Circuit arrangement for maintaining the torque of asynchronous motors constant

Claim 1

A CONTROL ARRANGEMENT COMPRISING, IN COMBINATION: AN ASYNCHRONOUS MOTOR; A SYNCHRONOUS GENERATOR FOR FEEDING A VOLTAGE OF VARIABLE FREQUENCY TO SAID MOTOR, SAID GENERATOR HAVING AN EXCITATION CIRCUIT WHICH CONTROLS THE OUTPUT VOLTAGE OF SAID GENERATOR; AND A CIRCUIT FOR FORMING THE RATIO UL/F (UL=THE VOLTAGE DROP ACROSS THE AIR GAP OF SAID MOTOR, AND F=FREQUENCY) AND MAINTAINING SAID RATIO AND THEREBY THE BREAK-DOWN TORQUE OF SAID MOTOR CONSTANT, SAID CIRCUIT INCLUDING A SERIES-CIRCUIT INCORPORATING AN OHMIC RESISTANCE AND AN INDUCTANCE WHICH IS LARGE IN COMPARISON WITH SAID OHMIC RESISTANCE, FIRST MEANS FOR APPLYING TO SAID SERIES-CIRCUIT A VOLTAGE COMPOSED OF A TRANSFORMED PHASE VOLTAGE OF SAID GENERATOR AND AN OHMIC VOLTAGE DROP WHICH IS PROPORTIONAL TO THE MOTOR CURRENT AND WHICH IS SUBTRACTED FROM SAID PHASE VOLTAGE, AND SECOND MEANS FOR APPLYING TO SAID EXCITATION CIRCUIT OF SAID GENERATOR A VOLTAGE WHICH IS A FUNCTION OF THE VOLTAGE ACROSS SAID OHMIC RESISTANCE.