low power factors are bad -- you pay for the higher VA, but are only using the lower watts to do actual work !!
I'm really surprised that USP doesn't have a PFC front end to bring everything back into line. Bob M. wrote: > > I have an APC SU2200 (SmartUPS, 2200VA) 3U tall, that I put new > batteries in a few months ago. So far it's just sitting, plugged in, > turned off, with no load. I got curious as to how much power it was > sucking out of the wall outlet, so I plugged the UPS into my > Kill-A-Watt device and plugged that into the wall. Here are the > numbers I observed: > > 122.2 Volts > 1.48 Amps > 31 Watts > 181 Volt-Amps > 0.17 Power Factor > > The values were identical with the unit turned on, also with no load. > The only thing running inside the UPS is the battery charger; the > inverter is completely bypassed and is not running. > > I then ran the UPS into a test cycle, again with no load, but this > time the inverter turned on and powered the load, thus disconnecting > itself from the commercial AC power. Surprisingly, there was still a > little bit of power being used, probably by the transformer and line > sampling circuit. Here are the readings I got during the self-test: > > 122.4 Volts > 0.09 Amps > 0 Watts > 11 Volt-Amps > 0.06 Power Factor > > As far as I know, the utility's kilowatt-hour meter on the side of my > house, which is a rotating aluminum-disc style, measures WATTS, not > Volt-Amps. Somehow APC has managed to get their charging circuit to > draw a lot of current while keeping the power factor and Wattage power > extremely low. I suspect it's highly capacitive. > > So here's where you all get to jump in. Is this UPS costing me a lot > just to keep the batteries charged (180 VA) or am I only being charged > for the wattage it draws? > > Bob M. > >
