Patent ID: 6639330
Filing Date: 2003-10-28
Classification: H01H,H02J

Abstract:
A transfer relay having output means to supply a load that requires uninterrupted operation comprising:means to accept an alternating current electrical power input from two different and independent sources, one said source being a primary source and the second said source being a backup source; a power relay, the coil of said power relay connected across said primary source, said power relay having a pair of double pole, double throw contacts, the first pair of said contacts being in the closed position in which current flows from the primary source to the load and the second pair of said contacts being in the open position when the primary source is energized, said second pair of contacts arranged to allow current flow from said backup source to said load when said contacts are closed; a first control relay and a second control relay, the coil of said first control relay wired in series with the coil of said power relay, said first control relay arranged with a pair of contacts that are held closed while the coil of said relay is energized, said contacts arranged to interrupt current flow to the coil of said second control relay when open and to provide means for the detection of coil failure in said power relay, the coil of said second control relay connected across a line pair from said backup source, the second control relay having contacts that are maintained in an open position when said coil is energized and, upon closing, cause said power relay to switch said electrical power input from said primary source to said backup source in less than one cycle; and alarm means that are activated upon closure of said second control relay contacts to provide warning upon failure of said primary power source.