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Apparatus and method to detect a series arc fault of an electrical circuit

  • US 8,421,473 B2
  • Filed: 05/10/2010
  • Issued: 04/16/2013
  • Est. Priority Date: 05/10/2010
  • Status: Active Grant
First Claim
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1. An apparatus for a power circuit providing an alternating current to a load, said apparatus comprising:

  • a high frequency current sensor structured to cooperate with said power circuit to provide a high frequency current signal;

    a voltage zero crossing detector structured to cooperate with said power circuit to provide a voltage zero crossing signal;

    a high pass filter structured to provide a filtered current signal from the high frequency current signal;

    a threshold comparator structured to provide an output when the filtered current signal exceeds a predetermined value; and

    a processor structured to receive the voltage zero crossing signal and the output of the threshold comparator and output a trip signal in response to undesired series arcing by detecting an unsymmetrical high frequency signal for a predetermined number of cycles,wherein each of the predetermined number of cycles includes a positive half cycle and a negative half cycle, andwherein said unsymmetrical high frequency signal includes a first high frequency signal for the positive half cycle and a second high frequency signal for the negative half cycle, with an asymmetry between the first and second high frequency signals.

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