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UPS vs PSU [True and Myths]

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a b ) Power supply
April 10, 2011 3:28:21 PM

Some have argued that an UPS may in some cases demage the PSU.

I have read some articles on the internet, however I was not able to draw a final conclusion on the subject as the opinions vary quite a lot.

Basically there are 3 kind of waveform in the UPS:

1- square wave
2- quasi-sine wave pulse width modulated stepped rectangular waves
3- sine wave

Most agree that the best waveform is the sine wave, but UPS with this feature are a bit expensive to many, and some argue that it is not really necessary for most PCs users.

So my main concern is related to UPS with quasi-sine wave pulse width modulated stepped rectangular waves, which I have been using on my PC, which has a Corsair TX 850W.

Can an UPS (with quasi-sine wave pulse width modulated stepped rectangular waves) demage a PSU?

More about : ups psu true myths

a c 274 ) Power supply
April 10, 2011 3:54:49 PM

Apparently yes if your psu has Active PFC.
As far as i'm concerned it would have to be a worst case scenario though.
You'd have to be relying on the ups constantly and running the pc till the battery drains.
I have a simulated sine-wave ups and i'm not concerned in the least.
The ups has kicked in twice in the last year and a half for maybe a second or two each time before power was restored.
I think it's a none issue.
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a b ) Power supply
April 10, 2011 11:41:27 PM

jemm said:
Some have argued that an UPS may in some cases demage the PSU. ...
Basically there are 3 kind of waveform in the UPS:
1- square wave
2- quasi-sine wave pulse width modulated stepped rectangular waves
3- sine wave

Quasi sine waves and square wave outputs may even be harmful to small electric motors and power strip protectors. But all three are ideal perfect for all electronics. Because all electronics are so robust as to make any UPS output irrelevant.

Same reasons why most all 'so called' surges are made irrelevant by protection already inside electronics.

Anything a UPS might do to create a pure sine wave is completely undone by how electronic power supplies operate. Therefore a nearly $1000 UPS provides no useful function for so much more money. But are promoted by subjective rationalization.

As Davcon notes, a UPS output can be so dirty as to confuse PFC circuits inside some newer supplies. This is not and could not be destructive. Simply causes the power supply to see a loss of AC power. When a particularly 'dirty' UPS switches to battery, then a computer's supply may become confused.

That is significant. A UPS not in battery backup mode is some of the cleanest power seen by the load (ie computer). Often not understood when knowledge comes from hearsay. To discover if a UPS output is too dirty, unplug the UPS. Simulate a power failure. So that dirtiest power seen by any computer is generated by a UPS in battery backup mode. To learn if that 'dirty' power confuses a PFC circuit.
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a b ) Power supply
April 21, 2011 12:15:42 PM

Best answer selected by jemm.
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