Patent ID: 7157811
Filing Date: 2007-01-02
Classification: H02J

Abstract:
1. An automatic transfer switch circuit for switching a utility-level line power supplied to a load between a first AC power source and a second AC power source, the automatic transfer switch circuit comprising: a first high frequency transformer electrically connected to a utility-level power line from the first AC power source; a second high frequency transformer electrically connected to a utility-level power line from the second AC power source; and a processing unit electrically connected to each of the first and second high frequency transformers to receive a sensed voltage signal indicative of a level of the utility-level line voltage supplied by the respective power sources and to calculate a frequency of the sensed voltage signal, wherein the processing unit is programmed to determine an actual level of voltage supplied by at least one of the first and second AC power sources based on the sensed voltage signal and the frequency of the voltage signal, and to switch the power applied to the load from one of the first and second power sources to the other of the first and second power sources when the actual voltage applied to the load falls below a predetermined value.