In an overload relay, a tripping actuator 12 has a first magnet 18 and a moveable contact carrier 20 has a second magnet 28 mounted opposed to the first magnet. A moveable contact 22 on the moveable contact carrier is urged by repulsion between the magnets, to make a normally closed connection with a stationary contact 24, when the tripping actuator is in an ON position 15 and the contact carrier in a first stable position 26. The magnets pass through an over-center tripping position (T) when the tripping actuator is moved to an OFF position 23 in response to an overcurrent condition sensed by a bimetallic thermal overload sensor 16. The magnets repel each other after passing through the over-center tripping position, to thereby urge the moveable contact into a second stable position 26, away from the stationary contact, to break the normally closed connection with the stationary contact.

Embodiments provide a circuit breaker having a relatively low instantaneous current level at tripping. The circuit breaker includes a tripping mechanism coupled to a moveable electrical contact, the tripping mechanism including a tripping unit having a magnet, a bimetal member extending alongside of the magnet and having a moveable end, and an armature including an engagement portion being moveable as a result of motion the moveable end to trip the circuit breaker upon exceeding an instantaneous current level, and either the armature or the bimetal member includes a non-magnetic separating piece preventing a magnetic short circuit. System and method aspects are provided, as are other aspects.

Embodiments of the present disclosure provide an opening and closing mechanism and a leakage protection device. The opening and closing mechanism comprises: a stationary contact and a movable contact, which contacts the stationary contact at ON-position and separates from the stationary contact at OFF-position; a first magnetic assembly; and a second magnetic assembly that is integrally rotatable about an axis, the second magnetic assembly comprising: an electric conductor onto which the movable contact is mounted; and a magnetic body comprising at least one magnetic portion configured to rotate about the axis under a magnetic force from the first magnetic assembly, to correspondingly drive the movable contact to rotate between the ON-position and the OFF-position, wherein a distance from each of the at least one magnetic portion to the axis is smaller than a distance from the movable contact to the axis. In accordance with embodiments of the present disclosure, the transmission efficiency within the opening and closing mechanism may be boosted, and the movable and stationary contacts are separated faster and by a longer distance, so as to improve the performance of the opening and closing mechanism.