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.