IMac -- Compatible with UPS Square Wave Voltage

Question

I have been reading of the incompatibility of UPS square wave outputs of UPS devices and the new energy star 4 or 5 computers. The new iMac is energy star-5 compliant. The power supply output of a UPS will not work with new computers.
Does anyone have any information on this issue?

Answer 1

I’ve been trying to find the same answers for my 24”, intel,Core 2 Duo extrerme, 2.8GHXZ, iMac (mid 2007) that Apple Engineering says has Active Power Factor Correction power supply.
All I want from an UPS is decent time to unmount my external H.D., save my working data, and shut down the iMac properly. After the better part of two weeks I believeI have found the answer for my situation. Disclimer: I am not a tech nor experienced in electrical matters but just a guy who hung in there trying to make sense out of many conflicting bits of information. This is not meant to tell you what you should or should not do. Just what I believe I’ve found and what I have done about it
after talking to lots of tech people. Corrections/updates welcomed!
1. Apparently, there are some recent models of computers that have an updated power supply commonly called Power Factor Correction power supply (PFC), more specifically called Active Power Factor Correction Power Supply. As I understand it they were previously found mostly in the higher end of computers and not commonly found in the type that the average guy would use. Now Apple Engineering has told me via Apple Care that my 2007 iMac has an Active Power Factor Correction power (akaPFC) supply and that all wide range voltage supplies are PFC. I take that to also mean late model iMacs and most likely Mac Pros have this type of power supply.
Mine has it and it is a 2007 iMac, I’m not sure when they started using it in iMacs.
2. So what ? Well, if you tell an UPS mfg. your computer has an Active Power Factor Correction power supply or even if you drop the word “Active” (and use PFC) they will commonly say you need an UPS battery that sends electricity via a Pure Sine Wave to the computer. They are very costly units, easily $500 and up.
3. What is an Active Power Factor Correction power supply, aka Power Factor Correction supply (PFC)? Paraphrasing and editing a statement from a battery mfg support page: Although a computer power supply draws only a fraction of its full capacity during its steady state (normal) operation, Power Factor Correction (PFC) supplies have the potential to draw their full capacity ( which I assume is the stated watts on the computers data sheet), instantly when passing battery power to the computer’s Power Factor Correction power supply.
So what? well, the UPS may experience up to 8ms transfer time during this period which is just long enough to remove power from the computer’s Power Factor Correction supply which subjects the UPS to the maximum power draw of computer’s Power Factor Correction supply (PFC). This could result in a potential UPS overload or dropped power load ( computer restart, shut down ) because the UPS does not have the ability to furnish the amount of demanded power (watts).
4. I solved my problem of what kind and reasonable cost UPS would work with my Intel iMac after talking with APC , local Apple Authorized repair & CyperPower. First I determined the max watts draw of my iMac x 3 ( to allow sufficient excess watts when in an instant max watts demand from the Computer’s Active Power Factor Correction power supply ) and added the max watts draw of my external H.D. and FIOS Router to determine the total UPS watts that would be required to aid in the UPS selection process.
I purchased a CyberPower UPS model CP1500AVRLCD 900W , which successfully sent Simulated Sine Wave power just fine to my computer’s Active Power Factor Correction power supply when testing it two times. No need for costly Pure Sine Wave UPS. Cyberpower says this unit will work with the iMac but not work with the Mac “Tower” / Mac Pro and I suspect it has to due to the huge difference between them in maximum watts that can be instantly drawn when the Active Power Factor Correction power supply instantly demands the full watts power from the UPS.
APC UPS model BR 1200 (also a non pure Sine Wave UPS) is recommended by a local Apple Authorized Repair facility (vendor) to his customers as working with the current iMacs.
I personally think the difference in working and not working is getting the right amount of excess watts in the UPS, can’t think of any other reason it works. I really don’t care as long as it works.