Re: Quietish budget PSU


"John Jordan" <junk@xxxxxxxxxxxx> wrote in message
news:3mkdeiF16rpbpU1@xxxxxxxxxxxxxxxxx
> Synapse Syndrome wrote:
>> "John Jordan" <junk@xxxxxxxxxxxx> wrote in message
>> news:3mficfF16bu2jU1@xxxxxxxxxxxxxxxxx
>>
>>
>>>However, quietness and PFC are not necessarily related to efficiency.
>>>
>>
>> How can quietness not be related to efficiency? If the power supply is
>> efficient, it will produce less heat. If it is less hot, there is less
>> need for fans, so they can spin slower, or replaced altogether with
>> heatsinks.
>
> That's correct. "Not directly correlated" would have been a better phrase.
> You can have a very quiet PSU that isn't very efficient, and you can have
> a very loud PSU that's also very efficient. However, it's easier to make
> an efficient PSU quiet.
>
> Note that efficiency for a particular PSU is not constant. A PSU will
> generally be less efficient at light loads.
>
>> And the whole point of PFC is efficiency, with active PFC being more
>> efficient and costly than passive PFC...
>
> Efficiency of mains wiring and beyond, not the power consumption of the
> PSU itself. Because PCs are usually a tiny fraction of maximum home
> consumption, it's unlikely to make any measurable difference anywhere
> because the cables are rated at 3KW+. Maybe if you had a few racks of PCs
> running SETI.
>
> One situation where it may make a difference is when you're running off a
> UPS. With a lower PF, you'd need a higher VA rating and your run-time may
> be less.
>
>
>> Hmmn. http://en.wikipedia.org/wiki/Power_Factor_Correction
>> "Power factor correction (PFC) is a widely used technique in electrical
>> engineering used to counteract the effects of load capacitance or
>> inductances that would otherwise lead to an undesirable power factor,
>> which wastes energy. It is designed to work on an AC power circuit so
>> that as little reactive power as possible is transferred between source
>> and load."
>
> Doesn't state where the power is wasted, so no contradiction.
>
>> http://www.endpcnoise.com/cgi-bin/e/pfc.html
>> "The preferable type of PFC is Active Power Factor Correction (Active
>> PFC) since it provides more efficient power frequency. Because Active PFC
>> uses a circuit to correct power factor, Active PFC is able to generate a
>> theoretical power factor of over 95%. Active Power Factor Correction also
>> markedly diminishes total harmonics, automatically corrects for AC input
>> voltage, and is capable of a full range of input voltage. Since Active
>> PFC is the more complex method of Power Factor Correction, it is more
>> expensive to produce an Active PFC power supply."
>
> Doesn't state the effect of diminishing total harmonics, so no
> contradiction.
>
>> http://www.ibiblio.org/obp/electricCircuits/AC/AC_11.html
>> "In a purely resistive circuit, all circuit power is dissipated by the
>> resistor(s). Voltage and current are in phase with each other.
>> In a purely reactive circuit, no circuit power is dissipated by the
>> load(s). Rather, power is alternately absorbed from and returned to the
>> AC source. Voltage and current are 90o out of phase with each other. "
>
> Direct agreement, but no discussion of consequence.
>
>> "....This lower total current will translate to less heat losses in the
>> circuit wiring, meaning greater system efficiency (less power wasted)."
>
> "circuit wiring". No mention of magnitudes, so no contradiction.
>
>> http://www.zalman.co.kr/eng/product/view.asp?idx=76&code=
>> "By implementing Active PFC, the power factor (PF) is improved from 75%
>> (Passive PFC) to 94% (at full load), while harmful harmonic frequencies
>> are reduced below regulatory requirements."
>
> Again, doesn't state the effects of reducing harmonics. No contradiction.
>
>> I think that these cites can be taken as more authorative than Dan's
>> Data, which is just full of one guy's personal views on thing.
>
> They don't contradict him though, and he does explain the reasoning in
> detail so you can decide for yourself. Personally I spent two hours
> testing PSUs with a wattmeter :-)
>
> I'm a little surprised that you didn't find a single quote that claimed a
> direct link between power factor and PSU efficiency. I'm sure there are
> plenty around.
>
>
> A review I found, showing no link between PFC and efficiency, although
> unfortunately no power factor measurements:
>
> http://www.techreport.com/reviews/2004q4/psus/index.x?pg=1
> http://www.techreport.com/reviews/2004q4/psus/index.x?pg=15
>


I really recommend that you invest in a high quality Active PFC power supply
unit, maybe a Zalman or Tagan. They are very quiet and hardly get warm at
all. You will never look back.

ss.


.

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