On (21 Oct 97) Jim Dunmyer wrote to Day Brown...
 JD> Most inexpensive inverters are square wave and cause excessive
 JD> heating in transformer-type power supplies. This includes the
 JD> 'wall wart' type of outfits. Most computers use switching
 JD> power supplies, and those are not bothered by square waves.
 JD> There are 2 other kinds of inverters: full sine wave and
 JD> 'modified sine wave'. The latter is supposedly OK for most all
 JD> applications, yet is much more efficient than the full sine
 JD> wave units. I don't know about regular power inverters, but my
 JD> standby UPSs here are full sine-wave and run about 60%
 JD> efficiency. That gives up a lot of solar and battery power!
Jim,
We just used Trace Engineering's classroom for Solar Energy
International's Photovoltaic Design and Installation workshop. So
I've been hanging around inverter engineer's for a week, and I start
to get a little bit of what they are doing.
Their sine wave inverters are slightly less efficient than their
modified square wave (marketing calls them modified sine wave)
inverters, but NOT 60%. The efficiency curve on the SW4024 never
goes below 85%.
The modified square wave inverters are somewhat better, as I recall,
but an interesting note is that even the (most) loads that run on
the modified square run more efficiently - cooler, quieter, more
powerfully - on the sine wave. The efficiency curves don't measure
this change in performance.
We've been running a Trace 2024 modified square for about 12 years
now. It's a great machine! We've thrown lots at it and it keeps on
going. The only thing that had trouble with it is our copier.
There's a handful of loads that don't like modified square, but most
can eat it fine.
I wish you could have been there for the full tour of Trace's plant!
You would have understood more than I did. These people make high
quality stuff. They weren't happy with the transformers they could
buy, so they make their own.
Take care,
                        Ian
... Pi R Squared? No. Pie R round, Cornbread R square!                        
 
... In the computer world, state of the art means you're all set for a few
months, until the art gets ahead of you.
--- PPoint 1.96
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