From: dxmm@albury.nospam.net.au
On 22/04/14 04:26, Uncle Peter wrote:
> On Mon, 21 Apr 2014 12:22:39 +0100, Daniel
> wrote:
>
>> On 21/04/14 05:03, Uncle Peter wrote:
>>> On Sun, 20 Apr 2014 12:17:45 +0100, Daniel
>>> wrote:
>>>
>>>> On 18/04/14 22:45, Uncle Peter wrote:
>>>>> On Fri, 18 Apr 2014 12:48:36 +0100, Daniel
>>>>> wrote:
>>>>>
>>>>>> On 17/04/14 23:46, Uncle Peter wrote:
>
>>>
>
>>>>>> Wouldn't cause a very big blip in the grander scheme of things.
>>>>>>
>>>>>> And what SMPS clips off the peaks?? Usually they vary the switch on
>>>>>> point in the A.C. waveform.
>>>>>
>>>>> You can get power supplies with "active PFC" which is presumably what
>>>>> you just described. However the cheap ones have "passive PFC" or no
>>>>> PFC, so presumably they just top up the bulk capacitors at the peak of
>>>>> each waveform. A basic transformer and rectifier will do the same.
>>>>>
>>>> What's "PFC" when it's at home?? Power Factor Correction maybe!!
>>>
>>> I know that.
>>
>> But *I* didn't, which is why I asked "What's "PFC" when it's at home??"
>
> When you immediately answered yourself, with two shriek marks, I assumed
> you were telling me.
What part of the world are you from?? In some parts of the world, the
first thing people might think when they hear "PFC" would be "Private
First Class"!!
>>>> To the mains supply, most things look like Inductors, which means the
>>>> voltage waveform and the current waveforms are not in phase. Power
>>>> Factor Correction simple means that capacitors are switched in to
>>>> counter-act the Inductance, so the Voltage and Current are more nearly
>>>> in phase.
>>>
>>> And at different power level draws from the output of the power supply,
>>> presumably a different capacitance is ended to correct it. Active PFC
>>> probably changes it accordingly. Or adjusts the other type of power
>>> factor which you haven't mentioned - wave clipping.
>>
>> I'm guessing just one, very big, capacitor which can handle the
>> filtering task for all loads up to the Power Supply's rating.
>
> But surely if it's not adjusted, then it's overcompensating when the
> supply is not fully loaded.
No, in a Switched Mode Power Supply, as the load varies, it is *Switched
On* for more of less of the Alternating Cycle. If the supply's output
(Current/Voltage) is falling below the required (Current/Voltage), the
Switching element/transistor is switched on for more of the input cycle,
not the input voltage!!
>>>> Active PFC might be changing how a transistor "appears" (more
>>>> capacitive
>>>> or less capacitive) to fix the phase angle.
>>>>
>>>> And, as I typed earlier, your little power supply would have very
>>>> little
>>>> effect on the phase angle of your homes mains supply!!
>>>
>>> How about ten 850W power supplies?
>>
>> 10 x 850 watt power supplies, total 8.5kW, from a 240V supply takes
>> about 35Amps, .... and lets double that to allow for transformer and
>> other circuitry loses = 70Amps!! Whoopee!! from your regional Power
>> Company, which probably supplies THOUSANDS of Amps!!
>
> You said "very little effect on the phase angle of your homes mains
> supply!!" It's probably 90% of my home's supply.
At some particular moment, you might be correct that the power supply is
having this great effect, but over a day/week I doubt it would be
anything like 90%!
>>>> Now, when your refrigerator's (inductive) motor switches on, now that
>>>> might have a noticeably affect, but, in the greater scheme of your
>>>> regional Power companies operations, zero effect!!
>>>
>>> Or my industrial grade meat freezer.
>>
>> What's that, another 10kW!! WOW!! or rather Whoopee!! And remember the
>> freezer motor is not working 24/7 (or at least it shouldn't be), so its
>> real power consumption would be much lower, maybe 1kW at most!!
>
> Yes, I was just pointing out I have a ridiculous freezer.
>
Wacko!!
Daniel
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