Closed loop motor control

Claim 1

A SPEED CONTROL SYSTEM FOR A FREQUENCY RESPONSIVE MOTOR, SAID MOTOR BEING A THREE PHASE INDUCTION MOTOR, THE SPEED OF WHICH VARIES WITH THE FREQUENCY OF THE APPLIED POWER, SAID SYSTEM COMPRISING: MEANS GENERATING A SIGNAL HAVING A FREQUENCY WHICH IS DEPENDENT ON THE ROTATIONAL SPEED OF SAID MOTOR COUPLED TO SAID MOTOR, SAID SIGNAL GENERATING MEANS HAVING AN OUTPUT; A STANDARD FREQUENCY SOURCE HAVING AN OUTPUT; COMPARATOR MEANS FOR COMPARING THE SIGNAL PRODUCED BY THE STANDARD FREQUENCY SOURCE WITH THE SIGNAL GENERATED BY SAID SIGNAL GENERATING MEANS, SAID COMPARATOR MEANS HAVING A PAIR OF INPUTS AND AN OUTPUT, AND SAID COMPARATOR MEANS PRODUCING A DIRECT CURRENT VOLTAGE SIGNAL WHICH IS INDICATIVE OF THE CHANGE OF THE SPEED OF SAID THREE PHASE MOTOR, SAID OUTPUT OF SAID STANDARD FREQUENCY SOURCE BEING CONNECTED TO ONE OF SAID COMPARATOR INPUTS, SAID OUTPUT OF SAID SIGNAL GENERATING MEANS CONNECTED TO THE OTHER ONE OF SAID INPUTS; FILTER MEANS FOR ELIMINATING THE UNWANTED ALTERNATING CURRENT COMPONENTS WHICH MAY BE PRESENT IN THE OUTPUT OF SAID COMPACTOR MEANS, SAID FILTER MEANS HAVING AN OUTPUT AND AN INPUT CONNECTED TO SAID COMPARATOR OUTPUT; VOLTAGE CONTROLLED OSCILLATOR MEANS FOR GENERATING A THREE PHASE ALTERNATING CURRENT VOLTAGE WHOSE FREQUENCY IS DEPENDENT ON THE VALVE OF A DIRECT CURRENT VOLTAGE SAID THREE PHASE GENERATING MEANS HAVING AN OUTPUT AND AN INPUT CONNECTED TO THE OUTPUT OF SAID FILTER MEANS, SAID OUTPUT OF SAID THREE PHASE GENERATING MEANS CONNECTED TO SAID MOTOR;