Abstract: A high power d.c. breaker for connection into a d.c. carrying high-voltage line (L), has two normally closed and electrically series-connected mechanical breaks (BSI, BSII) adapted to be traversed by the line current (I) and to be opened for breaking the current. A capacitor (CB) is connected in parallel with the series connection of the breaks. A semiconductor member (HO) is connected in parallel with one of the breaks (BSI). Upon opening the breaks, a control member (SO) controls the semiconductor member such that a zero crossing of the current through the second break (BSII) is obtained, whereby the line current (I) is commutated over to the capacitor. (FIG.

Abstract: In a means for detecting the wear of a current interrupting contact (4) there is used a light conductor (12) as a connecting link between the contact (4) and a detector (20) arranged at ground potential. The light conductor is inserted into an aperture (11) provided from the rear side of the contact, the bottom of said aperture being positioned at the level corresponding to a worn out contact. When the wear has grown so great that the light conductor (12) is exposed, the light or heat of the breaking arc will generate or interrupt a light signal, which via the light conductor is transmitted to the detector.

Abstract: The invention relates to an oil damping device intended to be used in operating mechanisms for puffer-type SF.sub.6 breakers where there is a risk that the contact movement is reversed during an opening operation with great current. The damping device comprises a piston which is attached to a piston rod and is movable in a damping cylinder. The damping device is double-acting and the movement is damped against the two end positions of the piston (corresponding to the closed and open position, respectively, of the circuit breaker) by forcing oil to flow out through restricted openings in the damping cylinder. The damping cylinder is movable inside an additional cylinder between a rest position and a lock position. Upon an opening operation, the damping cylinder is automatically brought to the lock position where it is temporarily retained by a latching member.

Abstract: A puffer type circuit breaker is provided with a pump means consisting of a piston and a cylinder for producing a blast of arc-extinguishing gas. The piston is joined to one contact of the circuit breaker and the cylinder to the other contact. Both contacts are connected to an operating device which is adapted, during the first part of a breaking operation, to move the contacts in opposite directions away from each other, whereupon one contact and the piston joined thereto are returned to the initial position.

Abstract: A puffer type circuit breaker is provided with a pump means consisting of a piston and a cylinder for producing a blast of arc-extinguishing gas. The piston is axially displaceable against a spring force, and the cylinder is joined to the movable contact of the circuit breaker and arranged, during a breaking operation, to compress the gas in the cylinder space of the pump means to achieve a blast of extinguishing gas towards the contact area. A spring holds the piston pressed against a stop in the closed as well as the open position of the circuit breaker. The spring has such a high pre-stress that the piston only moves upon breaking of short-circuit currents.