Patent ID: 8170816
Filing Date: 2012-05-01
Classification: H02H

Abstract:
1. An apparatus for interrupting current in an electrical circuit, the apparatus comprising: a current sensing device disposed in the electrical circuit to sense an electrical load, the current sensing device configured to produce an output signal representative of a load current passing therethrough; a detection unit, in signal communication with the current sensing device and configured to receive the output signal produced by the current sensing device, the detection unit being configured and disposed to output a secondary signal based on the output signal, the secondary signal comprising a positive half cycle and a negative half cycle; and a microcontroller coupled to the detection unit, being responsive to computer executable instructions which, when executed by the microcontroller, cause the microcontroller to receive and to decompose the secondary signal for the positive half cycle via discrete wavelet transforms to thereby obtain discrete wavelet coefficients for the positive half cycle, and to decompose the secondary signal for the negative half cycle via discrete wavelet transforms to thereby obtain discrete wavelet coefficients for negative half cycle, and to compute a sum of the discrete wavelet coefficients for the positive half cycle and the negative half cycle, and to compare the sum of the discrete wavelet coefficients for the positive half cycle and the negative half cycle to a predetermined threshold, and to generate a trip signal when the sensed load current is above a predetermined threshold and the sum of the discrete wavelet coefficients for at least one of the positive half cycle and the negative half cycle cooperatively indicate that predetermined threshold conditions for trip signal generation are satisfied.