I have been looking to buy a TIG welder. But a lot of the shop sites on the internet also advertise inverters. What's the difference apart from price and the fact that an AC TIG will weld ally, between a DC TIG welder, an Inverter and an AC / DC TIG ?
Inverter refers to the technology used to generate the arc. Old TIG machines all used transformers and were big and heavy but reliable.
Inverters use magic to generate the arc - full of electronics that do the job of transformers. They tend to work very well, and are very small and light, but tend not to last as long as a transformer based machine, especially when sourced from China. Most modern TIG welders are inverter based.
I've never seen an AC only tig, DC or AC/DC are the norm but someone else may know different. I don't understand how they work but from what I have read, transformers are more limited in the way they weld under AC only having up to 50hz frequency available for pulse and HF has to stay on whereas inverter has up to 300hz in some machines and square wave and do not need HF after the arc is initiated. Also there are Mosfet based inverters and IGBT which is all gibberish to me so you can get even more involved and confused. If you want to be able to pick it up and take it anywhere you need an inverter. Have a look at this and see what you can pick up to help you make a decision.