Controlled rectifier current limit for d. c. motor

Claim 1

A CONTROL CIRCUIT FOR SUPPLYING CURRENT FROM AN ALTERNATING CURRENT SOURCE TO A DIRECT CURRENT MOTOR ARMATURE COMPRISING A UNIDIRECTIONAL CURRENT CONTROL DEVICE HAVING A MAIN CURRENT PATH AND A CONTROL ELECTRODE, MEANS COUPLING SAID MAIN CURRENT PATH AND SAID ARMATURE IN SERIES AND TO SAID ALTERNATING CURRENT SOURCE, A SOURCE OF UNIDIRECTIONAL CONTROL VOLTAGE, GAT ING MEANS FOR COUPLING SAID SOURCE OF CONTROL VOLTAGE TO SAID CONTROL ELECTRODE IN RESPONSE TO FIRST AND SECOND SIGNALS HAVING RESPECTIVE PREDETERMINED MAGNITUDES AND POLARITIES, GENERATING MEANS FOR GENERATING SAID FIRST SIGNAL, SAID FIRST SIGNAL HAVING A VARYING MAGNITUDE AND HAVING A PERIOD SUBSTANTIALLY EQUAL TO THE PERIOD OF SAID ALTERNATING CURRENT SOURCE BUT HAVING A PHASE SHIFTED IN ONE DIRECTION RELATIVE TO THE PHASE OF SAID ALTERNATING CURRENT SOURCE, MEANS COUPLED TO SAID ARMATURE AND TO SAID GENERATING MEANS FOR DERIVING A VOLTAGE INDICATIVE OF THE BACK ELECTROMOTIVE FORCE OF SAID ARMATURE AND FOR BIASING SAID FIRST SIGNAL THEREWITH, MEANS COUPLING SAID BIASED FIRST SINGAL TO SAID GATING MEANS, GENERATING MEANS FOR GENERATING OF SAID SECOND SIGNAL, SAID SECOND SIGNAL HAVING A VARYING MAGNITUDE, CONTROL MEANS COUPLED TO THE SECOND SIGNAL GENERATING MEANS FOR BIASED SAID SECOND SIGNAL IN ACCORDANCE WITH A DESIRED MOTOR SPEED, AND MEANS COUPLING SAID BIASED SECOND SIGNAL TO SAID GATING MEANS.