[pvusers] True Sine Wave v. Mod Sine Wave

["Dan Metcalf" <dan@metcalfs.com>]

I can't comment on the Powerstar, but I can tell you that for a little more
$ you could have an Exeltech XP1100 (1100 watt) inverter that will run
everything beautifully and without the buzz you heard in the ceiling fan.
I've seen it online for $700-$800.  (For those asking how noisy/quiet it is
I found the numbers: Audible Noise: Less than 45dbA when fan is running,
which is not that often for me)

The real theory with pure sine wave inverters is that although they are
listed to be less efficient at the inverter they are much more efficient at
the appliance.  The noise that you are hearing from the ceiling fan means
that it's working harder, using more electricity, creating more heat in its
operations.  Any appliance with a motor will run smoother, quieter and more
efficient with actual sine wave that it was designed for, which includes
loads like fans, refrigerators, kitchen appliances, ...  If you had the
systems to compare you'd probably also notice that wall plug transformers
run hotter too.  Other than humming or picture interference on TVs I'm not
sure what the efficiency issue might be there.  PC's are usually okay since
they run off of a transformer, but the transformer will run hotter.  CRT
monitors would probably be the same as any TV, some risk of interfering
lines and such.  All in all they true sine wave inverters give you more bang
for the buck in my opinion.

Depending on the sine wave form - how many steps it has, how close is the
wave form to an actual sine wave, you might see some real improvements in
performance by switching to a true sine wave unit like the Exeltech.  You
could then keep the Powerstar for a good reliable backup inverter.

I'm not affiliated with Exeltech, just a really satisfied customer!

Dan Metcalf
dan@metcalfs.com
http://www.metcalfs.com
The Sun!  Your source of energy for 5 billion years!
  Free while supplies last!


----- Original Message -----
From: "Jim La Joie" <jimjola@cts.com>
To: <pvusers@crest.org>
Sent: Wednesday, July 24, 2002 5:57 AM
Subject: [pvusers] Powerstar inverters and reliability


> I built my own PV system and used a PowerStar 1300 watt inverter. It ran
> everything fine (a little buzz in the ceiling fan) for 17 months then
> failed. It is being repaired as I write.
> When it did fail it took out a couple of AC adapters that run the phone
and
> my kids stereo.
> Does anyone have experience with the PowerStar? Is 17 months the average
> reliability? Do inverter failures usually harm downstream equipment? What
> can be done to protect against same?
> With good operating experience from a modified sine wave inverter, I am
not
> convinced that the pure sine wave is worth the money. Would like to hear
> thoughts on that.
> Also, who makes a reliable modified sine wave inverter.
> Thanks to all.
>
>
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