Method and arc fault circuit interrupter employing a hysteresis value for compressor rumble
First Claim
1. An arc fault circuit interrupter comprising:
- a line terminal;
a load terminal;
separable contacts electrically connected between said line terminal and said load terminal;
a current sensor adapted to sense current flowing between said line terminal and said load terminal and through said separable contacts, said sensed current including a plurality of line cycles;
an arc fault detection circuit adapted to collect a plurality of samples of said sensed current for each of said line cycles, determine a peak current value from said samples of said sensed current for each of said line cycles, determine a difference value for each of said line cycles from the peak current value of a corresponding one of said line cycles less the peak current value of the previous one of said line cycles, change the sign of said difference value on alternate ones of said line cycles, low pass filter the changed sign difference value for each of said line cycles to provide a low pass filtered value for each of said line cycles, determine a peak value from the absolute value of the low pass filtered value for each of said line cycles over a predetermined count of said line cycles, save the peak value as a saved peak value after the predetermined count of said line cycles, determine a hysteresis value as a function of the saved peak value, and generate a trip signal responsive to the sensed current and the hysteresis value; and
an operating mechanism adapted to open said separable contacts responsive to said trip signal.
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Accused Products
Abstract
An arc fault detection circuit collects samples of sensed current, determines a peak current value from the samples for each line cycle, determines a hysteresis value for a compressor load as a function of differences between the peak current values, and generates a trip signal responsive to the sensed current and the hysteresis value. The circuit determines a difference value for each line cycle from the present peak current value less the previous peak current value, low pass filters the difference value to provide a low pass filtered value, determines a peak value from the low pass filtered value, determines that the absolute value of the low pass filtered value is less than a portion of the peak value and responsively saves the peak value, and determines the hysteresis value as a function of the saved peak value. An operating mechanism opens separable contacts responsive to the trip signal.
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Citations
15 Claims
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1. An arc fault circuit interrupter comprising:
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a line terminal; a load terminal; separable contacts electrically connected between said line terminal and said load terminal; a current sensor adapted to sense current flowing between said line terminal and said load terminal and through said separable contacts, said sensed current including a plurality of line cycles; an arc fault detection circuit adapted to collect a plurality of samples of said sensed current for each of said line cycles, determine a peak current value from said samples of said sensed current for each of said line cycles, determine a difference value for each of said line cycles from the peak current value of a corresponding one of said line cycles less the peak current value of the previous one of said line cycles, change the sign of said difference value on alternate ones of said line cycles, low pass filter the changed sign difference value for each of said line cycles to provide a low pass filtered value for each of said line cycles, determine a peak value from the absolute value of the low pass filtered value for each of said line cycles over a predetermined count of said line cycles, save the peak value as a saved peak value after the predetermined count of said line cycles, determine a hysteresis value as a function of the saved peak value, and generate a trip signal responsive to the sensed current and the hysteresis value; and an operating mechanism adapted to open said separable contacts responsive to said trip signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of determining a hysteresis value for an arc fault circuit interrupter, said method comprising:
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sensing a plurality of samples of current for each of a plurality of line cycles; determining a peak current value from said samples of current for each of said line cycles; determining a difference value for each of said line cycles from the peak current value of a corresponding one of said line cycles less the peak current value of the previous one of said line cycles; changing the sign of said difference value on alternate ones of said line cycles; low pass filtering the changed sign difference value for each of said line cycles to provide a low pass filtered value for each of said line cycles; determining a peak value from the absolute value of the low pass filtered value for each of said line cycles over a predetermined count of said line cycles; saving the peak value as a saved peak value after the predetermined count of said line cycles; and determining a hysteresis value as a function of the saved peak value. - View Dependent Claims (11, 12, 13, 14)
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15. An arc fault circuit interrupter for a compressor load, said arc fault circuit interrupter comprising:
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a line terminal; a load terminal; separable contacts electrically connected between said line terminal and said load terminal; a current sensor adapted to sense current flowing between said line terminal and said load terminal and through said separable contacts, said sensed current including a plurality of line cycles; an arc fault detection circuit adapted to collect a plurality of samples of said sensed current for each of said line cycles, determine a peak current value from said samples of said sensed current for each of said line cycles, determine a hysteresis value for said compressor load as a function of differences between the peak current values of said line cycles, and generate a trip signal responsive to said sensed current and said hysteresis value; and an operating mechanism adapted to open said separable contacts responsive to said trip signal.
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Specification