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Method for discriminating abnormal current including arc current in AC load circuit and apparatus for executing the same

  • US 6,703,842 B2
  • Filed: 01/24/2002
  • Issued: 03/09/2004
  • Est. Priority Date: 01/25/2001
  • Status: Expired due to Term
First Claim
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1. An abnormal current discriminating method in an AC load circuit, comprising the steps of:

  • sampling an alternating current flowing to the AC load circuit in a predetermined cycle and converting the alternating current into a digital value corresponding to its instantaneous current to detect a peak value for each half wave;

    extracting a predetermined transition pattern specified byte combination of fluctuation patterns of peak values of three continuous half waves from the peak value for each half wave thus detected and counting the number of appearances thereof in a restricted predetermined period; and

    comparing the count value with a predetermined threshold and deciding the current to be an arc current when the count value exceeds the threshold; and

    wherein the predetermined transition pattern is specified by four kinds of fluctuation patterns, that is, no fluctuation to an increase, an increase to no fluctuation, no fluctuation to a decrease, and a decrease to no fluctuation in the peak values of the three continuous half waves.

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