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ELECTRODE WELDING AND GOUGING
AC as welding current
Mains power will normally be AC, and the simplest form of welding power sources are transformers that reduce the mains voltage and provide means for adjusting the amperage (welding current), still delivering AC to the welding arc. As the AC actually is zero each time it changes direction only electrodes specially developed for AC will be usable with welding transformers.
The pulsating effect of AC has proven to be especially dangerous to an operator in case of electric shock. Where burns are the main danger from an electric shock from DC, the AC pulses may in addition cause cramps and heart failure as the pulses affect the nervous system. Authorities in several countries have therefore issued special regulations and demands for open circuit voltage reducing equipment for welding power sources with AC output.
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The only welding application that requires AC as welding current is TIG welding of aluminium, as the back and forth flowing electrons serve the purpose of tearing up the unmelted oxide layer that forms on top of an aluminium melt pool. However, in onboard repair and maintenance welding the Wire Welding Process Gas Metal Arc Welding (GMAW) process is an alternative for aluminium welding which offers several advantages, and is done with DC.
DC as welding current
DC is by far the best suited and most commonly used current for welding processes. It is normally obtained through a welding power source
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(inverter or rectifier) that rectifies the AC from the mains supply to a DC of correct amperage and voltage for welding. To avoid the dangers the current pulses represent in cases of electric shock, several countries have issued regulations on how smooth the DC current shall be in order to be accepted as DC without requirements for open circuit voltage reducing devices. These requirements should be observed when installing welding equipment on board.
DC current, constant towards the positive (+) pole.
AC current cycling from one direction through zero to the opposite direction, 50 or 60 complete cycles per second.