Speed control circuit for series motors

Claim 1

A CIRCUIT FOR CONTROLLING THE SPEED OF A COMMUTATOR MOTOR HAVING SERIES CONNECTED ARMATURE AND FIELD WINDINGS FED FROM AN A.C. VOLTAGE SOURCE COMPRISING; A SOLID STATE CONTROLLED RECTIFIER HAVING AN ANODE, A CATHODE AND A GATE; MEANS CONNECTING THE ARMATURE WINDING, THE FIELD WINDING, THE ANODE AND THE CATHODE IN SERIES WITH THE VOLTAGE SOURCE; A DIODE CONNECTED ACROSS SAID FIELD WINDING AND OF A POLARITY TO PERMIT FORWARD CURRENT TO FLOW IN SAID FIELD WINDING AFTER THE CONTROLLED RECTIFIER STOPS CONDUCTING TO PROVIDE AN ARMATURE SPEED VOLTAGE HAVING AN EXPONENTIALLY DECREASING TIME FUNCTION; A CAPACITOR; MEANS FOR CHARGING SAID CAPACITOR DURING NEGATIVE HALF CYCLES OF THE SOURCE VOLTAGE TO A VOLTAGE SUBSTANTIALLY EQUAL TO THE PEAK VALUE OF THE A.C. SOURCE VOLTAGE; MEANS FOR DISCHARGING SAID CAPACITOR DURING POSITIVE HALF CYCLES OF THE SOURCE VOLTAGE THROUGH A RESISTANCE TO PROVIDE A POSITIVE CONTROL VOLTAGE HAVING AN EXPONENTIALLY DECREASING TIME FUNCTION; MEANS FOR ADJUSTING THE LEVEL OF SAID CONTROL VOLTAGE; MEANS FOR COMBINING THE CONTROL VOLTAGE WITH THE ARMATURE SPEED VOLTAGE TO PROVIDE A GATE FIRING VOLTAGE; AND MEANS FOR APPLYING SAID GATE FIRING VOLTAGE TO THE GATE AND CATHODE TO CONTROL THE FIRING OF SAID CONTROLLED RECTIFIER.