Transistorized magnetic amplifier control for electromagnetic coupling

Claim 1

AN ELECTRIC CONTROL FOR AN ELECTROMAGNETIC COUPLING APPARATUS HAVING A DRIVEN MEMBER, A DRIVING MEMBER, A ROTATING SHAFT AND A FIELD COIL FOR REGULATING THE SPEED OF SAID SHAFT COMPRISING A GENERATOR DRIVEN BY SAID SHAFT PRODUCING A SIGNAL VOLTAGE PROPORTIONAL TO SAID SHAFT SPEED, A MAGNETIC AMPLIFIER MEANS HAVING A POWER WINDING CIRCUIT, A RELATIVELY FIXEDLY ENERGIZED BIAS CIRCUIT AND A DIRECTLY ENERGIZABLE CONTROL CIRCUIT, AN OUTPUT CIRCUIT CONNECTING SAID POWER WINDING CIRCUIT TO SAID FIELD COIL AND AN A.C. SUPPLY SOURCE CONNECTED TO SAID POWER WINDING CIRCUIT, AND A SPEED RESPONSIVE TRANSISTOR PREAMPLIFIER MEANS INCLUDING AT LEAST ONE TRANSISTOR HAVING AN EMITTER-COLLECTOR CIRCUIT CONNECTED TO SAID CONTROL CIRCUIT, SAID TRANSISTOR PREAMPLIFIER COUPLED TO SAID GENERATOR SIGNAL VOLTAGE FOR CONTROLLING ENERGIZATION OF SAID CONTROL WINDING THEREBY PROVIDING SENSITIVE EXCITATION OF SAID FIELD COIL FOR REGULATING SAID SHAFT SPEED, AN ELECTRICAL MOTOR COUPLED TO SAID APPARATUS, SAID MAGNETIC AMPLIFIER FURTHER INCLUDING A TORQUE LIMITING CIRCUIT, SAID TORQUE LIMITING CIRCUIT COMPRISING A TORQUE LIMITING WINDING, A SECOND A.C. SUPPLY SOURCE CONNECTED TO SAID TORQUE LIMITING WINDING, SAID TORQUE LIMITING WINDING BEING RESPONSIVE TO ENERGIZATION ONLY AT THE INSTANCE OF A TORQUE VOLTAGE SIGNAL IN EXCESS OF A FIXED PREDETERMINED POTENTIAL.