SU949732A1 - Vacuum arc chute - Google Patents

Description

(54) VACUUM DIGITAL CAMERA

The invention relates to electrical engineering, namely to vacuum switching devices.

Known vacuum arc chambers (VDK), containing a sheath of metal and dielectric, bellows, screening system, moving and fixed conductors with contacts, which are capable of switching large and small currents in the circuits with reactive load, for this purpose, use contacts that include a material with high vapor pressure 1.1,

Availability in contact material with high vapor pressure reduces the maximum switching capacity VDK to 3-5 kA. The use of overvoltage limiters complicates the design of the switching apparatus and increases its cost.

The closest in technical essence and the achieved result to this is the VDK, which contains a rim of metal and dielectric, an oylfon, a system of shields and current lines with contacts, one of which has a cylindrical protrusion, which with a guaranteed clearance in the corresponding recess in the other contact. When mixing contacts

the projection does not completely come out of the recess, i.e. there is always a constant gap between them. The size of the gap i is chosen such that the overvoltage arising in the circuit due to the cut-off current pierces it and is the most limited. In addition, to reduce dielectric strength on cylindrical surfaces

10 protrusions or notches, sharp protrusions are made 2.

In this VDK, a complex and non-technological contact system is used, which: besides does not provide

Claims (2)

15 high reliability of limiting overvoltages due to the possible transition of a spark discharge to another. Such a transition is unlimited and has arisen; the arcing arc discharge will lead to a change in the size of the gap due to the erosion of the protruding surfaces facing each other into the notches. In addition, such a contact system -. It can not be used in low-voltage BDK, since in this case the gap should be very small (do not exceed tenths of a millimeter). The aim of the invention is to ensure reliable operation and service life 30 VDC. . This goal is achieved by the fact that in a known VDK contacts are made in the form of glasses entering one another, and the guaranteed gap is formed by their side walls made of a material with high electrical resistivity, such as nichrome, on the surfaces of the side walls facing each other. a layer of material with a small work of the electron output (no more than 6 kg) is deposited, for example, thorium oxides. In addition, the side walls can be shaped as a multi-sided prism. The presence of contacts in the form of glasses, which can be made by stamping and drawing, simplifies their design and improves the technology of manufacturing. Manufacturing the side walls of glasses from materials with high electrical resistivity makes it possible to eliminate the transition of the spark discharge to the arc, since when it occurs the current in the circuit is significantly limited by the electrical resistance of the material of the side walls, which provides increased reliability of limiting overvoltage. practically does not change during the whole service life of the VDK. The application of the surface of the side walls of the containers of material with an electron work function of no more than 1 cm J to the PG facing each other allows one to reduce the magnitude of the overvoltage restriction while simultaneously increasing the gap width. This makes it possible to reduce the accuracy requirements for manufacturing VDKs and apply them in low-voltage vacuum switching devices. The drawing shows one of the possible variants of VDK with the proposed contact system. VDK contains a shell comprising dielectric and metal parts. The dielectric part of shell 1 is in the shape of a cylinder. contains metal discs 2, which are vacuum-tightly attached to the ends of the cylinder. A movable conductor 3 passes through the hole in the lower disk 2, which is vacuum-tightly connected to it by a bellows 4 and a guide, a sleeve 5. A screen is attached to the moving current wire 3 b. Through the hole of the upper disk 2, the fixed conductor 7 goes. Inside the VDK shell, the upper disk 2 is attached to the screen 8. At the ends of the movable 3 and fixed 7 conductors, contacts 9 and 10 respectively are shaped in the form of glasses, between which there is a constant gap. The device works as follows about -J at a time. When the contacts between them open, a vacuum arc arises, which goes out when the alternating current passes through zero or earlier, depending on the value of the disconnected current. With the disconnection of currents of several amperes, the arc can cease to exist even at the amplitude value of the current, and the time to reduce it from the amplitude value to zero is. As a result of such a high rate of change of current in an electrical circuit containing reactive loads, significant switching overvoltages occur, the magnitude of which can be several times higher than the electrical strength of electrical equipment insulation. But since the breakdown voltage of a constant gap between the surfaces of the moving and fixed contacts does not exceed the electrical strength of the insulation, the switching overvoltages will penetrate this gap and thereby be limited to the level of a safe value. When the contacts open, the moving conductor may shift if the axis of the chamber does not coincide with the axis of the apparatus. This will change the gap between the side walls of the contacts. To eliminate this phenomenon, the VDK is provided with a guide sleeve, which prevents the movable current lead from shifting above the allowable value. In the closed position, the contacts are in contact with the bases of the contacts and are pressed against each other by the force determined by the pressure difference outside and inside the VDC shell, the effective cross section and the stiffness of the bellows. Application of the proposed VDK in low-voltage switching devices allows significantly (increasing their switching durability. Claim of the invention It is a vacuum interrupter chamber containing a sheath of metal and dielectric, bellows, a system of screens and conductors with contacts, one of which has a cylindrical protrusion the gap in the corresponding recess in another contact / characterized in that in order to increase the reliability of operation and the service life of the vacuum interrupter chamber, the contacts are made in There are glasses in each other, and the gap is formed by their side walls made of a material with high electrical resistivity, such as nichrome, while a layer of material with a low electron work function, such as oxide, is applied to facing surface surfaces of the side walls. tory. 2. Camera pop.1, characterized in that the side walls Contacts are made in the form of a multifaceted prism. Sources of information taken into account in the examination 1. The patent of Great Britain 1142200, cl. H 1 N, 1965. 2. The patent of Germany 2063120, cl. 21 C 35/09, 1970. i (j ° ,,, LL .