Gary Coffman wrote:

Note that since VFDs above about 3 hp are not designed to be run from
1 ph power, you may need to modify them to work that way, as well as
also derating them. Usually this means defeating a phase loss detector
in the VFD which shuts it down when a missing input phase is detected.


I'm sure there are VFDs that have this feature, but I haven't run into
one yet.
I have run a number of VFDs from single phase, and never had any trouble
with it.

Defeating this circuit can be simple, difficult, or essentially impossible,
depending on the design of the particular VFD. You're somewhat on
your own here because you're using the VFD in a way for which it
wasn't designed.

Note also that high power VFDs, greater than about 3 hp, start getting
expensive. If you just need to make 3 ph from 1 ph power, a home made
rotary converter will be much less expensive in the higher power ranges.


New, straight from the distributor, yes, they are quite expensive. But,
new units that are last year's model or overstock are plentiful, and can be
found on eBay all the time.

I'm currently facing that dilemma. My new lathe is 7.5 hp 3 ph. That
means I'll need a 11.25 hp VFD to run it on single phase. Since that's
not a standard size, I have to go up to a 15 hp VFD. That's $929 from
Dealer's Electric. Then I have to hope I can fool its phase loss detector
into letting it run off of 1 ph power.


Well, you really don't need one that big, unless you really plan on
running the
lathe at full power for an extended time. 7.5 Hp is a lot!

Jon