Electrical circuit breaker with self-expansion and rotating arc

Claim 1

An electrical circuit breaker with self-expansion and rotating arc, housed in a sealed casing filled with an insulating gas with high dielectric strength, notably sulphur hexafluoride, and comprising an arc extinction device arranged in a first extinguishing chamber, capable of communicating by means of exhaust channels with a second adjacent expansion chamber, said arc extinction device of each pole comprising: a system of separable contacts having a movable arcing contact part mounted with sliding in the first chamber and capable of cooperating in a closed position with a fixed or semi-fixed arcing contact part, a breaking zone provided between said fixed and movable arcing contact parts in an opened position, an arc being drawn in said breaking zone when the arcing contact parts separate, a magnetic blow-out coil arranged in the first chamber to generate a magnetic field causing rotation of the arc in the breaking zone, communication ducts inside the hollow arcing contact parts to constitute said exhaust channels for the compressed gas from the first chamber to flow to the second expansion chamber, an electrode to pick up the arc in the breaking zone, the coil surrounding coaxially said first arcing contact part, which is electrically connected with a first end of said coil, a front face of said coil being in contact with said first end, a gap designed to insulate the electrode from the fixed arcing contact and from said front face, and a branch circuit arranged in the first extinguishing chamber outside the coil, in such a way as to connect the electrode electrically to a second opposite end of the coil, said electrode being arranged to pick up a fraction of the arcing current so that the magnetic field generated by the coil in the breaking zone remains appreciably constant when the value of the short-circuit current exceeds a predetermined threshold.