Patent ID: 7507932

Claim:
A heavy-duty circuit breaker, which can be filled with a quenching gas, having a first moveable arcing contact piece and a second moveable arcing contact piece, having an auxiliary drive for driving the second arcing contact piece, having an arc which may burn between the arcing contact pieces, having a heating chamber for temporarily storing quenching gas heated by the arc, and having an insulating nozzle, which has a throat for guiding a quenching gas flow, which throat is connected to the heating chamber by means of a channel and can be blocked by one of the two arcing contact pieces, which is referred to as the blocking contact piece, the auxiliary drive being designed such that, during an opening operation, a movement direction reversal of the second arcing contact piece from a movement in opposite directions to a movement in the same direction of the two arcing contact pieces takes place, wherein the auxiliary drive is designed such that, during an opening operation, the movement direction reversal of the second arcing contact piece takes place if the throat is no longer blocked by the blocking contact piece.