Self-monitoring digital solid-state trip release

Claim 1

A digital solid-state trip release for an electrical circuit breaker with separable contacts comprising: current sensor means for generating analog signals proportional to currents flowing in conductors protected by the circuit breaker; rectifier means for rectifying said analog signals and for producing an analog maximum signal representative of a maximum value of said currents; analog-to-digital converter means having an input receiving said analog maximum signal for generating a corresponding sampled digitized signal; microprocessor-based digital processing unit means, connected to said analog-to-digital converter means, for generating a periodic signal indicative of periodic digital processing of said processing unit, and for generating a first tripping order after at least one of a long delay and short delay when said sample digitized signal exceeds respective predetermined thresholds, said tripping order being delayed according a value of said sampled digitized signal; means for monitoring said digitial processing unit means, including means for detecting said periodic signal, means for generating a microprocessor reinitialization order if said periodic signal is not detected during a first time period, and means for generating a second tripping order if said periodic signal is not detected during a second time period, longer than said first time period; and circuit breaker tripping means for separating said separable contacts, actuated by said first and second tripping orders.