Bino,
I apologize. I was not aware that the 'power' industry seems to be shifting
to this new (well, new to me?) VA rating. I just got a white paper
(pdf) from
APC called, "Watts and Volt-Amps: Powerful Confusion". Seems to agree with
much of the link you shared.
It seems that my old 1970's-1990's viewpoint of power comprehension is
sadly prehistoric! LOL! Smarter now; even though I'm not sure how to use
all this new perspective.
However, I generally plan a UPS VA rating based on a 40% nominal wattage
load against the published UPS max. wattage. I realize this appears
wasteful,
but I've never had a UPS failure, equipment failure, and run my UPS's to
nominal battery failure (3-5yrs).
Smarter now! Thanks.
Duncan
On 08/02/2011 15:41, Bino Gopal wrote:
Hi Duncan,
Hehe it's not all about winning (well, unless you're
Charlie Sheen) but anyway it's interesting you say it's about kWh and
not kVA since you're one of those people that link I mentioned is
referencing-since you have that new digital 'smart' meter, the power
company is now going to probably try and charge you for VA use in the
future to encourage energy efficiency-so if you have and old AC unit
that only has a PF of .6, that will encourage you to get smart and
upgrade to a newer one with a higher PF...
Only speculation on my
part, but that is what I would expect since the power company has to
generate the VA but only gets to charge you for the watts...here's that
link again:
http://www.generatorguide.net/watt-acpower.html
Oh
and my point about the VA rating of a device really applies to UPS
sizing at this point! To use your example, it's exactly why a 1500VA
UPS can only supply 875 watts of real power, based on how UPS
manufacturers rated their UPS for PC computer loads...
Do me a favor Duncan, read this link and tell me if it makes sense or not:
http://www.power-solutions.com/watts-va.php
I
think it should and then you (just like me) will get the difference in
VA vs watt ratings for most UPS in the consumer-grade category!
HTH!
BINO
P.S.
Really, the takeaway from that last link is that UPS manufacturers have
been
overestimating/lying about their VA ratings for UPS for PC use to make
them sound
bigger, when it reality they can only handle much less, i.e. their watt
rating! Whereas with bigger UPS (but I don't know what constitutes
"big" in this case), their VA rating=watt rating...
Date: Tue, 2 Aug 2011 12:28:09 -0400
From: [email protected]
To: [email protected]
Subject: Re: [H] PFC (power factor corrected) PS for PCs?
Bino,
OK. You win! Yes the AC voltage you measure at the wall plug is 0.707
(rms) of the peak AC sinusoidal wave-form (169.731V) when viewed via an
o-scope. My comment was with regards to your concern about KWh and KVA
values. In your apartment you spend your dollars buying AC power
measured in Watts not KVA.
Yes, have read about these new digital 'smart' residential watt-meters.
I have one on my home now. And I fully expect that in the future (as my
AC Service provider completes it's 'Smart Grid' technology) I may see my
bill change based on 'time of day' power usage during peak demand
(system wide) situations.
Yes, it is confusing in the UPS calculation game. All of my UPS's are
rated at 1500KVA. Yet, they also will only supply a maximum output of
875 watts continuous.
I do not follow your points about 'VA' rating of a device. If it plugs
into your wall plug it is spec'd in watts.
My understanding about Power Factor and/or Power Factor Correction
technology is some form of quantifying electrical efficiency. IMHO. I
leave area to the those that understand. I do not. Yet I do agree that
our modern PSU's are very much more efficient AC to DC converters.
Sorry to interject skepticism into your search for truth.
Best,
Duncan
