UPS and servers : simulated sine wave good?

Submitted ⁨⁨1⁩ ⁨year⁩ ago⁩ by ⁨foremanguy92_@lemmy.ml⁩ to ⁨askelectronics@discuss.tchncs.de⁩

cross-posted from: lemmy.ml/post/24328274

Hey I need your help.

Recently I bought a Riello NPW 2000 that output a “pseudo-sinusoidal” wave when running on battery the fact is that I read on the web that modern could do like it.
Mostly right as I found that my server (poweredge t430) is not running good with it. When unplugging the power to test the UPS something it make the PC just power off and reboot, or it make the ups in safety mode (continuous beep).
Tried disabling the PFC in IDRAC settings, as far I haven’t noticed power off issues but only safety mode issues with the UPS…

If anyone has an idea… Thank you

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Max_P@lemmy.max-p.me ⁨1⁩ ⁨year⁩ ago
Reposting my answer from the original thread. Maybe a bit rough for AskElectronics but still gets the gist.

To kind of visually see it, I found this thread of some guy that took oscilloscope captures of the output of their UPS and they’re all pseudo-sines: …anandtech.com/…/so-i-bought-an-oscilloscope.2413…

As you can see, the power isn’t very smooth at all. It’s good enough for a lot of use cases and lower end power supplies, because they just shove that into a bridge rectifier and capacitors. Higher end power supplies have tighter margins, and are also more likely to have more safety features to protect the PC so they can get into protection mode and shut off. Because bad power can mean dips in power to the system which can cause calculation errors which is very undesirable especially in on a server. It probably also messes with power factor correction circuits, which is something cheap PSUs often cheap out on but a good high quality one would have and may shut down because of it.

As you can see in those images too, it spends a significant amount of time at 0V (no power, that’s at the middle of the screen) whereas the sine waves spends an infinitely short time at 0, it goes positive and then negative immediately. All the time spent at 0, you rely on big capacitors in the PSU to hold enough charge to make it to the next burst of power. With the sine wave they’d hold just long enough (we’re going down to 12V and 5V from 120/240V input, so the amount of time normally spent at or below ±12V is actually fairly short).

It’s technically the same average power, so most devices don’t really care. It really depends on the design of the particular unit, some can deal with some really bad power inputs and manage just fine and some will get damaged over long term use. Old linear ones with an AC transformer on the input in particular can be unhappy because of magnetic field saturation and other crazy inductor shenanigans.

Pure sine UPSes are better because they’re basically the same as what comes out of the wall outlet. Line interactive ones are even better because they’re ready to take over the moment power goes out and exactly at the same spot in the sine wave so the jitter isn’t quite as bad during the transition. Double conversion is the top tier because they always run off the battery, so there’s no interruption for the connected computer at all. Losing power just means the battery isn’t being charged/kept topped off from the wall anymore so it starts discharging.

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- foremanguy92_@lemmy.ml ⁨1⁩ ⁨year⁩ ago
  Thank you for replying again, I think I found the problem, the UPS is faulty…
  
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667@lemmy.radio ⁨1⁩ ⁨year⁩ ago
There are some devices which will protest under modified sine wave, and some which may even get damaged. I recently accepted the risk of using an msw inverter with some electronics and did not notice any issues, but I had read that the device would be fine with it.

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- cmnybo@discuss.tchncs.de ⁨1⁩ ⁨year⁩ ago
  Computer power supplies won’t be damaged by modified sine wave inverters. Be sure to test your power supply on the UPS when nothing important is running though. Some power supplies will shut down as soon as the UPS switches to battery.
  
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  - 667@lemmy.radio ⁨1⁩ ⁨year⁩ ago
    That’s my thought, that the power blip is basically too long, and why I suggest to OP to try a different UPS.
    
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- foremanguy92_@lemmy.ml ⁨1⁩ ⁨year⁩ ago
  Seen that dell server PSUs are not really friendly with mdw but when PFC disabled it should not pose problems… But here it does
  
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  - 667@lemmy.radio ⁨1⁩ ⁨year⁩ ago
    Well, might have to do some isolation tests if you can borrow a pure sine wave UPS and see if it makes a difference. Outside of that, the power blip might be too much for the power supply to handle or it trips up BIOS/mobo voltage sampling.
    
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