In general, when sizing a generator to run a welder, you need to significantly over-spec the generator. This is because a welder pulls a large amount of current just as the arc is struck, and this inrush can exceed the generator's capabilities. What happens is that the arc voltage drops and the arc goes out. The rod sticks, etc... Meanwhile you're running your welder at brown-out voltages and your generator is not going to be happy with you either.

By way of example, a Lincoln buzz-box 225 will draw about 5000-6000 watts at max output, but Lincoln recommends no less than a 15,000 watt generator to run it off of. That gives us an approximate ratio of 3:1 for generator size to welder inrush current. The PA160-STH pulls 30 amps max inrush, so that would suggest you'd want around 90 amps of generator capacity, which, at 220 volts equals around 20 kW.

Realistically, I think that Lincoln's 3:1 ratio is a little bit careful, and you could probably get away with less, especially with a quality generator. The Vantage 400 is rated at 11 kW continuous. This is about 1.6 times the PA 160's inrush current. I'm not sure I would feel good about running the PA160-STH off of that generator.