Gas blast circuit breaker

#a. Field of the Invention

#This invention relates to a gas blast circuit breaker having a movable contact, a mating contact and a nozzle aperture through which the movable contact can travel. More particularly, the nozzle aperture is disposed in a wall dividing the switching chamber which generates a quenching gas flow initiated by the arc.

#b. Description of the Prior Art

#FIG. 1 is a view in split cross-section of a gas blast circuit breaker embodying the teachings of the invention; the left side shows the breaker after opening.

#FIG. 2 is a view in cross-section of another embodiment of a gas blast circuit breaker according to the teachings of the invention.

#The gas blast circuit breaker shown in FIG. 1 comprises a hollow, insulating cylindrical switching member 1, which may, for example, be made of porcelain, and the switching chamber 2 of which is filled with sulfur hexafluoride as the gaseous quenching and insulating medium. A movable contact 3 is centered in the interior and cooperates with a mating contact 4, being received therein. Mating contact 4 is connected electrically to a terminal 6 via a current carrying ribbon 5. The terminal 6 is mounted on a cap 7 which closes the switching chamber 2 at the end face of cylinder 1. The cap 7 has a tubular inner support 8 extending into the switching chamber 2 and consists, in its lower part at least, of insulating material. At its lower end, inner support 8 carries a wall 9 which divides the switching chamber 2 into two parts. The wall 9, in turn, supports a nozzle 10 which surrounds the movable contact when it is in the "on" position.

#The upper part of support 8 is cylindrical in shape and guides piston 11 for motion towards and away from wall 9. The piston 11 is loaded in the direction of interruption by springs 12 which are braced against the cap 7. Piston 11 carries the mating contact 4, which occupies the position shown (FIG. 1) to the right of center line 13 in the "on" position and the position shown to the left of center line 13 in the "off" position.

#If movable contact 3 is moved in the direction of the arrow 14 into the "off" position due to an "off" command, then the mating contact 4 and the spring loaded piston 11 follow the movable contact 3 a certain distance, but not so far as to close the space between wall 9 and piston 11. In this process, the gas located between the end face 15 of piston 11 and the wall 9 undergoes compression, or is "precompressed" until the metallic separation between the contacts 3 and 4 takes place. Then the arc drawn in the separation process is supplied with, and cooled by, the compressed gas. In the course of the opening motion, the contact 3 is pulled further down until it leaves the nozzle 10. Then the arc burning in the space between the piston 11 and the wall 9 sets in motion a flow of quenching gas through the nozzle 10 due to the increase in pressure caused by the burning arc.