Abstract: A shunt trip assembly having a tripping solenoid and a locking solenoid selectively blocks movement of the tripping solenoid to prevent inappropriate tripping of a circuit breaker during shock loading thereof. The tripping solenoid includes a tripping plunger that is longitudinally translatable along a tripping path to operatively engage a trip button of the circuit breaker. The locking solenoid includes a locking plunger that is selectively translatable along a locking path to selectively block movement of the tripping plunger, the locking path being substantially perpendicular to the tripping path. A longitudinally-facing first abutment surface on the tripping plunger is engaged by the locking plunger to prevent inappropriate movement of the tripping plunger during shock loading. A peripherally-disposed second abutment surface on the tripping plunger prevents misconfiguration of the shunt trip assembly after the shunt trip assembly has been deenergized.

Abstract: A shock resistant under-voltage release mechanism for a circuit breaker includes a magnetic tripping device resiliently mounted onto a mounting bracket with one or more resilient mounts. The magnetic tripping device includes a plunger that selectively engages a trip button of the circuit breaker when the voltage supplied to a coil of the magnetic tripping device drops below a given preset limit voltage. The resilient mounts each include first and second flanges, with a hub extending between the first and second flanges. The resilient mount is mounted on the mounting bracket of the under-voltage release mechanism such that the hub is disposed against a mounting hole formed in the mounting bracket, and the first and second flanges are disposed against the opposite faces of the mounting bracket. A fastener is slidingly received through an opening formed in each resilient mount and is attached onto an attachment hole formed on a coil frame of the magnetic tripping device.