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server psu's: do they have Active PFC?

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mab2

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hello all,

I have previous experience of converting ATX PSU's but for the next project I'd like something with a bit more 12v oomph, cheap, and active power-factor correction. But whilst ATX psu's generally advertise the fact that if they've got APFC, non of the server psu's labels I've looked at say one way or the other, although they tent to have a.c. inputs 100-240v - which is typical of APFC.

do they have APFC? and if some do & some don't, is there a way to find a cheap 2nd hand one with APFC.

specifically I was looking at a pair of dell poweredge 750's but would prefer not to take a gamble, and so far googling the part no. hasn't revealed the answer.

any advice or expertise would be appreciated before I spend my money. :)
thx
M
 
well it'll be converting power from a small hydro-generator; I'm using a standard atx psu for now but the poor PF (passive PFC) causes significant efficiency reduction in both the generator and transmission line c.f. a resistive load. Also the wide input voltage window of a typical APFC psu allows for easier connection to the generator who's output voltage can vary significantly, depending on available water and loading.

as I want to upgrade for more power I was going to use an APFC ATX, but then noticed the server PSU's were in the right power range anyway but am struggling to confirm the PFC type for sure.

Have found some for sale that are labelled PFC and are switchable between 120 / 240, but the 100-240v labelled ones don't say what PFC type they are.

worst comes to worst I can buy them and then Ill know, but if someone is familiar with server PSU's they could save me 'taking a gamble'.
 
It's usually more efficient (~2%) to run them at 240.
The newer servers have the ability to disable power factor correction to reduce power consumption when the system is in standby (S5) in the iDRAC Settings so it's something you might want to check as a option on the servers you get.
 
well I'm not running servers - I just want to use the PSU's and what they do in standby mode wouldn't matter - though for simplicity's sake I should probably avoid anything with too many settings/ control inputs as there won't be a server to tell it what to do.
 
All high end ATX power supplies from companies like Cosair, Seasonic, Thermaltake, etc, have active power factor correction and run at very nearly unity power factor.
 
Aye, the high end ATX units do have APFC, but tend to be 4 or 5 * the price of an equivalent server unit; also the server psu's output at a nominal 12v which is more suited to my plan whereas the ATX are designed to output only a portion at 12v.

actually, with some more searching I may have answered my own question - apparently with high power PSU's there's more onus on PFC, as a 500+w psu without APFC will draw quite high peak amps at full load - hence most server PSU's, particularly the higher output ones, are APFC.

so I've taken the plunge and bought the pair I was looking at.

thanks for the replies folks :)
 
Every year or three the European safety agency rules change, reducing the power supply wattage level at which mandatory PFC kicks in. I don't recall what the current number is, but I know it's below 500 W. So anything new will have PFC, and universal AC input is an excellent indicator of active correction.

ak
 
Aye, the high end ATX units do have APFC, but tend to be 4 or 5 * the price of an equivalent server unit; also the server psu's output at a nominal 12v which is more suited to my plan whereas the ATX are designed to output only a portion at 12v.

actually, with some more searching I may have answered my own question - apparently with high power PSU's there's more onus on PFC, as a 500+w psu without APFC will draw quite high peak amps at full load - hence most server PSU's, particularly the higher output ones, are APFC.

so I've taken the plunge and bought the pair I was looking at.

thanks for the replies folks :)

Although the deed is done methinks you're a little out of touch!

Today's mid to high end 500W power supplies for example at around £40.00 will give a power factor approaching unity and close to their full output power on the 12V rail.
 
Urr - I may well be out of touch, although I'm not sure which bit of that you consider so :confused:; I grant you that the higher output ATX units will give most of their rated power at 12v (although perhaps I should have said that when doing a conversion to single rail output, the extra rails of an ATX are just extra bits to be removed), and the high end 500w+ units do indeed tend to be APFC - probably for the excellent reason given by AK. As for the prices: well £40 for a 500w atx vs £15 for two 750W server psu's:- they certainly seem a lot cheaper to me :).
 
mm.. I'm not sure that's the case - APFC should basically match input amps to input volts - so if you use MSW then the current will be approx MSW too - I don't think they mind what the waveform is (within reason). The APFC psu's I'm familiar with use a boost convertor to boost the input up to 400v ish, putting a fair amount of energy into the 400v capacitor. from that point on the PSU is basically the same as a non-apfc psu; so, as long as it's a reasonable quality PSU i.e. with enough capacitor to hold up the output over the zero input volts part of the waveform, it should be fine - I think.
 
PSU is power supply unit
ATX err.. not sure now but an ATX PSU is what is fitted in most desktop/tower PC's

APFC is active power factor correction (as opposed to passive power factor correction): refers to power factor in A.C. loads: power factor 1 is where current and voltage track together - as the would in a simple resistive load - but 'reactive' loads, such as motors, transformers will have a phase shift between current and voltage which gives a PF <1.

MSW is modified sine wave - a waveform common in cheaper inverters/UPSs
 
I scrapped a dell server power supply, it did have pfc correction, its basically a boost converter on the front end of the supply that controlsthe voltage of the dc bus.
Better quality desktop pc (ATX) supplies can have them too.
 
What does ATX mean?

What does PSU mean?

What does APFC mean?

What does MSW mean?

You complained about acronyms before.

Google anyone of them followed by " acronym". You will get a list of the possible ones. Is not that difficult.
 
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