Noncontact solenoid for miniature circuit breakers with a movable frame and magnetic coupling
A touchless magnetic-only coupled solenoid trip system for a miniature circuit breaker achieves magnetic tripping using a floating plunger assembly in a solenoid coil/housing to narrow a magnetic gap between plunger and trip assembly to cause the magnetic trip The floating plunger of the solenoid can also move out of the way if the bimetal bends to cause a thermal trip.
1. A circuit breaker trip mechanism comprising:
a trip assembly including a ferromagnetic yoke and a latch plate attached to the yoke;
a trip lever held in the latch plate;
a solenoid with a coil and a housing for the coil, and
a plunger assembly of ferromagnetic material with a movable frame and a plunger rod attached to the frame,
and the plunger rod passing through and floating in the solenoid coil when the solenoid is not activated;
and the solenoid coil mounted adjacent to the ferromagnetic yoke at a known distance;
whereby activating the solenoid pulls the frame to the housing of the solenoid coil in a direction toward the trip assembly thus placing the plunger rod at a magnetic gap distance from the trip assembly sufficient to magnetically attract the at least one of the ferromagnetic yoke and the latch plate to delatch the trip lever and trip the breaker.
2. The circuit breaker trip mechanism according to claim 1 wherein the frame and plunger rod are integrated into a single piece.
3. The circuit breaker trip mechanism according to claim 1 wherein the frame is U-shaped.
4. The circuit breaker trip mechanism according to claim 1 wherein the frame and plunger rod are formed from a single material.
5. The circuit breaker trip mechanism according to claim 1 further including a bimetal within the trip assembly, the plunger assembly facing the direction of yoke movement during a bimetal trip, and wherein the plunger assembly will yield under a motion of the bimetal causing a trip event.