Control system for series-wound alternating current motors

Claim 1

A CONTROL SYSTEM FOR A SERIES-WOUND ALTERNATING CURRENT MOTOR COMPRISING: AN ALTERNATING CURRENT REGULATING MEANS HAVING A POWER INPUT TERMINAL FOR CONNECTION TO A SOURCE OF ALTERNATING CURRENT, A POWER OUTPUT TERMINAL FOR CONNECTION TO A MOTOR CIRCUIT, AND MEANS FOR ACCEPTING A CONTROL SIGNAL FOR CONTROLLING THE POWER FLOW BETWEEN SAID TERMINALS; A MOTOR CIRCUIT INCLUDING THE SERIES CONNECTION OF AN ARMATURE AND A FIELD WINDING FOR CONNECTION TO SAID POWER OUTPUT TERMINAL AND A SOURCE OF ALTERNATING CURRENT; POTENTIAL SENSING MEANS COUPLED IN PARALLEL WITH AT LEAST A PORTION OF SAID MOTOR CIRCUIT; A PHASE DISCRIMINATING AMPLITUDE-RESPONSIVE CONTROL MEANS FOR DELIVERING A CONTROL SIGNAL WHICH IS RESPONSIVE TO AN ALTERNATING CURRENT SIGNAL; SAID CONTROL MEANS COUPLED TO SAID POTENTIAL SENSING MEANS AND TO SAID MOTOR CIRCUIT FOR OBTAINING THEREFROM AN ALTERNATING CURRENT SIGNAL COMPRISING THE DIFFERENCE IN ALTERNATING CURRENT POTENTIAL EXISTING BETWEEN A POINT AT SAID POTENTIAL SENSING MEANS AND A POINT AT SAID MOTOR CIRCUIT;