Hi, When your UPS is rated in VA's (and most are) you have to calculate with connected VA's too. In other words, when your non PF corrected computer power supply is 200Wmax and it's PF is 0.7 (average value for offline switchers), you have to calculate with 200W/0.7 = 286VA. So this will mean a maximum of 10 computers. When you work with active PF corrected PC power supplies (not very common yet), you can calculate with 200W/0.99 = 202VA resulting in a maximum of 14 computers. Please note that you always need to leave some power headroom when calculating needed UPS power. Or you must be sure that not all computers are drawing 200W or are not always operating at the same time. The large current crest factors of these mean offline switchers, could trip some kind of UPS current limit mechanism when working on the edge of UPS rated power. Daniel... ----- Original Message ----- From: "Micro Eng" To: Sent: Friday, December 07, 2001 6:46 PM Subject: [EE]: UPS's, powerfactors, and computers > ok...smart folks... > > You have a 200Watt (as rated by the manufacture) powersupply for your > computer. UPS's come in various sizes, say a 3KVa, so thats 3000 VA of > power. But its rated for pure resistive circuits. Backed off for a power > factor correction of .7 roughly, you get 2000 watts of power avaiable to > your devices. Now, do you account for the power factor for the power supply > against the 2000 watts? ie...200 watts is PF corrected to around 280 watts. > So does that mean that you can hook up only 7 computers? Or do you use the > non PF of 200 watts and lets you hook up 10 computers. Or do you use the PF > of 280 against the non corrected UPS value of 3000 watts? None of them seem > to add up the same. I believe that you use the PF of the UPS and the non PF > of the power supply? Need to figure this out rather soon. > > thanks a bunch > > > _________________________________________________________________ > Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp > > -- > http://www.piclist.com hint: To leave the PICList > mailto:piclist-unsubscribe-request@mitvma.mit.edu > > -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu