I've done both, they both work well.

The two big issues from my viewpoint:
A VFD gives you variable speed, which can be a nice thing.
Only some VFD's will deal well with mechanical switching between the VFD
and the motor. This makes it a pain in the rear to have multiple
machines on a single VFD. RPC's have no such problem.

Steve

wrote:

I recently bought a 3 phase 1 HP surface grinder. My original intention
was to replace the motor with a single phase unit. But the motor on the
grinder is closely integrated with the tool itself. I suspect that it
would be VERY expensive to take that approach.

So I'm looking at putting 3-phase power into the garage instead. Since
my shop is in my garage, I doubt that I could get the power company to
put in 3-phase power for any reasonable price. So I'm looking at
alternatives.

I ruled out static phase converters almost immediately.

But the choice between a rotary phase converter and a variable
frequency drive unit (VFD) isn't nearly so obvious. Each has good and
bad points - making the selection very difficult.

So, I'm asking you to help me choose. If you currently have or
previously had both types of units in your shop, which type would you
pick to power a 1 HP grinder?