Arc welding transformer power controller circuit

Pulse-train triggering circuit

The schematic in  shows a typical power controller circuit for arc welding transformer. Potentiometer P2 is used for accurate control of the maximum turn-on delay. DB1 diode bridge and R6-R7 resistors are used to discharge C1 at each line zero voltage. This resets the voltage charge at each new half line cycle, and keeps the same turn-on delay. The Transil reduces power dissipation through both potentiometers.