Hi.
>
> Sorry Trevor, but that is for a DIRECT current circuit.
>
> We are talking about the current draw on the
> input to the computer -- the ALTERNATING current (AC).
>
> I finally had some time to look up the formula....
>
> As you can see, AC circuit analysis is much more
> complex than DC circuits.
>
> Watttage = Voltage x Current x cosign of theta
>
> where theta is the phase shift between the voltage
> sine wave the leading OR lagging current sine wave.
>
> The phase shift is created by the combination of the
> inductance, resistance, and capacitance of the load (the PC).
>
> Jim Meagher

        95% correct, but the PC as seen from the AC side is not
a linear system since the first components found are the rectifying
diodes (and forward the switching supply, although being high frequency
should not add much theoretical complication), so there is more than
inductors, resistors and capacitors (although approximating the PC
as a resistor, and hence forgetting phase shift, is probably a good
approximation). This makes the current drawn from the AC supply a very
complicated thing, probably consisting in brief peaks at the AC voltage
peaks, so many harmonics. And what if the disk stops if having power
management? Then the peaks are shorter, so more harmonics.
        Perhaps someone on the list with a mainframe can provide info
on the reactive power compensation of his installation, or if someone
has observed the AC current into his PC with an oscilloscope and
a magnetic current translator.

> > Wattage is easy, it's simply Voltage multiplied by current so 110 volts
> > x 2 amps =220 watts or roughly 1 kilowatt hour for every 4.5 hours your
> > machine is on. This does not count the Monitor power consumption!
> >
> > Trevor Gibbs
> >
************************************
Javier Vizcaino. Ability Electronics. [log in to unmask]
  Starting point:        (-1)^(-1) = -1
  Applying logarithms: (-1)*ln(-1) = ln(-1)
  Since ln(-1) <> 0, dividing:  -1 = 1     (ln(-1) is complex, but exists)