ARC FAULT CIRCUIT INTERRUPTER AND METHOD PROVIDING IMPROVED NUISANCE TRIP REJECTION
First Claim
1. An arc fault circuit interrupter comprising:
- separable contacts;
an operating mechanism structured to open and close said separable contacts;
an arc fault detector structured to detect an arc fault condition operatively associated with said separable contacts, said arc fault detector comprising;
a tuned current sensor structured to sense broadband noise of a current flowing through said separable contacts,a compression circuit including an input of said sensed broadband noise from said tuned current sensor and an output, said compression circuit being structured to compress the dynamic range of said sensed broadband noise,a minimum detector including an input of the output of said compression circuit and an output of the minimum value of said input of said minimum detector, anda processor including a number of inputs and an output, one of said number of inputs being the output of the minimum value of said minimum detector; and
a trip mechanism cooperating with the output of said processor and said operating mechanism to trip open said separable contacts responsive to said detected arc fault condition.
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Accused Products
Abstract
An arc fault circuit interrupter includes separable contacts, an operating mechanism and an arc fault detector structured to detect an arc fault condition operatively associated with the contacts. The arc fault detector includes a tuned current sensor structured to sense broadband noise of a current flowing through the contacts, a compression circuit including an input of the sensed broadband noise and an output. The compression circuit compresses the dynamic range of the sensed broadband noise. A minimum detector includes an input of the compression circuit output and an output of the minimum value of the minimum detector input. A processor includes a number of inputs and an output. One of the inputs is the output of the minimum value of the minimum detector. A trip mechanism cooperates with the output of the processor and the operating mechanism to trip open the contacts responsive to the detected arc fault condition.
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Citations
24 Claims
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1. An arc fault circuit interrupter comprising:
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separable contacts; an operating mechanism structured to open and close said separable contacts; an arc fault detector structured to detect an arc fault condition operatively associated with said separable contacts, said arc fault detector comprising; a tuned current sensor structured to sense broadband noise of a current flowing through said separable contacts, a compression circuit including an input of said sensed broadband noise from said tuned current sensor and an output, said compression circuit being structured to compress the dynamic range of said sensed broadband noise, a minimum detector including an input of the output of said compression circuit and an output of the minimum value of said input of said minimum detector, and a processor including a number of inputs and an output, one of said number of inputs being the output of the minimum value of said minimum detector; and a trip mechanism cooperating with the output of said processor and said operating mechanism to trip open said separable contacts responsive to said detected arc fault condition. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A method of detecting an arc fault condition of an alternating current power circuit having a plurality of half-cycles, said method comprising:
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sensing broadband noise of a current flowing in said power circuit; compressing the dynamic range of said sensed broadband noise; detecting a minimum of said compressed and sensed broadband noise for a plurality of samples for each of said half-cycles; determining a minimum value from said minimum of the compressed and sensed broadband noise for said samples for each of said half-cycles; determining a maximum value from said minimum of the compressed and sensed broadband noise for said samples for each of said half-cycles; determining a dynamic range value from the difference between said maximum value and said minimum value; determining a count of a number of said samples that exceed a first predetermined value for each of said line half-cycles; determining a condition defined by;
(a) said dynamic range value being greater than a second predetermined value, (b) said minimum value occurs at one of either a plurality of the samples at the beginning of a corresponding one of said line half-cycles or a plurality of the samples at the end of the corresponding one of said line half-cycles, and (c) said count of the number of the samples that exceed the first predetermined value being greater than a third predetermined value;increasing an accumulator responsive to said condition being met or decreasing said accumulator responsive to said condition not being met; and detecting said arc fault condition when said accumulator exceeds a fourth predetermined value.
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24. A method of detecting an arc fault condition of an alternating current power circuit having a plurality of half-cycles, said method comprising:
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sensing broadband noise of a current flowing in said power circuit; compressing the dynamic range of said sensed broadband noise; detecting a minimum of said compressed and sensed broadband noise for a plurality of samples for each of said half-cycles; determining a minimum value from said minimum of the compressed and sensed broadband noise for said samples for each of said half-cycles; determining a maximum value from said minimum of the compressed and sensed broadband noise for said samples for each of said half-cycles; determining a dynamic range value from the difference between said maximum value and said minimum value; determining a maximum difference between subsequent values from said minimum of the compressed and sensed broadband noise for each of said line half-cycles; determining a count of a number of said minimum of the compressed and sensed broadband noise that are less than a first predetermined value for each of said line half-cycles plus a number of said minimum of the compressed and sensed broadband noise that are greater than a second predetermined value for each of said line half-cycles; determining a condition defined by;
(a) said dynamic range value being greater than a third predetermined value, (b) the last said count being greater than a fourth predetermined value, (c) said maximum difference being greater than a fifth predetermined value, (d) said maximum difference occurs after a first sample at the beginning of a corresponding one of said line half-cycles, and (e) said maximum difference occurs before a plurality of samples at the end of the corresponding one of said line half-cycles;increasing an accumulator responsive to said condition being met or decreasing said accumulator responsive to said condition not being met; and detecting said arc fault condition when said accumulator exceeds a sixth predetermined value.
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Specification