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Written by foremanguy on 2025-01-02 at 10:28

UPS and servers : simulated sine wave good?

https://lemmy.ml/post/24328274

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Written by yannic@lemmy.ca on 2025-01-02 at 10:57

I’m having difficulty understanding your post but you’re on the right track with Active PFC causing issues with UPSs.

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Written by foremanguy on 2025-01-02 at 11:02

I’ve modified my post, read it again see if you have a potential answer

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Written by TBi@lemmy.world on 2025-01-02 at 11:02

Some systems just need a pure sine wave UPS. Especially high grade server hardware. But test the UPS with other computers, it could just be faulty.

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Written by foremanguy on 2025-01-02 at 11:06

I only have a desktop computer but its supply is rated 80+ gold, so it has PFC (if I understand correctly)? Maybe I can disable it in the BIOS? (Going to try)

Already tried running different equipment on the UPS such as modem/router from my ISP or a simple home phone. None of them were having troubles with the UPS…

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Written by TBi@lemmy.world on 2025-01-02 at 11:10

PFC is in the power supply. The bios doesn’t control it. Only servers may have this control.

Try running some equipment that needs extra load from the UPS. TV? Gaming system?

Again could just be an issue with the UPS.

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Written by foremanguy on 2025-01-02 at 11:13

So it wouldn’t work with my PC?

Sorry I was talking about disabling the PFC with the dell Idrac, not the bios.

Going to try some heavy load on it.

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Written by user134450@feddit.org on 2025-01-02 at 11:23

How many PSUs are installed in the Poweredge server? In the manual it says it could be 1 or 2 and the power per PSU could be 1100W so if it is 2 * 1100W then that could explain why the UPS has problems with it.

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Written by foremanguy on 2025-01-02 at 11:43

Only one and it’s a 750 w one. The UPS has a capacity of 900w

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Written by SirEDCaLot@lemmy.today on 2025-01-02 at 11:34

I would return that UPS and for about the same price or not too much more you could get a cyberpower unit that puts out a real sine wave.

Obviously your server does not like Riello’s fake sine wave, so why not feed it the good stuff rather than trying to force it to eat garbage?

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Written by Max-P on 2025-01-02 at 12:00

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.

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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Written by foremanguy on 2025-01-02 at 12:55

I think the problem is the PSU of the server (and I think this normal, not a fault of it), will check further

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Written by magikmw@lemm.ee on 2025-01-02 at 13:04

This comment tought me more about PSUs and UPSs than my entire experience in IT in a very concise way. Good one.

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Written by Bakkoda on 2025-01-02 at 13:17

I would just not use anything but double conversation. Buy a refurb with new batteries and a solid warranty and don’t worry about it again.

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