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Self-monitoring digital solid-state trip release

  • US 4,780,787 A
  • Filed: 07/23/1987
  • Issued: 10/25/1988
  • Est. Priority Date: 08/08/1986
  • Status: Expired due to Fees
First Claim
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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.

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