INTERRUPTOR PNEUMATICO

A gas-blast switch, preferably suitable for switching high voltages, has two arc contacts which can be moved relatively to each other along an axis. Also included are a heating volume and a compression volume concentrically formed around the axis. Quenching gas is compressed in the compression volume by means of a compression slider. As soon as the gas pressure is sufficiently high, a part of the quenching gas flows via a back-pressure valve into the heating volume and there assists in blasting an arc drawn between the arc contacts during a switching-off process. The assist is needed primarily when only small currents are involved in which case only comparatively low quenching gas pressure is developed in the heating volume. The switching-off capacity of the gas-blast switch is increased with simultaneous reduction in the needed actuating energy. This is achieved in that the arc contact of a moving contact member has a discharge duct which extends in axial direction from a free end facing a fixed contact member to another end which opens into the expansion. volume. Between the compression volume and the expansion volume a device is provided for controlling the pressure and for refilling the quenching gas located in the compression volume.