Herbert,

In a DC circuit, you are correct, Wattage and VoltAmps are the same.  But
with AC you must also account for any phase shift which reduces the
effective wattage.  The AC formula for power is P = V * I * cosign(theta).
(or something very similar....  it's been a long time since I fooled with
AC circuit analysis <grin>).  In a pure theoretical circuit, theta is -90
degrees which has a cosign of 1  But in actuality, the phase shift results
in a cosign of less than one.

Jim Meagher
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----- Original Message -----
From: Herbert Graf <[log in to unmask]>

>         I have a question about W and VA. I just purchased a UPS
(Uninterruptible
> Power Supply) that has a rating of 400VA and 250W, my question is why
are
> they not the same?

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