Phase controlled scr circuits for motor speed control system

Claim 1

IN A FULL WAVE SPEED REGULATING SYSTEM, A COMMUTATOR MOTOR HAVING A SERIES-CONNECTED ARMATURE AND FIELD CONNECTED ACROSS A RECTIFIER BRIDGE WHICH BRIDGE IS CONNECTED TO A SOURCE AT A.C. VOLTAGE, SAID BRIDGE HAVING SILICON CONTROLLED RECTIFIERS AND DIODES IN THE LEGS THEREOF WITH THE CATHODES OF THE SILICON CONTROL RECTIFIERS CONNECTED TO SAID MOTOR AND THEIR GATE CIRCUITS CONNECTED TO A UNIJUNCTION TRANSISTOR HAVING AN EMITTER JUNCTION TO BE ALTERNATELY FIRED FOR EACH HALF-WAVE, MEANS FOR CONTROLLING THE FIRING OF THE UNIJUNCTION TRANSISTOR TO FIRE THE SILICON CONTROLLED RECTIFIERS COMPRISING A FULL WAVE RECTIFIER CONNECTED ACROSS THE SECONDARY OF A TRANSFORMER CONNECTED TO THE SOURCE OF A.C. VOLTAGE, A ZENER DIODE AND SERIES-CONNECTED RESISTOR CONNECTED ACROSS THE FULL WAVE RECTIFIER TO PROVIDE A SOURCE OF LOW VOLTAGE HAVING A SQUARED WAVE FORM WHICH PERIODICALLY DROPS TO ZERO, A POTENTIOMETER CONNECTED ACROSS THE LOW VOLTAGE SOURCE, RESISTANCE MEANS CONNECTING A MOVABLE CONTACT OF THE POTENTIOMETER TO THE BASE OF A TRANSISTOR TO APPLY SELECTED NEGATIVE VOLTAGE THERETO TO SELECT THE SPEED OF THE MOTOR, SAID TRANSISTOR HAVING ITS EMITTER AND COLLECTOR CONNECTED ACROSS THE SOURCE OF LOW VOLTAGE AND IN SERIES WITH A RESISTOR AND CAPACITOR, SAID SELECTED NEGATIVE POTENTIAL REDUCING AND CONTROLLING THE RESISTANCE OF THE BASE TO VARY THE FLOW OF CURRENT BETWEEN THE COLLECTOR AND EMITTER AND THE RATE OF CHARGING OF THE CAPACITOR, SAID UNIJUNCTION TRANSISTOR HAVING THE EMITTER JUNCTION CONNECTED TO THE JUNCTION BETWEEN SAID RESISTOR AND CAPACITOR TO BE FIRED BY THE DISCHARGE OF SAID CAPACITOR AND THE FIRE THE SILICON CONTROLLED RECTIFIERS AT A SELECTED PHASE ANGLE WITH RESPECT TO THE A.C. VOLTAGE, AND A BRIDGE CIRCUIT HAVING A TACHOMETER GENERATOR DRIVEN BY THE MOTOR, SAID BRIDGE CIRCUIT BEING CONNECTED ACROSS A PART OF THE RESISTANCE MEANS TO VARY THE SELECTED NEGATIVE VOLTAGE IN ACCORDANCE WITH THE SPEED OF THE MOTOR.