DIY TIG welder help

Discussion in 'General Electronics Chat' started by Drebank, May 17, 2009.

  1. Drebank

    Thread Starter New Member

    May 17, 2009
    I plan on converting a plain old 140A AC stick welder into a DC TIG welder with power regulation. Since I never dealt with such large currents, I need a little help.

    I got a powerful triac (supposedly 200A/1000V) and plan on using it in primary circuit of AC welder constant current transformer in a similar circuit like a light dimmer, with phase angle controlled by a microcontroller. Is there some problem in this setup I am not aware of, since the currents are rather large? I would turn the selector for maximum current (140A) and use the phase angle to control welding power and e.g. pulsed welding mode. Is this ok?

    In the secondary I would make a bridge rectifier with 4 powerful diodes and a hall effect current sensor to tell the microcontroller how much is cooking, do I need to add some very large capacitors after the diode bridge (since small ones have no effect on such large currents) or can do without them for TIG process (main interest is plain and stainless steel, not aluminum)?

    There is a large IGBT (400A/1200V) on my shelf, so a thought came to mind placing it between the negative electrode lead and ground to PWM control/shape welding current but I'm worried of voltage surges produced when chopping currents on the order of > 100A. Thanks in advance for all advice here, and also feel free to PM me with any tips.