> What they found was that there was a harmonic reaction, where two 
 > or more PFC power supplies would get in sync, trying to modify 
 > what each perceived as distortion in the incoming AC sin wave as 
 > it was delivered to the computer load. 
I was reading your message for the second time and need to clarify a point. 
My "UPSs" are really "standby power supplies" and are NOT running on the 
inverter 100% of the time like a true, "online UPS" does. I'd guess that 
there are very few of the latter, especially today, as they now have what's 
called "line interactive" units that will boost/buck the incoming power to 
keep it uniform until it goes completely out of bounds. They switch to 
battery power at that time.
--- FLAME v1.1
---------------