Protection unit for use with electrical or other apparatus

Claim 1

MEANS FOR OPERATING A RELAY IN THE EVENT OF A FAULT IN A MULTI-PHASE A.C. SYSTEM, COMPRISING IN COMBINATION A PLURALITY OF PAIRS OF INPUT TERMINALS, RECTIFICATION MEANS CONNECTING THE PAIRS OF INPUT TERMINALS, RECTIFICATION MEANS CONNECTING THE PAIRS OF INPUT TERMINALS TO THE PHASES OF THE A.C. SYSTEM RESPECTIVELY WHEREBY THE VOLTAGES DEVELOPED ACROSS THE PAIRS OF INPUT TERMINALS ARE EQUAL WHEN NO FAULT EXISTS IN THE SYSTEM, A FIRST OUTPUT TERMINAL CONNECTED TO ONE TERMINAL OF EACH PAIR OF INPUT TERMINALS, SECOND AND THIRD OUTPUT TERMINALS, A FIRST SERIES OF RECTIFIERS HAVING THEIR ANODES CONNECTED RESPECTIVELY TO THE OTHER TERMINALS OF THE PAIRS OF INPUT TERMINALS AND THEIR CATHODES CONNECTED TO THE SECOND OUTPUT TERMINAL, A SECOND SERIES OF RECTIFIERS HAVING THEIR CATHODES CONNECTED RESPECTIVELY TO SAID OTHER TERMINALS OF THE PAIRS OF INPUT TERMINALS AND THEIR ANODES CONNECTED TO THE THIRD OUTPUT TERMINAL, A ZENER DIODE CONNECTED BETWEEN THE FIRST OUTPUT TERMINAL AND ONE OF SAID OTHER INPUT TERMINALS, AND MEANS CONNECTED BETWEEN THE SECOND AND THIRD TERMINALS FOR OPERATING SAID RELAY WHEN THE VOLTAGE ACROSS THE SECOND AND THIRD TERMINALS REACHES A PREDETERMINED VALUE.