Circuit breaker with digital solid-state trip unit with optional functions

Claim 1

A digital solid-state trip unit for an electrical circuit breaker comprising: current sensor means for generating analog signals proportional to currents flowing through conductors protected by the circuit breaker, rectifier circuit means for rectifying said signals and for providing a continuous analog signal representative of a maximum value of said currents, an analog-to-digital converter means having an input receiving said analog signal and an output for producing a corresponding sampled digitized signal, microprocessor-based digital processing unit means, to which the digitized signal is applied for providing a long delay trip function and a short delay trip function and for generating a circuit breaker tripping order, when present pick-ups are exceeded by said digitized signal, said order being time delayed in terms of the value of the digitized signal, said digitized processing unit also selectively providing a ground fault protection optional function and a load shedding and restoring optional function, said ground fault or load shedding optional functions being performed by selecting a respective execution program stored in non-volitile memory, a circuit breaker trip means activated by said tripping order, a plurality of switches for providing the digital processing unit means with execution parameters of the tripping functions, and optional function switches for providing the digital processing unit means with execution parameters of a selected optional function.