Steve,
Thanks for this tech info. I don't much rely on the KVA rating of a UPS.
I use the actual load wattage documented. I suppose that my home's
electric meter does much this same calculation internally; and, for all
I know, perhaps the meter may be actually showing KVA(?).
Best,
Duncan
Steve Tomporowski wrote:
Duncan,
Thanks for the update. I had already noticed that the APC 1500VA UPS
was rated at 890 (or whatever) watts. Now Volt-Amperes, especially when
you are talking AC, does not equal watts because there is a phase angle
between the voltage and current. So the actual power is P =
Vrms*Irms*cos (theta), where cos (theta) is the phase angle between
current and voltage, e.g. the peaks of both do not occur at the same
time. This probably has something to do with the filtering in the UPS
because as soon as you put something frequency dependent in the circuit
like a cap or inductor/choke, the phase angle changes.
Steve
