Controlled rectifier supply for series motor speed control system

Claim 1

A MOTOR CONTROL SYSTEM COMPRISING: (A) AN ALTERNATING CURRENT SOURCE, (B) A FULL-WAVE RECTIFIER HAVING AN INPUT CONNECTED TO SAID ALTERNATING CURRENT SOURCE AND HAVING POSITIVE AND NEGATIVE OUTPUT TERMINALS, (C) A MOTOR HAVING FIRST AND SECOND INPUT TERMINALS, THE ARMATURE AND FIELD WINDINGS OF SAID MOTOR BEING CONNECTED IN SERIES BETWEEN SAID FIRST AND SECOND INPUT TERMINALS, SAID SECOND INPUT TERMINALS OF SAID CONNECTED TO THE NEGATIVE OUTPUT TERMINAL OF SAID RECTIFIER, (D) A SEMICONDUCTOR CONTROLLED RECTIFIER HAVING AN ANODE, A CATHODE AND A GATE, SAID ANODE BEING CONNECTED TO THE POSITIVE OUTPUT TERMINAL OF SAID RECTIFIER, SAID CATHODE BEING CONNECTED TO THE FIRST INPUT TERMINAL OF SAID MOTOR, (E) A FIRST CAPACITOR AND A FIRST RESISTOR CONNECTED IN SERIES ACROSS THE FIRST AND SECOND INPUT TERMINALS OF SAID MOTOR, (F) A SECOND RESISTOR AND A SECOND CAPACITOR CONNECTED IN SERIES IN THE NAMED ORDER BETWEEN SAID ANODE AND SAID CATHODE, (G) A UNIDIRECTIONAL CONDUCTIVE THRESHOLD TRIGGER DEVICE CONNECTED BETWEEN SAID GATE AND THE JUNCTURE OF SAID SECOND RESISTOR AND SAID SECOND CAPACITOR, (H) MEANS CONNECTED BETWEEN SAID SECOND INPUT TERMINAL AND SAID GATE TO APPLYING A VOLTAGE REFERENCE THERETO, SAID MEANS BEING ELECTIVELY ADUSTABLE TO PROVIDE SEVERAL DIFFERENT MAGNITUDES OF SAID VOLTAGE REFERENCE WHEREBY A PLURALITY OF NO-LOAD SPEED SETTINGS ARE AVAILABLE.