Arc fault detector immune to dimmer transients and a circuit breaker incorporating the same

Abstract From the Canadian patent

Tripping of a circuit breaker by an arc fault detector is blocked by a disable circuit upon detection of a transient associated with cold turn-on of an incandescent bulb powered by a dimmer. The peak value of pulses generated by the bandpass filter of the arc detector in response to step increases in the ac current is decayed approximately exponentially. The amplitude of each pulse is compared with upper and lower percentage limits of the decaying peak value. If the amplitudes of the pulses remain below the upper threshold for about 3 to 4 half cycles and exceed the lower threshold each half cycle a dimmer transient is identified and logic is set to block generation of a false arc signal.