CIRCUIT ARRANGEMENT FOR INCREASING RESETTING RATION OF DIRECT-CURRENT RELAYS

The connection is used to safely increase the resetting ratio of 1st safety class DC relays in signalling equipment. It consists of an input transformer (2) whose recording winding (2-1) is connected to the source (1) of the output voltage and its reading winding (2-2) is connected to the generator (13). The output winding (2-3) of the output transformer (2) is connected in the cascade through the rectifier (11) of the output current to the exciting winding (12) of the relay. The generator (13) is connected to the reading winding (2-2) of the output transformer (2) through opto-electronic coupling elements (7,9) which switch the voltage of the source (1) of the input voltage to the reading winding (2-2) of the output transformer (2). The connection can also be used as a safety under-voltage relay of DC voltage sources for which it is necessary to evaluate the decrease of voltage under the stated limit.