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Industrial arc fault circuit interrupter and method of detecting arcing conditions

  • US 7,570,465 B2
  • Filed: 12/19/2007
  • Issued: 08/04/2009
  • Est. Priority Date: 12/19/2007
  • Status: Active Grant
First Claim
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1. A circuit interrupter comprising:

  • a number of poles, each of said number of poles comprising a pair of separable contacts;

    an operating mechanism structured to open and close said pair of separable contacts for said number of poles; and

    a trip mechanism cooperating with said operating mechanism to trip open said number of poles, said trip mechanism comprising a processor and further comprising for each of said number of poles;

    a first current sensor structured to sense current flowing through said pair of separable contacts of a corresponding one of said number of poles,a number of second current sensors structured to sense a number of high frequency current signals from the current flowing through said pair of separable contacts of the corresponding one of said number of poles,a number of bandpass filters, each of said number of bandpass filters including an input receiving one of said number of high frequency current signals and an output,a number of peak detectors, each of said number of peak detectors including an input receiving the output of a corresponding one of said number of bandpass filters and an output, anda number of envelope detectors, each of said number of envelope detectors including an input receiving the output of a corresponding one of said number of bandpass filters and an output,wherein said processor is structured to;

    count a count of occurrences of the output of each of said number of envelope detectors exceeding a first predetermined value,maintain a number of temporary values corresponding to the output of each of said number of peak detectors,determine an arc fault trip time as a function of the sensed current flowing through said pair of separable contacts for said number of poles,determine if the output of any of said number of peak detectors is greater than a second predetermined value, and, if so, responsively increase a corresponding one of said number of temporary values by a third predetermined value and, if not, decrease the corresponding one of said number of temporary values by a fourth predetermined value,determine if a predetermined function of said number of temporary values is greater than a fifth predetermined value, and, if so, for each of said number of peak detectors, add the corresponding one of said number of temporary values to an accumulator, and if not, decrease the accumulator by a sixth predetermined value, andcause said operating mechanism to trip open said number of poles if;

    (a) a difference between said count corresponding to the current one of said half cycles having a polarity and said count corresponding to the immediately previous one of said half cycles having the same polarity is at least two, (b) said accumulator is greater than a seventh predetermined value, and (c) the arc fault trip time is reached.

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