Method and arc fault circuit interrupter employing a hysteresis value for compressor rumble

A method of determining a hysteresis value for an arc fault circuit interrupter, said method comprising:

• 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.

An arc fault circuit interrupter for a compressor load, said 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 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.