Arc detection using current variation
First Claim
1. An arc detection method for an electric circuit supplying AC line current to a load from an AC source providing an AC waveform of given frequency, comprising sensing changes in AC line current at predetermined points of said AC waveform and generating difference signals representing said changes, generating from said difference signals cumulative difference signals having magnitudes at said predetermined points of said AC waveform derived from said difference signals over a preselected number of cycles of said AC waveform, and responding to given conditions of said cumulative difference signals to generate an arc indicative signal.
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Abstract
In an electric circuit supplying AC line current to a load (30, 31) from an AC source (26) of given frequency providing repetitive cycles, arc detection is provided by sensing cycle to cycle changes in the AC line current. The AC line current is sampled with a harmonic notch filter (72) at a plurality of n phases Θ1 through Θn during each of a plurality of m cycles of the AC source (26), to provide a plurality of currents In,m, where n is the phase and m is the cycle. The differences (In,m)-(In,m-x), where x is a designated number of cycles, provide a plurality of current difference signals. The absolute values of these current difference signals ID are accumulated in a synchronous summer (94) over the m cycles. An arc indicative signal is generated in response to given conditions and given combinations of conditions (116) of the cumulative absolute current difference signals ID. Cycle to cycle changes in AC line voltage are also sensed with a harmonic notch filter (146), and the arc indicative signal is disarmed in response to a given voltage condition. In further embodiments, subcycle changes are sensed.
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Citations
48 Claims
- 1. An arc detection method for an electric circuit supplying AC line current to a load from an AC source providing an AC waveform of given frequency, comprising sensing changes in AC line current at predetermined points of said AC waveform and generating difference signals representing said changes, generating from said difference signals cumulative difference signals having magnitudes at said predetermined points of said AC waveform derived from said difference signals over a preselected number of cycles of said AC waveform, and responding to given conditions of said cumulative difference signals to generate an arc indicative signal.
- 15. An are detection method for an electric circuit supplying AC line current to a load from an AC source of given frequency providing repetitive cycles, comprising sensing cycle to cycle changes in said AC line current and generating difference signals representing said changes, generating from said difference signals cumulative difference signals having magnitudes cycle-to-cycle derived from said difference signals over a preselected number of cycles of said AC line current, and responding to given conditions of said cumulative difference signals to generate an arc indicative signal.
- 31. An arc detection method for an electric circuit supplying AC line current to a load from an AC source of given frequency providing repetitive cycles, comprising sensing cycle to cycle changes in said AC line current and generating difference signals representing said changes, responding to given conditions of said difference signals to generate an arc indicative signal, and sensing a given AC line voltage parameter, and disarming said arc indicative signal in response to a predetermined condition of said parameter.
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39. An arc detection method for an electric circuit supplying AC line current to a load from an AC source of given frequency providing repetitive cycles, comprising:
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sampling AC line current at a phase Θ
1,1 during a first cycle of said AC source to provide a current I1,1 ;sampling AC line current at a phase Θ
1,2 during a second cycle of said AC source to provide a current I1,2, where Θ
1,1 equals Θ
1,2 ;subtracting I1,1 from I1,2 to provide a current difference signal ID1,2-1 ; sampling AC line current at a phase Θ
1,3 during a third cycle of said AC source to provide a current I1,3, where Θ
1,2 equals Θ
1,3 ;subtracting I1,2 from I1,3 to provide a current difference signal ID1,3-2 ; summing ID1,2-1 and ID1,3-2 to provide a cumulative current difference signal thereof; responding to given conditions of said cumulative current difference signal to generate an arc indicative signal. - View Dependent Claims (40, 41, 42, 43, 44, 45, 46, 47, 48)
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Specification