Flux cored arc welding required a rectifier-type DC constant voltage power source. These are made by Miller, Hobart, Lincoln, and everyone else. Inverters are suitable, but these are more expensive and there is no technical advantage other than light weight. Flux core is very tolerant of low-quality DC than other processes. For small diameter wires (up to 1.2mm or 0.045", you can use a source rated at 300A (100% duty cycle). For 1/16" (a very common size for general work), you will need a 450A or better machine. I don't recommend anything bigger than 1/16", except for a few specialized applications and some machine/automatic welding.
Gord
I recently purchased 3 Miller S32P cont / gas wirefeeder machines. These machines are wirefeeders only and a source would still be required. A standard MIG setup could be used with a changeout of the rollers.
In this case i think the Lincoln machines are the best .we are using these machines for more than 3 years hard working condition but they do not need to a very serious repair