Patent ID: 7161775

Claim:
A circuit breaker for interrupting current in an electrical system, said circuit breaker comprising: separable contacts adapted to interrupt said current in said electrical system; a trip mechanism adapted to trip open said separable contacts in response to a trip signal; and a trip circuit outputting said trip signal, said trip circuit comprising: a circuit adapted to generate a current signal representative of said current in said electrical system, to rectify said current signal to provide a rectified current signal and to track an envelope of said rectified current signal, a first arc fault detector circuit including a first output, a second arc fault detector circuit comprising: a first circuit adapted to detect when an absolute value of said current signal is less than a first predetermined value and output a signal after a first time period, a comparator adapted to compare said signal after a first time period to the envelope of said rectified current signal, in order to provide a second output with a pulse, which persists for a relatively longer time for a relatively small value of said envelope, and which persists for a relatively shorter time for a relatively large value of said envelope, and a second circuit adapted to enable the second output of said comparator if said rectified current signal exceeds a second predetermined value, and to disable the second output of said comparator after said rectified current signal is below said second predetermined value for a second time period, and an accumulator including an output having said trip signal, the output of said accumulator being responsive to the first output of said first arc fault detector circuit and to the second output of said comparator.