Abstract: The invention relates to a circuit breaker, preferably for high or medium voltage. The movable conact of each breaker pole is connected, via mechanical means for transmitting movement, to a movable part of an electric motor (6). The movable contact and the means for transmitting movement are arranged in a gas-tight apparatus chamber (31) surrounded by a gas-tight apparatus housing (9) of insulating material such as porcelain. In accordance with the invention the motor (6) is arranged entirely in the apparatus chamber (31). The invention also relates to an electric plant provided with the breaker claimed, uses of the breaker claimed and a method of breaking electric current in which the breaker claimed is used.

Abstract: The invention relates to an electric circuit breaker that includes at least one mobile contact. The contact is connected to operating means that includes an electric motor (6). Movement converting means (16, 17) are provided for converting rotary movement of the motor (6) to translatory movement for linear movment of the mobile contact. The object is to provide an improved movement conversion means. According to the invention, the movement conversion means includes a first body, such as a screw (17), and a second body, such as a nut (16). The threads of the screw (17) and the nut (16) co-act in engagement with each other. The invention also relates to an electric plant that is equipped with such a circuit breaker, to the use of the breaker for breaking electric current, and to a method of breaking electric current with the aid of the inventive circuit breaker.