Re: UPS to VFD hardware hack

Doug,

You're on the right track for a UPS to VFD, but as already pointed
out your can find surplus VFD's for less than you can build one!

However, I am a long time "learn by doing" so by all means do mess
around with a UPS to see what you can get it to do. Yes,
the "reference frequency" is most likely generated by a small
microcontroller. So the software becomes the item to modify to give
a different frequency.

To get an idea of a LARGE VFD, take a look at the electric vehicle I
use to play with. http://www.austinev.org/evalbum/121.html
Notice the custom controller used to create the three phase. Yes, a
big (300V, 1000A) VFD controller! Most of what you see is a HEAT
SINK! I used the vehicle for some R&D after the original division
that built it was shut down. It is VERY easy to blow up some $500
IGBT's with a software mistake. With six of them at risk, it can get
expensive getting this all working! Still, add some huge fuses, some
heavy duty plexiglass for those occasional "bangs!" and go to town!

Most the work, and credit, goes to a bunch of ex-Motorolan's. The
drive system is documented by Richard Valentine in Motor Control
Electronics Handbook. Do a search on Amazon.com. Recommended reading
if you want to get a better understanding of the control electronics,
with some practical "hands on" background.

Cheers,

Tom Walter
Austin, TX

P.S. I close on the new house next week. 1.4 acre lot, so will be
starting on the new shop shortly. 30'x50' two story... finally enoug
room for all the metal working things! Yes, it is bigger than our
2500 sq ft house!

> > Has anyone got any intuition as to whether this might
> > be possible? Inexpensive UPS's are available up to
> > 1500 VA (approx 2 HP).
> >
> > Doug Fortune
> > http://www.cncKITS.com