Speed control system for polyphase induction motors

Claim 1

A SPEED CONTROL CIRCUIT FOR POLYPHASE INDUCTION MOTORS COMPRISING; A PLURALITY OF TERMINALS FOR THE APPLICATION OF POLYPHASE ALTERNATING CURRENT POWER, A PLURALITY OF STATOR WINDINGS, ONE FOR EACH PHASE, IN THE MOTOR, A PLURALITY OF VARIABLE IMPEDANCE CIRCUITS CONNECTED IN SERIES BETWEEN THE TERMINALS AND THE STATOR WINDINGS, EACH OF SAID VARIABLE IMPEDANCE CIRCUITS HAVING TWO SILICON CONTROLLED RECTIFIERS, EACH HAVING AN ANODE, A CATHODE, AND A CONTROL ELECTRODE, EACH IMPEDANCE CIRCUIT ALSO INCLUDING A VOLTAGE DIVIDER CIRCUIT COUPLED TO SAID CONTROL ELECTRODE AND CONNECTED IN SERIES WITH ONE OF SAID PAIR OF CONTACTS, TWO CONTROL CIRCUITS AND AT LEAST ONE PAIR OF CONTACTS CONNECTED TO THE CONTROL CIRCUITS, A RELAY INCLUDING A WINDING AND MEANS FOR ACTUATING SAID CONTACTS, SAID CONTROL CIRCUITS ADAPTED TO CHANGE THE RESISTANCE OF THE CONTROLLED RECTIFIERS WHEN THE CONTACTS ARE ACTUATED, AND AN OSCILLATING CIRCUIT CONNECTED TO SAID RELAY WINDING FOR GENERATING A SERIES OF PULSES WHICH ACTUATE THE CONTACTS AT A PREDETERMINED RATE.