ability to withstand small leading current (capacitive load) Voltage: 84KV×1.25/√3, 80A small leading current test (JEC-181) was conducted 10,000 times, but no re-ignition occurred. It was 0 times. Note that similar results were obtained when the contact portion 6b had different component compositions. By the way, the component composition of the composite metal forming the contact portion 6b is Cu-20 to 70% by weight, Cr5 to 70% by weight,
When the composition was outside the Mo5 to 70% by weight range, satisfactory properties could not be obtained. That is, if Cu is less than 20% by weight,
The electrical conductivity decreased and the contact provision increased significantly, while above 70% by weight, the welding force and shear value increased significantly and the dielectric strength decreased significantly. Furthermore, when Cr content is less than 5% by weight, the dielectric strength decreases significantly;
When it exceeded 20%, the electrical conductivity and mechanical strength were significantly reduced. Further, when Mo was less than 5% by weight, the dielectric strength was significantly lowered, while when it was more than 70% by weight, the mechanical strength was significantly lowered and the cleavage value became significantly larger. Effects of the Invention As described above, the present invention forms the contact portion of each electrode of a vacuum interrupter with a composite metal consisting of 20 to 70% by weight of Cu, 5 to 70% by weight of Cr, and 5 to 70% by weight of Mo, and Since it is made of austenitic stainless steel, it can significantly improve its ability to conduct and interrupt current compared to conventional types. Moreover, it is possible to obtain excellent dielectric strength, which is almost the same as that of the conventional structure in which the contact portion is formed of 20Cu-80W.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of a conventional magnetically driven electrode.
Fig. 2 is a vertical sectional view showing an embodiment of the vacuum interrupter of the present invention, Fig. 3 is a longitudinal sectional view of the electrode in Fig. 2, Fig. 4 A, B, C, D, and Fig. 5 A, B. ，
C, D and FIGS. 6A, B, C, and D are X-ray photographs showing the structural states of different compositions of the composite metal forming the contact portion, respectively. 4... Vacuum container, 5... Electrode rod, 6... Electrode,
6a... Arc drive section, 6b... Contact section.

Claims (1)

[Claims] 1 A pair of electrode rods are introduced into a vacuum container so that they can approach and separate from each other, and a magnetically driven electrode consisting of a contact part and an arc drive part is fixed to the inner end of each electrode rod. In the vacuum interrupter, the contact portion of each electrode is made of 20 to 70% by weight of copper, 5 to 70% by weight of chromium, and 5 to 70% by weight of molybdenum.
1. A vacuum interrupter characterized in that it is made of a composite metal consisting of: and an arc drive part is made of austenitic stainless steel.