Arc fault detector and method
First Claim
1. An arc fault detector for a circuit comprising:
- a current shunt resistor coupled in series with said circuit; and
an arc discriminator comprising an amplifier sensing a first voltage on a first side of said current shunt resistor, sensing a second voltage on a second side of said current shunt resistor, and producing a first signal proportional to a current flow through said current shunt resistor, said arc discriminator further comprising a change detector receiving said first signal as input and producing an arc fault detection signal as output when said change detector detects a change in said first signal indicative of a presence of an arc fault in said circuit.
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Abstract
The present invention discloses an arc fault detector including a shunt resistor deployed in a circuit being protected, an arc discriminator sensing voltages across the shunt resistor and outputting an arc detection signal when it detects current variations caused by parallel and series arc faults, a signal transformer buffering the arc detection signal and outputting a pulse, a switch transient detector detecting a voltage differential across load switches and outputting a pulsed switch transient detection signal when the voltage differential across load switches exceeds a reference value, a line interrupter such as a static relay, a switch controller including logic gates generating a trip signal based on predetermined criteria, and a manual switch for resetting the line interrupter. A second embodiment of the present invention senses voltage induced in a coil wrapped around a toroidal core to detect current variations in conductors which pass through the center of the toroidal core.
123 Citations
18 Claims
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1. An arc fault detector for a circuit comprising:
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a current shunt resistor coupled in series with said circuit; and
an arc discriminator comprising an amplifier sensing a first voltage on a first side of said current shunt resistor, sensing a second voltage on a second side of said current shunt resistor, and producing a first signal proportional to a current flow through said current shunt resistor, said arc discriminator further comprising a change detector receiving said first signal as input and producing an arc fault detection signal as output when said change detector detects a change in said first signal indicative of a presence of an arc fault in said circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An arc fault detector for a circuit comprising:
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a current monitor detecting a rate of change in electrical current in said circuit and producing a first signal indicative of said rate of change;
a filter connected in series with said current monitor filtering said first signal to substantially eliminate signals outside a selected frequency range, said filter outputting a filtered signal representing changes in said electrical current within said selected frequency range; and
an arc determiner producing an arc detection signal when a voltage level of said filtered signal exceeds at least one threshold. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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17. A method of detecting an arc fault in a circuit comprising:
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coupling a current shunt resistor in said circuit;
monitoring a voltage differential across said current shunt resistor;
detecting a change in said voltage differential;
comparing said change to at least one threshold; and
generating a signal when said change exceeds said at least one threshold.
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18. A method of detecting an arc fault in a system comprising:
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providing a coil wrapped around a toroidal core;
passing at least one conductor of said system through the center of said toroidal core;
detecting a voltage induced in said coil by a change in current flowing through said at least one conductor;
filtering said voltage so as to eliminate signals outside a selected frequency range and to produce a filtered signal;
comparing said filtered signal to at least one threshold; and
generating an arc detection signal when said filtered signal exceeds said at least one threshold.
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Specification