Re: [pvusers] True Sine Wave v. Mod Sine Wave

["Scott Willing" <willing@mb.sympatico.ca>]

Vis-a-vis efficient mod sq. wv. inverters essentially "moving 
inefficiency out of the inverter and into the device" -- that's an 
excellent point.

One tiny quibble - every PC I've ever owned, used or seen, including 
my laptops, had a switching power supply. Switchers do not have 
transformers in the 50~60Hz end of things and within reason do not 
"care" how pretty the input waveform is, or is not.

Incidently, when I bought a second rechargeable drill recently, I was 
pleased to find that Makita has changed over to switch-mode chargers. 
The charger for the old one is a weighty 60Hz transformer-based thing 
that buzzes and heats up on the mod sq. wv. power, but the new one is 
light-weight, and runs cool and silent thanks to the absence of a low-
frequency transformer.

-=s

On 24 Jul 2002 at 11:26, Dan Metcalf wrote:

> 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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