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Active PFC?

Discussion in 'Electronic Equipment' started by Computers911, Sep 23, 2003.

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  1. Computers911

    Computers911 Guest

    Hello:

    I'm hoping to save energy by replacing my current PS with one which has
    Active PFC. But before I do, I'd like to figure out if it's worth while.
    How do I determine how much energy is currently being used by my computer?
    The company how's product I'm interested in purchasing is called
    Thermaltake...they were on help in explaining to me the energy savings. The
    product info. is @ the following link:

    http://www.thermaltake.com/products/purepower/w0006r.htm

    Thanks in advance....
     
  2. Chris Oates

    Chris Oates Guest

    Non-PFC offers around 0.5~0.6 PF (Power Frequency), 40%~50% power lost.

    they talk rubbish which doesn't inspire
    much confidence
     
  3. ctsbillc

    ctsbillc Guest

    Power factor isn't about efficiency, it is about the way the power supply
    draws current, which without PFC distorts the power waveform and presents a
    bad load to the generator.

    You will not see any dollar savings with a PFC supply, it will use a bit
    more power, but it will present a cleaner load to the power grid.

    Bill C
     
  4. Chris Oates

    Chris Oates Guest

    In the UK if you had enough equipment to significantly
    lower your power factor you can (on the correct tarrif)
    install power factor correction & save money.
    (one PC won't do it)
     
  5. Computers911

    Computers911 Guest

    Ok, so if there is no dollar savings in an Active PFC power supply, why is
    the manufacturer of the power supply talking about lost power? I don't
    understand the terminology.

    Say for example that I have two power supplies. Each is rated at 360Watts.
    One is non-PFC and the second has Active PFC. According to what you said,
    they both still use the same amount of power? So the 40-50% power loss
    would mean that I can hook up fewer devices to a non-PFC power supply?
    Which would mean I could use a lower wattage Active PFC power supply to
    support the same number of devices that a non-PFC power supply would
    support? If that's right, then I could use a 216Watt Active PFC power
    supply to do the same job as a 360Watt non-PFC power supply ( assuming a 40%
    power loss on the power supply that's non-PFC )?

    I hope the above is correct .... otherwise I'll just give up.
     
  6. The one with poor power factor would draw more current, so you
    couldn't put as many on the same circuit, or, if large, you might need
    a circuit with greater capacity. The extra current drawn by the
    non-PFC supply doesn't do any work (it is like reactive current), so
    it doesn't add to the output power. The output power would be the
    same for both, but the non-PFC one would _appear_ to draw (say) 700
    watts if you just looked at voltage and current.

    PFC does increase efficiency of the electrical wiring a bit, since
    there is lower current, hence lower wiring losses.

    Regards,
    Allen
     
  7. Fred Abse

    Fred Abse Guest

    I think you mean "Power Factor"
    Not true, if we're talking power factor, the "lost" power is returned to the
    supply each half cycle. The consumer won't be paying for it, if his meter
    is properly designed.

    Active power factor correction only makes much sense to supply companies,
    who want their voltages and currents as nearly in phase as possible.
    Unless the load is quite large, the extra losses in wiring won't be more
    than a few cents a month.

    As do most companies playing on the susceptibilities of the average
    non-technical punter.
     
  8. I suspect that whoever wrote that simply doesn't understand what they
    are talking about. A power supply with poor power factor doesn't "lose"
    power, but it does draw almost all its power near the peak of the AC
    waveform. A PFC corrected supply draws current throughout the AC
    waveform. Ideally, current would be proportional to voltage.
    The 360 watt spec is the maximum output power. With 360 W out, the
    input power is somewhat higher - but probably about the same for both
    designs. If you reduce the load to 180 W, the input power will also
    drop in half (or nearly so). The supply doesn't "use" much power
    internally.
    No, both have the same output rating. And the "40-50% power loss" is
    nonsense.

    Dave
     
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