Arc fault detector with limiting of sensed signal to shape response characteristic and circuit breaker incoprorating same
First Claim
1. Apparatus for detecting arc faults in an electric power circuit, said apparatus comprising:
- sensing means sensing current in said electric power circuit to generate a sensed current signal;
a pulse generator generating a pulse signal containing at least one pulse each time an arc is struck in said electric power circuit;
limiting means limiting amplitude of said pulses in said pulse signal to a predetermined limit value;
means generating a time attenuated accumulation of said pulses in said pulse signal; and
output means generating an arc signal when said time attenuated accumulation reaches a predetermined level.
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Accused Products
Abstract
An arc fault detector having a pulse generator generating a pulse each time an arc is struck includes a limiting amplifier which limits the amplitude of the pulses to discriminate against false trips from sizable singular events such as tungsten bulb burnout and turn-on of a cold tungsten lamp controlled by a phased back dimmer. When a time attenuated accumulation of the pulses reaches a predetermined level an arc fault signal which can be used to trip the circuit breaker is generated. The pulse generator of the arc fault detector includes multiple stages of high pass filtering which produces overshoot and therefore additional pulses each time an arc is struck. As only the additional pulses associated with large amplitude arcs exceed a threshold value for inclusion in the time attenuated accumulation, compensation for the reduction in sensitivity to large amplitude arcs imposed by the limiting amplitude is provided.
106 Citations
20 Claims
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1. Apparatus for detecting arc faults in an electric power circuit, said apparatus comprising:
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sensing means sensing current in said electric power circuit to generate a sensed current signal; a pulse generator generating a pulse signal containing at least one pulse each time an arc is struck in said electric power circuit; limiting means limiting amplitude of said pulses in said pulse signal to a predetermined limit value; means generating a time attenuated accumulation of said pulses in said pulse signal; and output means generating an arc signal when said time attenuated accumulation reaches a predetermined level. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A circuit breaker for providing protection against arc faults in an electric power circuit, said circuit breaker comprising:
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separable contacts interrupting current in said electric power circuit when open; operating means opening said separable contacts in response to a trip signal; and arc fault detecting means comprising; sensing means sensing current in said electric power circuit to generate a sensed current signal; a pulse generator generating a pulse signal containing at least one pulse each time an arc is struck in said electric power circuit; a limiting amplifier limiting amplitude of said pulses in said pulse signal to a predetermined limit value; means generating a time attenuated accumulation of said pulses in said pulse signal; and trip means generating a trip signal when said time attenuated accumulation reaches a preselected value. - View Dependent Claims (12, 13, 14)
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15. Apparatus for detecting arcing faults in an electric power circuit, said apparatus comprising:
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sensing means sensing current in said electric power circuit to generate a sensed current signal; high pass filter means and low pass filter means filtering said sensed current signal to generate a pulse signal with at least one pulse each time an arc is struck in said electric power circuit; said high pass filter means comprising at least two high pass filters generating undershoot and therefore additional pulses in said pulse signal each time an arc is struck in said electric power circuit; means generating a time attenuated accumulation of said pulses in said pulse signal; and output means generating an arc signal when said time attenuated accumulation reaches a predetermined level. - View Dependent Claims (16, 17)
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18. A circuit breaker for providing protection against arc faults in an electric power circuit, said circuit comprising:
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separable contacts interrupting current in said electric power circuit when open; operating means opening said separable contacts in response to a trip signal; and arc fault detecting means comprising; sensing means sensing current in said electric power circuit to generate a sensed current signal; high pass filter means and low pass filter means filtering said sensed current signal to generate a pulse signal containing at least one pulse each time an arc is struck in said electric power circuit, said high pass filter means including at least two high pass filters generating undershoot and therefore additional pulses in said pulse signal each time an arc is struck in said electric power circuit; means generating a time attenuated accumulation of said pulses in said pulse signal; and trip means generating a trip signal when said time attenuated accumulation reaches a preselected value. - View Dependent Claims (19, 20)
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Specification