I moved to an area/building where there are quite some problems with the wall-power supply. Primaraly I would like to protect my computers, secondary I would like have some affordable UPS for some of them.
A 90% efficient 1000W UPS for example, fully loaded, will consume 100W of power continuously.
quote from page 11
during the time that the power is ok, because they are constantly doing a power conversion subjected to loss.
There are some quite affordable "Line-Interactive" UPS around (which dont have much additional power consumption) but most of those have modified sine output, which appear to be dangerous for PCs with active pfc.
it's safe to use a non sine wave UPS in the US, or any other country where the line power is 120VAC ...... But I also tried to make another important point, it is ONLY safe if you are using a APFC PSU, this is because then there is only ONE input capacitor and it will be rated at 450VAC If you are using a Passive PFC or non PFC PSU you will have TWO capacitors, and a selector switch for 120VAC or 240VAC operation These capacitors will be rated for only 200VAC EACH In a country where the line power is 120VAC only ONE of the capacitors will be used But the square wave voltage will in the US be 470VAC/2=235VAC So that's why you need a APFC PSU, APFC PSU=450V capacitor Passive or non PFC PSU operated at 120VAC = 200VAC capacitor, too little for 235VAC square wave
The explanation behind the danger was based on some oscilloscope readings the output of such UPS, which contain besides quite blocky, quite high peaks at the block edges, that may kill some caps.
A general discussion on the topic of UPS and dangers to active pfc is interesting and can be found on many places, without a clear consensus (at least I didn't find it). So some clarification on that topic could be of interest, because conclusions seem controversial.
But at this point my main question is, if putting a voltage regulator behind such as "modified sine" ups, could prevent the damage by such peaks to PSUs with active pfc?