Speed control circuits for series motors

Claim 1

A MOTOR CONTROL SYSTEM COMPRISING: (A) A SERIES COMMUTATOR MOTOR HAVING AN ARMATURE WINDING AND A FIELD WINDING, (B) A PAIR OF LEADS ADAPTED FOR CONNECTION TO AN ALTERNATING CURRENT SOURCE, (C) A SOLID STATE CONTROLLED RECTIFIER HAVING AN ANODE, A CATHODE AND A GATE, SAID ANODE AND CATHODE BEING CONNECTED IN SERIES CIRCUIT RELATION WITH SAID ARMATURE AND FIELD WINDINGS BETWEEN SAID LEADS FOR RECTIFYING ALTERNATING CURRENT FROM SAID SOURCE FOR VARIABLY ENERGIZING SAID ARMATURE AND FIELD WINDINGS, (D) A FIRST RESISTOR AND A ZENER DIODE CONNECTED IN SERIES ACROSS SAID LEADS TO ESTABLISH A D.C. VOLTAGE LEVEL EARLY IN EACH CYCLE WHEN THE ANODE VOLTAGE IS POSITIVE WITH RESPECT TO THE CATHODE VOLTAGE, (E) A SECOND RESISTOR AND THE FIELD WINDING CONNECTED IN SERIES ACROSS THE TERMINALS OF SAID ZENER DIODE TO PROVIDE CONSTANT EXCITATION OF THE FIELD WINDING AT THE D.C. VOLTAGE LEVEL INDEPENDENTLY OF THE RESIDUAL FLUX IN SAID FIELD, (F) A CAPACITOR INCLUDING MEANS FOR CHARGING SAID CAPACITOR TOWARD SAID D.C. VOLTAGE LEVEL AT AN ADJUSTABLE TIME RATE TO PROVIDE A CONTROL VOLTAGE HAVING A POSITIVE SLOPING TIME FUNCTION, AND (G) A CIRCUIT MEANS FOR APPLYING TO SAID GATE AND CATHODE A VOLTAGE EQUAL TO THE ALGEBRAIC SUM OF THE CONTROL VOLTAGE AND THE ARMATURE SPEED VOLTAGE.