wrote in message
oups.com...
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?

FWIW, I'm running an Hitachi L-100 VFD to power a 1 HP GE motor on my KO Lee
surface grinder and it runs fine and was easy to wire. The VFD was around
$250 (new) AIR, but to that I added a Hoffman enclosure, instrument relay
and diode, Square D fused disconnect, 220 VAC breaker (to the main CB box)
and a bit of wire and rigid and Liquitite conduit. That probably brought
the total to between $350 or $450. The point here is that there are often a
few (and sometimes many) gotchas in what it takes to get a job done.

The enclosure was to help keep grinding dust away from the VFD innards. The
instrument relay and diode was included so that the momentary on and off
switches on the grinder could be used to power it up and down, and the fused
disconnect because I don't like using a CB to power tools directly. A
contactor would probably have been better and may have eliminated the need
for the relay and dioide but I'm more comfortable specifying and installing
the disconnect box.

A rotary phase converter would probably have been cheaper but I was
attracted to the simplicity of the VFD, even though variable speed is likely
to be of little use on a surface grinder.

Mike