-----Original Message-----
From: Michel Jullian <[EMAIL PROTECTED]>
To: [email protected]
Sent: Wed, 7 Jun 2006 18:28:40 +0200
Subject: Re: Battery shapes
Terry allow me to disagree. I understand the UPS manufacturers rating
game, I
have played it myself, but it is not misleading in fact, it is not even
a little
cheating as you imply: if the 15 kW UPS you mention has to spit out 15
kW, it
_will do it_ of course, and if it's load has a power factor of 0.75 as
is quite
common, the rms current will _actually be 167 A_ (15000/(120*0.75)), so
it will
_really_ be outputting 167*120=20 kVA. And the wires will heat up as if
the 167A
were real, which they are.
The UPS rating only misleads the dudes who think that Pavg=Urms*Irms,
and those
deserve to be misled anyway ;)
Controversy solved?
Michel
P.S. As for the UPS's IGBTs or Mosfets, they often paradoxically prefer
this
kind of load (rectifier+filter, PF=0.6 to 0.8) to a purely resistive
load
drawing the same kW. Mine did in any case, as such loads only drew
current when
they were saturated :)
<><><><><><>
You're most welcome to disagree; however shifting the phase between the
voltage and the current does not contribute to ohmic heating of the
branch conductor.
Terry
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