Patent ID: 8908338
Filing Date: 2014-12-09
Classification: H02H

Abstract:
1. A ground fault circuit interrupt (“GFCI”) device for use with an AC power system that includes a line conductor, a neutral conductor and a transformer, the line conductor and the neutral conductor each coupled between a source and a load, the neutral conductor coupled to ground at the source, wherein the transformer includes a first primary winding coupled in series with the line conductor, a second primary winding coupled in series with the neutral conductor, and a secondary winding, the device comprising: a grounded neutral fault detector circuit coupled to the secondary winding, wherein the grounded neutral fault detector circuit comprises: (a) a driver configured to drive the secondary winding with a multi-frequency AC signal, (b) a circuit component configured to monitor a multi-frequency load signal in the secondary winding, (c) a mixer configured to process the multi-frequency AC signal with the monitored multi-frequency load signal to generate a processed signal, (d) a low-pass filter configured to extract a DC signal from the processed signal, and (e) a controller configured to provide a first detection signal if the extracted DC signal exceeds a predetermined threshold.