PC PSU efficiency.

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PC PSU efficiency.

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Hairyloon

Joined: 20 Nov 2008
Posts: 15425
Location: Today I are mostly being in Yorkshire.

Posted: Wed Jun 17, 15 8:36 am Post subject: PC PSU efficiency.

I've been wondering about using a PC power supply as a low voltage power source for various things and I am wondering how efficient they are or not.
I assume there has been enough of a drive to reduce energy consumption that they are fairly efficient when running a computer, but what if they are running a lesser load?

Logically, I am thinking that a bigger power supply will have bigger wires therefore less resistance and lower losses, OTOH, I'm not entirely sure how they actually work, so I'm not sure that is necessarily the case...

vegplot

Joined: 19 Apr 2007
Posts: 21301
Location: Bethesda, Gwynedd

Posted: Wed Jun 17, 15 9:13 am Post subject:
They're output will be closely matched to the load but not always the most efficient of devices as manufacturers don't really care about running costs for desktop PCs.

dpack

Joined: 02 Jul 2005
Posts: 46209
Location: yes

Posted: Wed Jun 17, 15 12:27 pm Post subject:
my largest one has its own fan which is a indication that it isnt very efficient if it needs a cooling system to rid it of "waste"heat. all transformers/ac to dc /smoothers etc have heat losses but some are better than others.

Hairyloon

Joined: 20 Nov 2008
Posts: 15425
Location: Today I are mostly being in Yorkshire.

Posted: Wed Jun 17, 15 2:10 pm Post subject:

dpack wrote:

my largest one has its own fan which is a indication that it isnt very efficient if it needs a cooling system to rid it of "waste"heat.

If it is a 500W PSU and it is 90% efficient, then at full power it has 50W to get rid of.
Stick your hand on a 50W light bulb if you can't imagine what 50W of heat is like...

dpack

Joined: 02 Jul 2005
Posts: 46209
Location: yes

Posted: Wed Jun 17, 15 3:42 pm Post subject:
iirc it is about 1250w and it can warm a well insulated room if rendering raw video or 32 track techno

Duane Dibbley

Joined: 12 Nov 2009
Posts: 95
Location: Between Newbury and Andover

Posted: Wed Jul 15, 15 10:33 am Post subject:
I would estimate that the efficiency would only be 75-80% on the standard PC PSU and this would decrease as the load is reduced (I sell Power Supplies for a living). They are usually based around old technology due to cost and production life is 20+ years. We now have PSUs that are 94% efficient (with and without fans) so they are available but not in the PC PSU field.

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