MODERN ARC WELDING POWER SOURCESRecent advances in the field of solid state power electronics have helped to improve the status of welding power sources. With the development reliable high current thyristors (SCR's) and transistors many things are possible in the field of arc welding power sources. Universal power sources with selectable output characteristics are now available. With this type of equipment one can do SMAW, TIG & MIG welding and gouging all with a single power sources. A switch on the front panel selects the output characteristics required and the rectifier output is controlled by electronic circuits to give the desired output. Application of power transistors and thyristors in the field of welding power sources has produced new welding techniques like, pulsed TIG, pulsed spray MIG and synergic pulsed MIG welding. These techniques were not known previously and these were evolved as part of equipment development.