A movable contact is adapted to engage with and disengage from a fixed contact within a circuit breaker housing. A contact arm, coupled to the movable contact, is caused to trip when appropriate means are actuated. The invention resides in apparatus for actuating such means including a ferromagnetic material armature latch partially rotatable about a housing axis. The latch has a first retaining means and a first coupling surface. A latch member, partially rotatable about a housing axis, has a second retaining means and a second coupling surface adapted to couple with the first coupling surface. Further, the latch member is adapted to recouple the second coupling surface subsequent to it becoming uncoupled from the first coupling surface. A spring couples the two retaining means. An electrical circuit, including the contacts, is responsive to an overload current through the circuit breaker for causing the armature latch to partially rotate, uncoupling the two coupling surfaces, whereupon the spring causes the latch member to rotate with an impetus, actuating the coupled means, thereby tripping the contact arm and opening the contacts.
A molded case thermal-magnetic circuit breaker having improved low current magnetic trip response pivotally arranges the magnet within the circuit breaker thermal-magnetic trip system for controllably moving toward the latching armature assembly. The movement of the magnet decreases the magnetic separation distance between the magnet and the latching armature to optimize the magnetic trip forces and thereby enhance low current magnetic trip response.
A bimetal controlled circuit breaker includes a current bus that is electrically connected in series with the bimetal element. The current bus extends parallel to the bimetal element in the deflection plane of the latter and is rigid relative to the bimetal element. The deflection of the bimetal element is supported by the action of electrodynamic forces. In order for the circuit breaker to be suitable for greater current intensities and the effect of the electrodynamic forces to be better utilized, the bimetal element is electrically connected in parallel with a shunt path.
