EN setting like he said.
for those who dont understand AC welding. AC is alternating current, the machine’s arc switches from the tungsten + (welding torch) to work piece - very fast. The + (from torch to work) is what creates the puddle. The - (from work to torch) is what “lifts” the oxide layer of aluminum off the work. The better machines can adjust the % of how much - (EN or electrode neg.) it runs at. The more EN the more cleaning, but naturally the less penetration. So its a balance. The white shit around the sides of a aluminum weld bead is the cleaning action you can see after the fact. A MM or so of white shit around the weld bead is idea… any more is too much EN and wasted penetration. The downside to also cranking in a ton of EN, is even on inverter machines the tungsten will ball up more (transformers do this anyways, it just gets worse) and makes the arc not as stable. Also the more heat into the tungsten it can actually fail and fall off into the work.
lil ac welding 101 for yah