VFD's are rated for certain motors. So you might have a 2.2kw motor rating and such you will require either a 2.2kw VFD or higher but it's best to use the same rating. Now what I've been having issues with it my VFD has been nuisance tripping my RCD and thus now having a none RCD circuit wired in to my workshop to stop it due to the current load on startup. Also, go for a water cooled spindle, your ears will thank-you afterwards!

Rob