>> Robert Heller suggested that UPS architecture matters: >> AC->DC::DC Batteries::DC->AC >> Where input AC is electrically decoupled from output AC. >> Not many adverts for UPS's explain whether this is the case with their >> UPS. >> > > APC's SmartUPS line, Liebert, and Eaton Powerware are all true-sine wave UPS's, and do proper decoupling. Unfortunately, this kind > of data doesn't make for great ad copy, so it's left out, and you have to dig deep into datasheets to get that information. I pretty > much only use APC, and we have truly crap power here. Because of some heavy industry in the area, brownouts are common, and that'll > kill a PC power supply better than anything. I've pulled one 7 year old APC from a server closet where the lightning took the top of > the telephone pole OFF. THE UPS was fried, some of the breakers in the building were fused (!), but the servers were fine, outside > of the router that got zapped from the DSL modem. I beg to differ about APC. The accepted term for what Robert described is a "double conversion" or "online" UPS. APC's SmartUPS family is only available with the double conversion feature if you specify a "SmartUPS Online" model. The rest of the SmartUPS family use "Line Interactive" which runs on mains power until the voltage/current/frequency goes out of tolerance, at which point they cut over to battery. The Liebert GXT2/3 family which we use quite a bit of were, until recently, strictly double conversion. -- Drew "This started out as a hobby and spun horribly out of control." -Unknown