Magnetic amplifier circuits, especially for arc-welding equipments

Claim 1

IN AN ARC WELDING SYSTEM SUPPLYING A DIRECT CURRENT OUTPUT THROUGH LOAD TERMINALS TO FORM A WELDING ARC; AN ALTERNATIVE CURRENT SOURCE; A FIRST TRANSFORMER HAVING A THREE-PHASE PRIMARY, SECONDARY WINDINGS AND RECTIFYING DEVICE THEREON TO SUPPLY A RECTIFIED OUTPUT; A MAGNETIC AMPLIFIER SUPPLYING SAID DIRECT CURRENT WELDING OUTPUT FROM SAID RECTIFIED OUTPUT, SAID MAGNETIC AMPLIFIER HAVING LOAD WINDINGS, CONTROL WINDINGS AND POLARIZATION WINDINGS; THE IMPROVEMENT COMPRISING A CIRCUIT, COMPRISING, IN COMBINATION, AT LEAST ONE GRID-CONTROLLED SOLID STATE THYRATRON WITH AN ANODE THEREIN SUPPLYING SAID CONTROL WINDINGS OF SAID MAGNETIC AMPLIFIER, AND A PHASE SHIFTING NETWORK HAVING A WINDING WITH A CENTRAL TAPING IN WHICH THE CURRENT IS IN PHASE WITH SAID ANODE OF SAID SOLID STATE THYRATRON, SAID WINDING OF SAID PHASE SHIFTING NETWORK FORMING PART OF A GROUP COMPRISING AN AUXILIARY TRANSFORMER AND AT LEAST ONE VARIABLE RESISTOR FOR VARYING THE PHASE ANGLE OF THE CURRENT SUPPLYING SAID GRID OF SAID SOLID STATE THYRATRON THROUGH AUXILIARY TRANSFORMER TO PROVIDE A RECTIFIED CONTROL CURRENT TO SAID CONTROL WINDINGS OF SAID MAG-