ELECTRIC ARC WELDING POWER SUPPLY

摘要

ELECTRIC ARC WELDING POWER SUPPLY A three phase electric arc welding power supply using SCR rectifiers for output control which has improved output characteristics, fault protection and current and voltage controls. The main power transformer is connected in a double wye with the neutral points interconnected by a pair of independent interphase inductances in series, the mid point forming one of the output terminals. Increased phaseback of the SCR's may be effected without the use of additional inductance in the output circuit. The fault protection circuit has a timecurrent trip curve closely approximating the time-current overload curve of the SCR's whereby the minimum size SCR's for a given maximum current output is obtained. The control circuit is fast responding and gives either: constant voltage output; or variable voltage, constant current output with both line voltage compensation and with increase of current when the arc is shorted and the arc voltage drops below a predetermined amount. Improved firing circuits for the main and pilot SCR's are provided.