High interrupting capacity ground fault circuit breaker

Claim 1

Protective apparatus for connection in series between a source of electrical energy and an external power utilization device to automatically interrupt current flow therebetween upon the occurrence of predetermined fault conditions; said apparatus including the series combination of a circuit breaker, a current limiting fuse device, and ground fault interruption means; said current breaker including a pair of cooperating contacts, manually operable first means for moving said contacts between their engaged and disengaged positions, and an elongated bimetallic member having a first end including pivot means and a second end having a contact tip; said elongated member including second means directly coupled to said first means for automatically moving said contacts to their disengaged position in response to predetermined overcurrent fault conditions causing rotation of said elongated member about said pivot means; third means directly coupled to said elongated member for automatically moving said contacts to their disengaged position responsive to initiating disconnection of said fuse device from said circuit breaker; said circuit breaker having a predetermined interruption characteristic in a maximum permissible rated interruption current value at a rated voltage value to define its maximum kva. capacity, said rated interruption current value being less than the maximum current available from the source; said current limiting fuse device having a predetermined current interruption value and a rated voltage value; said interruption characteristics of said circuit breaker and current limiting fuse device being predeterminately coordinated such that the rated voltage values of said fuse device and said circuit breaker are each significantly less than the voltage of said source; and said predetermined fuse interrupting current value is significantly less than said circuit breaker rated interrruption current, thereby to prevent the subjection of said circuit breaker to an interruption current in excess of said predetermined fuse interrupting value, at said voltage of said source; said ground fault interruption means including an actuatable member and fourth means for detecting a ground fault condition, said actuatable member being energized by said fourth means in response to ground fault conditions in excess of a predetermined value; said actuatable member being actuated directly against said contact tip to rotate said elongated member about said pivot means to operate said second means and automatically cause said contacts to move to their disengaged position, thereby interrupting current flow to said power utilization device in the event of said ground fault conditions.