High-voltage switches with arc preventing or extinguishing devic – Arc preventing or extinguishing devices – Vacuum
Reexamination Certificate
1998-11-10
2002-08-20
Donovan, Lincoln (Department: 2832)
High-voltage switches with arc preventing or extinguishing devic
Arc preventing or extinguishing devices
Vacuum
C218S118000, C218S130000
Reexamination Certificate
active
06437275
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a novel vacuum circuit-breaker, to a vacuum valve for use in the circuit-breaker, and furthermore to electrodes which are used therein.
An electrode arrangement in a vacuum circuit-breaker comprises a pair of a stationary or fixed electrode and a movable electrode. Each of the above fixed and movable electrodes comprises four individual elements of an arc electrode, an arc electrode support which supports the arc electrode, a coil electrode material which extends from the arc supporter, and an electrode rod at the end of the coil electrode.
The above arc electrode is directly exposed to arc when breaking a high voltage and a large current. Desirable characteristics required for the arc electrode are fundamental requirements such as a large current breaking capacity, a high voltage resistance, a low contact resistance (i.e., an excellent electrical conductivity), an excellent fusion resistance, a low contact wear, and a low cutting current value. It is difficult, however, to satisfy all of the above requirements, and hence, in general, there has been used a material in which given preference are the characteristics considered to be particularly important for a specific use, and the other characteristics are sacrificed to some extent. As an arc electrode material for large current and high voltage break, Japanese Patent Application Laid-Open Publication No. 96204/1988 teaches a method of dissolving Cu in Cr or a Cr—Cu skeleton. Furthermore, a similar manufacturing method has also been disclosed in Japanese Patent Post-Examination Publication No. 21670/1975.
The electrode arrangement in a vacuum valve which is located in a vacuum circuit-breaker also comprises a pair of electrodes constituted by a fixed electrode and a movable electrode. Each of the fixed electrode and the movable electrode comprises an electrical contact and an electrode rod extending therefrom, and a plate of a stainless steel or the like is often provided as a reinforcing plate on the back side of the electrical contact.
Cr—Cu composite metals or Cr—Cu composite with small additions of other elements such as W, Co, Mo, V and Nb are frequently used as the materials for the electrical contacts for large current and high voltage break.
The above electrical contacts are manufactured by forming the constituent metal powders or mixture thereof into a compact with predetermined composition, shape, and hole volume. The compact thus formed is subsequently sintered to form a skeleton into which Cu or an alloy flux thereof is forced to permeate by a so-called infiltration method. Alternatively, the compact is given high density in the pre-infiltration sintering process by a so-called powder metallurgy method. The electrical contacts obtained in this manner are further machined into the desired shape.
On the other hand, the electrode rod is formed by cutting a pure Cu material into a predetermined shape.
After each of the elements manufactured as described above is assembled, brazing is performed, thereby combining the elements into individual electrode structures. However, electrodes which are constructed through brazing requires excessive time and effort for assembly due to machining and brazing for every element, and furthermore, brazing deficiencies will lead to electrode breakage or fall-off.
As a solution to the above problems, a so-called one-piece infiltration method has been developed, by which the above electrical contact and electrode rod are combined into one unit in the manufacturing stage. More specifically, a highly conductive metal for forming the electrode rod is placed and held on a skeleton which has been formed to the required composition, shape, and hole volume from the mixed powder of components for the electrical contact. The assembly is heated to infiltrate the highly conductive metal into the electrical contact and to form the electrode rod with the remaining highly conductive metal. This method is disclosed in Japanese Patent Application Laid-Open Publication No. 29461/1995.
SUMMARY OF THE INVENTION
According to the one-piece infiltration method, pre-brazing assembling operations and brazing operations become unnecessary to remarkably reduce the production stages, and furthermore, electrode breakage or fall-off caused by brazing deficiencies is eliminated, thereby providing electrodes of superior reliability and safety. On the other hand, there occurs consumption of the electrical contact component to a certain degree into the electrode rod side due to dispersion and solidification. The skeleton of the electrical contact therefore has to be formed larger by the consumed volume, thus increasing the manufacture cost. Furthermore, the consumed volume of the electrode varies widely due to non-uniformity in composition and hole volume of the skeleton. Consequently, there occurs an irregularity in position of the interface between the electrical contact and the electrode rod, and the manufacturing yield deteriorates.
Further, large ingot piping occurs in the upper portion of post-infiltration ingots. The electrode has to be cut from the material excepting the ingot piping, and the material is largely wasted.
The electrical contact described above is provided with slit grooves for imparting a driving force to arcs generated, thereby moving the arcs to the periphery of the electrode and preventing the arcs from stagnating. The slit grooves divide the electrical contact into vane-shaped segments. These slit grooves are machined with end mills, etc. after the infiltration process. The machining takes much time because the grooves are in a curved shape.
Moreover, there arise further problems that assembling for joining the manufactured electrical contact to the electrode rod requires time, and that because of the use of brazing flux and the necessity of brazing, associated costs are incurred. In addition, application of heat during the brazing causes vaporization of the brazing flux which subsequently adheres to the contact surface, thereby resulting in instability of the current breaking performance.
An object of the invention is to provide a vacuum circuit-breaker, a vacuum valve used in the circuit-breaker and electrodes for the vacuum valve, which can reduce the manufacturing process while being of high performance and compact in size.
The invention features a vacuum circuit-breaker comprising a vacuum valve which has fixed and movable electrodes in a vacuum container, conductive terminals for connecting the respective fixed and movable electrodes in the vacuum valve to the outside thereof, and switching means for driving the movable electrode, wherein the fixed and movable electrodes each comprise arc electrodes, whose entire surfaces, mutually facing each other, are made of an alloy containing a refractory metal and a highly conductive metal, and electrode rods of a highly conductive metal supporting the respective arc electrodes, and each arc electrode and the mating electrode rod are integrally formed by means of solid-phase diffusion bonding, preferably simultaneously with the formation of the arc electrode through sintering.
Further, the invention resides in a vacuum circuit-breaker which is characterized in that the fixed and movable electrodes each have a plurality of grooves which are formed in their surfaces facing each other from the inner sides thereof to the outsides except central portions of the electrodes. Each groove penetrates completely the arc electrode, and a recess is formed in the central portion of the surface of each electrode.
Furthermore, the invention resides in a vacuum valve having the fixed and movable electrodes described above and also in vacuum-valve electrodes comprising these electrodes.
The invention is directed to the vacuum valve having a pair of fixed and movable electrodes in a vacuum container, preferably a cylindrical insulation container, wherein the fixed and movable electrodes comprise compacts serving as arc electrodes, each of which is made through the pressure formation of a shaped body from an
Baba Noboru
Hakamata Yoshimi
Kikuchi Shigeru
Kobayashi Masato
Komuro Katsuhiro
Donovan Lincoln
Hitachi , Ltd.
Mattingly Stanger & Malur, P.C.
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