Question Can a PSU consume more power from the ups than it can provide?

Sep 18, 2019
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For example:
Can a 600w psu can draw 400w of power from a ups that is rated 650va 360w?
If it can will it damage the ups?
What will happen to ups if electricity goes off?
 

Lutfij

Titan
Moderator
Make and model of your PSU? Might want to list your specs like so:
CPU:
Motherboard:
Ram:
SSD/HDD:
GPU:
PSU:
Chassis:
OS:

Also the number on your UPS is to state the max power output by the UPS during battery backup, last I checked. Might want to mention the make and model of your UPS as well.
 
Reactions: zamorin_theNxt

jay32267

Champion
For example:
Can a 600w psu can draw 400w of power from a ups that is rated 650va 360w?
If it can will it damage the ups?
What will happen to ups if electricity goes off?
I think that if you try to get more power from a UPS than it can provide one of two things will happen.....either the voltage will drop or it will power down.
As far as damaging the UPS.....I doubt it.
 
Reactions: zamorin_theNxt
Sep 18, 2019
10
0
10
0
Make and model of your PSU? Might want to list your specs like so:
CPU:
Motherboard:
Ram:
SSD/HDD:
GPU:
PSU:
Chassis:
OS:

Also the number on your UPS is to state the max power output by the UPS during battery backup, last I checked. Might want to mention the make and model of your UPS as well.
I asked this question for clarification. I am no expert in computers 😁
Anyway thanks for helping out I think I get the answer.
 
For APC, if you load it up with greater than the rated capacity:

it works but beeps continuously when there is line power (until very severely overloaded in which case it shuts off). This is annoying enough to prevent you from using the UPS even if the PC is seldom loaded to 400w and the UPS would be sufficient most of the time when the PC is near idle.

the moment there is any power cut, the load is immediately dropped. This makes it worse than no UPS as otherwise your PSU may have enough hold-up time to ride out small power glitches.

there should be no damage to the UPS or PC, except anything cached but not yet written to disk will be lost, possibly causing data corruption.
 

antiglobal

Distinguished
Dec 18, 2011
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If the PSU is 80% efficient, and it is 600W rated, that means that under 100% load it will draw 750W from the UPS. But your computer components need to draw 600W to get full load. If it draws 400W from the PSU, the PSU will draw 500W from the UPS.

UPS power output of 650 VA is equal to 650 W if the power factor of the PSU is 1 (which is never). If you have a PSU with active PFC, the power factor should be close to 0.9, or to be safe let's say 0.8, which would mean 585 W or 520 W max power output of the UPS.
But if the PSU does not have active power factor correction, and the PF is 0,5 it means that the max output power of the UPS is half of the VA rating, 325 W.

If the max power draw of the UPS is exceded, the UPS should have protection, and nothing will happen to it, but the compter will freeze and/or shut down.
 

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