Universal-motor counter e. m. f. speed control circuit

Claim 1

A CIRCUIT FOR REGULATING THE SPEED OF AN ELECTRIC MOTOR HAVING SERIES CONNECTED ARMATURE AND AT LEAST ONE FIELD WINDING, COMPRISING: (A) POWER LEADS CONNECTED ACROSS SAID MOTOR, (B) ONE OF SAID POWER LEADS CONTAINING IN SERIES A CONTROLLED RECTIFYING DEVICE HAVING A GATE TERMINAL, FOR CONTROLLING THE FLOW OF CURRENT TO SAID MOTOR, (C) REFERENCE CIRCUIT MEANS CONNECTED EFFECTIVELY ACROSS SAID POWER LEADS AND TO SAID GATE TERMINAL FOR DERIVING A REFERENCE VOLTAGE CHARACTERIZED BY A D.-C. COMPONENT AND AN A.-C. RIPPLE, (D) FIELD DISCHARGE CIRCUIT MEANS CONNECTED ACROSS SAID FIELD WINDING OF SAID MOTOR FOR PRODUCING A UNIDIRECTIONAL FIELD CURRENT AND RESULTANT MAGNETIC FIELD AT ALL TIMES, AND (E) SENSING CIRCUIT MEANS FOR DERIVING AN OUTPUT VOLTAGE PROPORTIONAL TO THE GENERATED VOLTAGE OF SAID MOTOR, SAID LAST NAMED CIRCUIT MEANS BEING CONNECTED BETWEEN THE CATHODE OF SAID CONTROLLED RECTIFYING DEVICE AND SAID REFERENCE CIRCUIT MEANS, AND OF A POLARITY TENDING TO OPPOSE THE PORTION OF SAID REFERENCE VOLTAGE APPLIED TO THE GATE OF SAID CONTROLLED RECTIFYING DEVICE, WHEREBY THE DIFFERENCE IN VOLTAGE BETWEEN SAID REFERENCE VOLTAGE AND SAID OUTPUT VOLTAGE DETERMINES THE FIRING POINT OF SAID CONTROLLED RECTIFYING DEVICE.