Monitoring circuit for detecting phase failure in a multi-phase electric power supply circuit

Claim 1

APPARATUS FOR PROTECTING AN ELECTRICAL LOAD AGAINST A PHASE FAILURE IN A MULTI-PHASE ELECTRICAL POWER SUPPLY CIRCUIT THEREFOR, COMPRISING A CIRCUIT BREAKER FOR CONNECTING SAID SUPPLY CIRCUIT WITH THE LOAD AND HAVING A TRIPPING COIL OPERATIVE TO OPEN THE CIRCUIT BREAKER UPON ENERGIZATION THEREOF, A THREE PHASE FULL WAVE BRIDGE RECTIFIER CIRCUIT CONNECTED WITH SAID CIRCUIT BREAKER AT THE LOAD SIDE OF THE LATTER AND HAVING A HIGH DIRECT CURRENT OUTPUT VOLTAGE WITH A RELATIVELY LOW SUPERIMPOSED ALTERNATING CURRENT RIPPLE COMPONENT DURING NORMAL OPERATION OF THE SUPPLY CIRCUIT, SAID BRIDGE RECTIFIER CIRCUIT CONVERTING TO A SINGLE PHASE FULL WAVE BRIDGE RECTIFIER CIRCUIT HAVING A RELATIVELY LOW DIRECT CURRENT OUTPUT WITH A HIGH SUPERIMPOSED ALTERNATING CURRENT RIPPLE COMPONENT UPON A LOSS OF VOLTAGE ON A PHASE OF SAID SUPPLY CIRCUIT, A RESISTOR, DIODE AND CAPACITOR CONNECTED IN SERIES ACROSS THE OUTPUT OF SAID BRIDEG CIRCUIT, LAMP MEANS CONNECTED ACROSS SAID DIODE SO AS TO BE ILLUMINATED UPON SAID LOSS OF VOLTAGE OF A PHASE OF THE SUPPLY CIRCUIT, A LIGHT DEPENDENT RESISTOR DISPOSED ADJACENT SAID LAMP MEANS SO AS TO HAVE ITS RESISTANCE REDUCED IN RESPONSE TO ILLUMINATION OF SAID LAMP MEANS, AND MEANS CONNECTING SAID TRIPPING COIL IN SERIES WITH SAID LIGHT DEPENDEN RESISTOR ACROSS SAID CAPACITOR SO THAT SAID COIL IS ENERGIZED TO OPEN THE CIRCUIT BREAKER WHEN SAID RESISTANCE OF THE LIGHT DEPENDENT RESISTOR IS REDUCED.