Patent ID: 6590757
Filing Date: 2003-07-08
Classification: H02H

Abstract:
An apparatus (10) for protecting an electrical load (14) from a parallel arc fault, comprising:a semiconductor switch (18) for connecting the electrical load to a source of current (12) and having a control input; a current sensor (24) coupled to the semiconductor switch (18) and producing a sensor signal indicative of a magnitude of current flowing to the electrical load (14); and a control circuit (26) connected to the current sensor (24) and the semiconductor switch (18) and responding to the sensor signal by producing a control signal that is applied to the control input, the control circuit having a first mode of operation when the magnitude of current is less than a first threshold wherein the semiconductor switch (18) is maintained in a continuous conductive state, a second mode of operation when the magnitude of current is greater than the first threshold and less than a second threshold wherein the semiconductor switch (18) is rendered non-conductive after a predefined period of time, and a third mode of operation when the magnitude of current is greater than the second threshold wherein the semiconductor switch (18) is alternately pulsed conductive and non-conductive to limit the current through the load (14) to less than the second threshold, the control circuit (26) measures the pulses (74) to determine whether a parallel arc fault has occurred, when the measured pulses (74) are within a predetermined range a parallel arc fault is declared wherein the semiconductor switch (18) is rendered non-conductive.