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PSU's Power Factor?

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attack

Member
Joined
May 23, 2002
Do PSU's have a unity PF? If not anyone know what they are? (I'll assume if they all arn't unity they'll be some difference, but in general...)

Thanks
 

baru

Registered
Joined
Apr 10, 2003
Location
SoCal
Here I go off on something that I'm not completely sure about...If I'm completely wrong, for the love of all that's sacred, please correct me.

From what i get here

http://members.tripod.com/~masterslic/FAQ-2/22.html

and my other thread here

http://forum.oc-forums.com/vb/showthread.php?threadid=251061

it seems to me that you would be incredibly lucky to have a power factor of unity. I believe that the efficiency rating found on newegg for many of their power supplies would be ok to use. With a semi-randomly chosen 350W Fortron power supply, we see

http://www.newegg.com/app/ViewProdu...-104-966&catalog=58&manufactory=BROWSE&depa=1

that the efficiency is a minimum of 65%, typically 70% under full load (which is probably what most people here are at. If you're not... fold for team 32! :D) I want to just convert this to a power factor of 0.65-0.7, but that's probably not right.

The primary reason for my stating that the power supplies are not a power factor of unity is the fact that there are power factor correction power supplies. If there was nothing to correct, such things would probably not exist.

I would be interested to see some readings off of some of the forum member's rigs using a wattmeter, ammeter/voltmeter and the math in the first link. I'll try to take some measurements this weekend.

Another link on comparison of power supply efficiency:

http://www6.tomshardware.com/howto/20030609/power_supplies-02.html

What bothers me is the fact that the 450W Fortron with active PFC has the same efficiency as the non-PFC 350W psu. Is this just because power supplies lose efficiency as they become larger?

yes, i like giving links :D