not a inverter, a converter, a digital one at that, i think a 400A mig turns into about a 250A after the conversion, thats the penalty. a 400A mig is about 35v as is at the moment. if any of that makes sense. the makers of both my machines kemppi and miller say they have no problems with a digital converter, mind you both are out of warrenty now so maybe thats got something to do with it.