Control of series motors

Claim 1

IN AN ELECTRIC SYSTEM OF CONTROL, IN COMBINATION, A DIRECT CURRENT GENERATOR HAVING AN ARMATURE WINDING AND A FIELD WINDING, A DIRECT CURRENT MOTOR OF THE SERIES TYPE HAVING AN ARMATURE WINDING AND A FIELD WINDING CONNECTED IN SERIES WITH THE MOTOR ARMATURE WINDING, A LOOP CIRCUIT INCLUDING THE GENERATOR ARMATURE WINDING, THE MOTOR ARMATURE WINDING, AND THE MOTOR SERIES FIELD WINDING, CONTROL MEANS RESPONSIVE TO AN ELECTRIC CONDITION IN THE LOOP CIRCUIT, SAID CONTROL MEANS HAVING AN OUTPUT CIRCUIT, SAID OUTPUT CIRCUIT INCLUDING A PAIR OF POTENTIOMETERS CONNECTED, THROUGH A COMMON TERMINAL BETWEEN THEM, IN SERIES WITH EACH OTHER IN THE OUTPUT CIRCUIT TO THUS HAVE A VOLTAGE DROP ACROSS THE POTENTIOMETERS THAT IS A FUNCTION OF THE ELECTRICAL CONDITION IN THE LOOP CIRCUIT, EACH OF SAID POTENTIOMETERS HAVING AN INDEPENDENTLY ADJUSTABLE TAP, A MAGNETIC AMPLIFIER HAVING MAIN WINDINGS AND THREE CONTROL WINDINGS, A ZENER DIODE, AND ADJUSTABLE RESISTOR AND ONE OF THE CONTROL WINDINGS ALL CONNECTED IN SERIES ACROSS THE INDEPENDENTLY ADJUSTABLE TAPS, AN ADJUSTABLE RESISTOR AND A SECOND OF THE CONTROL WINDINGS CONNECTED IN SERIES ACROSS ONE INDEPENDENTLY ADJUSTABLE TAP AND THE COMMON TERMINAL BETWEEN THE POTENTIOMETERS, AND ADJUSTABLE RESISTOR, AND THE THIRD OF SAID CONTROL WINDINGS CONNECTED IN SERIES TO A SUITABLE ADJUSTABLE VOLTAGE SUPPLY OF DIRECT CURRENT, EXCITATION MEANS HAVING OUTPUT CIRCUIT MEANS CONNECTED TO THE FIELD WINDING OF THE GENERATOR AND HAVING CONTROL CIRCUIT MEANS FOR CONTROLLING THE CURRENT OUTPUT OF THE OUTPUT CIRCUIT MEANS, SAID CONTROL CIRCUIT MEANS BEING INTERCONNECTED WITH THE MAIN WINDINGS OF THE MAGNETIC AMPLIFIER MEANS, THE CHARACTERISTICS AND ADJUSTABLE OF THE CIRCUITRY INCLUDING THE CONTROL WINDINGS BEING SUCH THAT THE GENERATOR HAS A VOLTAGE OUTPUT THAT VARIES WITH RESPECT TO LOAD CURRENT FROM A SELECTED RELATIVELY LOW VALUE TO A RELATIVELY HIGH VALUE AND THEN BACK DOWN TO A LOWER VALUE AS CURRENT VALUES OF FULL LOAD AND ABOVE ARE APPROACHED, WHEREBY THE MOTOR SPEED REMAINS NEARLY CONSTANT FROM NO-LOAD TO FULL-LOAD.