Circuit interrupter including an electric arc monitoring circuit

An arc detection circuit coupled to an electric conductor and generating an arc signal in response to a current within the conductor generated in response to an electric arc, the circuit comprising:

• a transducer coupled to the electric conductor to generate a first signal representative of the current within the conductor;
• a variable frequency filter circuit having a filter frequency which changes in response to a control signal, the filter being coupled to the output to generate a second signal having a plurality of amplitudes representative of the current at a respective plurality of frequencies;
• and
• a threshold sensing circuit coupled to the variable frequency filter circuit to generate the arc signal when a plurality of the amplitudes representative of the currents at the respective plurality of frequencies within a range exceed at least one threshold amplitude.

An arc detector comprising:

• generating means for generating a first signal representative of an electric arc in an electrical conductor;
• filtering means for filtering the first signal at a plurality of frequencies to generate a second signal;
• monitoring means for monitoring the second signal to generate a third signal representative of the amplitude of the second signal within a range of the plurality of frequencies;
• and
• detection means for generating an arc detection signal when the third signal is representative of arcing within the electrical conductor,
• wherein the filtering means comprises a first variable frequency filter which has a first center frequency which changes from a first frequency to a second frequency, the plurality of frequencies being between the first and second frequencies, and the first variable frequency filter being coupled to the generating means to produce the second signal having amplitudes which represent the current at the plurality of frequencies.

A circuit interrupter for interrupting the flow of current within at least one electrical conductor in response to arcing produced by current flow in the electrical conductor, the interrupter comprising:

• a switching device coupled to the electrical conductor and operable to open the circuit defined by the electrical conductor in response to a trip signal;
• a transducer coupled to the electrical conductor to generate a first signal representative of the electric current in the electrical conductor;
• a variable frequency filter coupled to the transducer to generate a second signal representative of the first signal at a plurality of frequencies within a first range;
• a monitoring circuit coupled to the variable frequency filter to generate a third signal representative of the power of a portion of the second signal, wherein the portion is generated from a second range of the plurality of frequencies in the first range;
• and
• a trip circuit coupled to the switching device and the monitoring circuit to apply a trip signal to the switching device when the third signal is representative of an energy level of the portion of the second signal representative of arcing in the electrical conductor.

A circuit interrupter comprising:

• switching means for opening a circuit including an electrical conductor in response to a trip signal;
• sensing means for generating a first signal representative of electric current in the electrical conductor;
• filtering means for generating a second signal representative of the first signal filtered at a plurality of frequencies in a first range;
• monitoring means for generating a third signal representative of the power of a portion of the second signal, wherein the portion is generated from a second range of the plurality of frequencies in the first range;
• and
• trip means for applying a trip signal to the switching means when the third signal is representative of an energy level of the portion of the second signal representative of arcing in the electrical conductor,
• wherein the filtering means comprises a first variable frequency filter which has a first center frequency which changes from a first frequency to a second frequency, the plurality of frequencies being between the first and second frequencies, and the first variable frequency filter being coupled to the generating means to produce the second signal having amplitudes which represent the current at the plurality of frequencies.

An electric arc detection method comprising the steps of:

• generating a first signal representative of an electric current in an electrical conductor;
• filtering the first signal at a plurality of frequencies to generate a second signal;
• and
• monitoring the second signal to generate a third signal representative of the power of the second signal within a range of the plurality of frequencies,
• wherein the step of filtering further comprises the step of cycling between the first and second frequencies at a constant rate over a first time period.