Typical circuit for welding equipment shown on the following circuit diagram. Turn on delay can be controlled accurately with Potentiometer P2. We can discharge C1 at each line zero voltage using DB1 diode bridge and R6-R7 resistors. The voltage charge will be reset at each new half line cycle and the turn-on delay will be maintained the same.

Through both potentiometers, the Transil reduces power dissipation. Here’s the circuit diagram:
Pulse train triggering circuit circuit schematic

Note: Transil is a transient voltage suppression diode trademarked by STMicroelectronics [Source: STMicroelectronics Application Note]