Control system for energizing a directcurrent load from an alternatingcurrent source

Claim 1

A CONTROL SYSTEM FOR ENERGIZING A DIRECT-CURRENT LOAD DEVICE FROM AN ALTERNATING-CURRENT SOURCE COMPRISING IN COMBINATION, AT LEAST ONE GAS DISCHARGE TUBE HAVING A PLATE-CATHODE CIRCUIT INCLUDING IN SERIES THEREWITH SAID LOAD DEVICE AND SAID ALTERNATING-CURRENT SOURCE, SAID TUBE BEING OF THE TYPE HAVING A CONTROL GRID HAVING A KNOWN GRID VOLTAGE FIRING CHARACTERISTIC INDICATIVE OF THE GRID VOLTAGE LEVEL REQUIRED TO FIRE SAID TUBE ON EACH POSITIVE HALF-CYCLE OF THE VOLTAGE APPLIED BETWEEN PLATE AND CATHODE FROM SAID ALTERNATING-CURRENT SOURCE, FIRST GRID INPUT VOLTAGE MEANS FOR APPLYING TO SAID GRID A FIRST VOLTAGE COMPONENT VARYING IN A POSITIVE DIRECTION ON EACH CYCLE OF POSITIVE PLATE VOLTAGE SO AS TO GRADUALLY APPROACH SAID FIRING VOLTAGE, A SECOND GRID INPUT VOLTAGE MEANS FOR SUPERIMPOSING UPON SAID FIRST VOLTAGE COMPONENT A SECOND VOLTAGE COMPONENT COMPRISING AN ALTERNATING VOLTAGE OF RELATIVELY HIGH FREQUENCY AS COMPARED TO THE FREQUENCY OF SAID ALTERNATING-CURRENT SOURCE, AND OVERLOAD CONTROL MEANS RESPONSIVE TO THE LEVEL OF CURRENT SAID PLATE-CATHODE CIRCUIT FOR REDUCING THE NORMAL AMPLITUDE OF THE VOLTAGE PROVIDED BY SAID SECOND GRID INPUT VOLTAGE MEANS TO A SUBSTANTIALLY LOWER VALUE WHEN SAID CURRENT EXCEEDS A PREDETERMINED VALUE, WHEREBY IN RESPONSE TO SAID CURRENT OVERLOAD SAID LAST-NAMED MEANS CAUSES SAID TUBE TO BECOME CONDUCTIVE AT A LATER POINT IN EACH POSITIVE HALFCYCLE OF PLATE VOLTAGE TO THEREBY REDUCE THE CURRENT IN SAID PLATE-CATHODE CIRCUIT.