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Power Supply Question

S

Snowbum

n00b
Joined
Feb 6, 2004
Messages
40
Could someone please tell me what PFC means when it comes to PSUs? I am trying to decide between the following two power supply units but I am not sure what the difference is. One says with active PFC and the other says N/A for the PFC. What is PFC? Are there different types of PFC?


Here is the one with PFC

http://www.newegg.com/app/ViewProdu...-153-010&catalog=58&manufactory=BROWSE&depa=0

Without

http://www.newegg.com/app/ViewProdu...-153-008&catalog=58&manufactory=BROWSE&depa=0

Which ever one I choose is going into a Thermaltake Silver Xaser V Damier Full V6000A. Is one of the power supply units better than the other for this case?

http://www.newegg.com/app/ViewProdu...1-133-124&catalog=7&manufactory=BROWSE&depa=0
 
I have a silentpower with PFC and one without PFC. I can't tell the difference, at least by stability of the rails. Both have been VERY consistant, even on highly OCed systems.

Oh, and from a review:
" What is Thermaltake Power Factor Correction (PFC).
It is to attempt to remove and compensate for the effect of leakage inductance that is lost from the output current. Non-PFC gives around 0.5~0.6 Power Frequency while Thermaltake Active PFC give a more efficient Power Frequency of 0.95~0.99."

Whatever that really means.
 
Originally posted by LabRat
Oh, and from a review:
" What is Thermaltake Power Factor Correction (PFC).
It is to attempt to remove and compensate for the effect of leakage inductance that is lost from the output current. Non-PFC gives around 0.5~0.6 Power Frequency while Thermaltake Active PFC give a more efficient Power Frequency of 0.95~0.99."

Whatever that really means.
Click to expand...

What that means, roughly is it makes the PSU act more like a 'simple' load on the AC line (ie a oven, or a toaster, a basic resistive load), a complex load (like your PSU) is a reactive load, with both capacitance and inductance, the result is, unlike in a simple resistive load, the currnent draw is not in 'sync' with the voltage wave. (ie a simple load, the current from AC will trail the Voltage wave in a nice uniform pattern, two sine waves moving together),
the current draw will varry fairly widely from the votlage wave,
and actual poiwer delviered to the supply is a function of
Volts RMS * Amps RMS * power factor
where power factor is cos(phase angle between Votlage wave and Amp wave)
the lower the power factor, the more power you have to deliver to the suppler to get the same effective (or real) power.

what good active PCF (all PSUs use some PCF, some use passive, active is more useful), does is increase the power factor (by reducing the pahse angle),
in this case from ~.5 to .95,
what that means is instead of needing ~700VA (volt amps, Volts RMS * Amps RMS) to get 350W (real power) to the Supply, you need only ~370VA.
 
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