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XPS 8950, issues with cheap UPS?

Does the XPS 8950 have any issues with cheap UPS? It has been a while since I had a desktop, but the last 2 Dells I had (10-15 years ago) were VERY fussy about the UPS. A cheap (still APC though) square-wave or stepped UPS would cause the computer to crash when the UPS inverter kicked in.

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4 Beryllium

I don't think the UPS'es are 'cheap'.

There are TWO types, AVR and PFC.

This should explain the 2 types, https://www.custompcreview.com/reviews/cyberpower-cp1500-avr-intelligent-lcd-cp1500-pfc-sinewave-ups.... For as long as I can remember, Dell's required PFC UPS's (as do many others). They will react faster I guess?

It is the AVR that the Dell's (have needed them since the XPS8500 from 2012) don't work with., Yes, the AVR models are cheaper.

This Dell article, https://www.dell.com/support/kbdoc/en-us/000155960/what-are-the-different-types-of-power-supplies-te... , appears to provide the reason, their PSU's are switching, not sine wave PSU's. AVR are sine wave, PFC as pulse.

I've been using PFC's since I don't know when, easily 2000 on electronic devices and PC''s. Matter of fact, I accidentally bought an AVR and didn't realize it until we lost power, and then looked at the unit. That now is connected to out Modem and Router (works fine).



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Irv S.


I am surprised this is still an issue!  On one of the Dells (old Inspiron 530), I replaced the power-supply with a name-brand, and the problem went away.

I remember it had something to do with how quickly the inverter cut-in when the power went out (not the wave-form), but when I last researched this 10 years ago, I thought power-supply manufacturers had corrected for this problem.


Just looked: guess it is still an issue. https://forums.tomshardware.com/threads/active-pfc-power-supply-with-simulated-sine-wave-psu-non-pur...

I was trying to avoid getting another pure-sine UPS...

8 Platinum

I have only been buying APC UPS-Units for 30 years. While all but one (recent) one is non-Sinewave ... their approximation seems to be very good.

Even the small/inexpensive ones (around 500-size and no AVR) worked fine for ANY MAKE computer or home theater component I tried on it. 

For the past 13 years, I've only been buying the black (upright) APC with LCD and AVR in the 1000-1500 range. In fact, I still have two working XS-1500's from 2010. 

Since the price is about the same now, I finally tried/bought a UPS Pro 1350 Sinewave for my projector. Works fine. After 4 years, looks like it's battery-pack has gone bad (that is normal life).

Actually, I have 2 units down at the moment ... I think one just needs a battery-pack and the other is giving me a random "clamping error" (not sure what that one needs or if it's even repairable). 

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That link is from 2018. Did you read it fully? "Simple, every PSU that has 80+ certification has Active PFC." and other newer classifications. You require a PFC USP.

I am not sure what your definition is of 'cheap' either?

AVR's are generally cheaper than PFC's though, but not by a significant amount?

Depending on configuration, the size of the UPS does effect price. Also 'what' you want out of it? I've got an APC, 3 Cyberpower's, one being and AVR.

ALL perform the same, with the AVR not on a PC. Major differences, the APC offer up more than 2x the same size unit. Due to the cost of the APC and its battery size. The 2 Cyberpower PFC's are on 2 different XPS's, and one has more in it, in terms of a bigger (power draw) video card and monitor. This is what I get on my CP1000PFCLCD (Around $170 USD) depending where you buy it:


The estimated time will fluctuate as low as 35 minutes to as high as 50 minutes at idle. More than enough time to finish what I'm doing. The lower powered XPS will get over 64 minutes, and the large APC will do 1 1/2 hours. These are all approximate though and are usually less.

The bottom line is that PFC's are required. Maybe more expensive AVR units can produce the signal that a PFC PSU requires? I don't know? Not sure what you are calling 'cheap' UPS's either.

I guess it also depends on where you live if you might even need one? Having lived in Central TX which seemed to be the Thunderstorm Capital of the US, we'd have frequent small drops of the power during some storms. Now in Fl., the problem is hurricanes and high power usage (unusual cold and high temps) and power can drop for second or be out for a period of time with those nature events.

Cyberpower costs between an AVR and PFC unit is not significant to the cost of the unit with AVR being cheaper. The PFC 1000VA (600W) unit list for $180 USD and can be cheaper bought from stores. It is $70 more for the next size up, but probably could even double the uptime?



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Irv S.


I am confused by the acronym AVR (Automatic Voltage Regulation).  The APS SmartUPS has it: https://www.amazon.com/APC-SmartConnect-Interactive-Uninterruptible-SMC1500C/dp/B078D6KZ98/ref=sr_1_...

Are the posts above suggesting AVR in a UPS is bad?

BTW, re: "cheap" (as compared with a SmartUPS), I mean something like this: https://www.amazon.com/APC-Battery-Protector-Back-UPS-BE600M1/dp/B01FWAZEIU/ref=sr_1_3?crid=3QAKUOUF...

Sorry for being dense...

2 Bronze
2 Bronze

My understanding from 10 years ago (subject to aging brain-cells) was that the issue was due to the new (at the time) PFC power supplies.  Here's the old article that makes me think PFC power supplies are the problem, and "I need a SmartUPS (or CyberPower equivalent)": 




OK, let's try and work on some points....

Cheap - well, let us change that to cost and performance then.

Cost goes up as does capability of the unit. That cheap one, it is only a 330W unit. Hardly enough to handle a PC with a 350W PSU. The 850VA on that page will work for a 450W PSU. Closer to what you really need, but it is $50 more. You have to match the power out to the PSU power rating. Otherwise it may not work.

PFC is the type of waveform. PSU's of late have the requirement for that type. Instant voltage vs. a waveform that transits more slowly. Later devices all are Star Complaint one, and those require for the most part PFC units... has nothing to do with cost although PFC usually costs more than AVR.

Cheap isn't the real word to use, but low powered is better.

In some cases, at I've show above, and I have an 8940SE with a 500W PSU, my idle draw appears to be under 150W's. However, I can push past 400 with some serious gaming.

More capability is better than less.


I am a Dell TechExpert. I am not a Dell employee. I enjoy using my free time to help the community. If you find my posts useful, you can thank me by clicking on Kudos!


Irv S.

2 Bronze
2 Bronze

Many thanks to all for helping me understand the technology these days!

I am not a fan of the PFC designs these days (which seem to have arisen from laws/regs re: energy efficiency), but at least I understand enough to make a purchasing decision.

I almost miss the days of full-wave bridge-rectifiers, massive transformers and massive caps!  Or at least pre-PFC switched power-supplies...

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