A pressure trip unit for an electrical switch, including an actuating element and at least one flow channel per electrical pole, is disclosed. In an embodiment, the at least one pole of the electrical switch includes at least two switching contacts for making or disconnecting a flow path. The switching contacts of the at least one pole of the electrical switch are disconnectable via the actuating element which can respond to a pressure generated in a disconnection zone of the, in each case, two switching contacts by an electric arc drawn in the event of an electrodynamic recoil of the switching contacts. Further, the disconnection zone is connectable to the actuating element via the flow channel, the at least one flow channel including a nonreturn valve to permit a flow only from the disconnection zone in the direction of the actuating element.

Provided is a circuit breaker with a single pole breaking unit including a housing, a movable contact provided in the housing, a fixed contact provided in the housing and contacting or separated from the movable contact, and an extinction unit provided in the housing and configured to extinguish an arc generated when the movable contact and the fixed contact are separated. At least one arc gas discharge passage is formed in the housing to allow an arc gas generated when the movable contact and the fixed contact are separated to be discharged.

In present disclosure, a movable bar guide portion is formed to protrude toward a movable bar in a shaft having a movable bar, and when a fault current is applied and the movable bar is rotated due to electromagnetic repulsion force, the movable bar and the movable bar guide portion contact each other, and thus, when the movable bar is rotated through the movable guide portion, movement of a rotation center of the movable bar is minimized.

A circuit breaker having first and second electrical contacts configured to generate an electrical arc upon being separated, an arc chamber surrounding at least a portion of a space between the first and second electric contacts, at least one expansion chamber positioned proximate to the arc chamber, and an arc pressure control valve assembly configured to allow threshold-based flow into and out of the at least one expansion chamber. An arc pressure control valve assembly and method of operating a circuit breaker are described, as are other aspects.

A circuit breaker having first and second electrical contacts configured to generate an electrical arc upon being separated, an arc chamber surrounding at least a portion of a space between the first and second electric contacts, at least one expansion chamber positioned proximate to the arc chamber, and an arc pressure control valve assembly configured to allow threshold-based flow into and out of the at least one expansion chamber. An arc pressure control valve assembly and method of operating a circuit breaker are described, as are other aspects.