Active/Passive PFC vs. Non-PFC

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Thread: Active/Passive PFC vs. Non-PFC

  1. #1
    Reef Shark CookIEZ's Avatar
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    May 2004
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    Active/Passive PFC vs. Non-PFC

    I think that Active PFC would be the way to go. Was reading an article and it said that it eliminates harmonics as well as increases efficiency. Not sure how important this is in PC's or if it even makes a difference.

    Thoughts?
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  2. #2
    Catfish
    Join Date
    Aug 2004
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    Just a little Power Factor primer here from my days as an electrician in the Navy's nuclear power program.

    "Power Factor" has to do with the relationship of voltage and current. Due to inductance or capacitance in a circuit, there is a phase shift (in an inductive circuit, the current lags behind the voltage... in a capacitive circuit, the current leads the voltage) which results in circulating currents and some energy loss.

    The wasted power is called "reactive power." The theoretical power required for the circuit is the "real power." The power actually required to power a circuit is a combination of the two, and is called "apparent power." With a unity power factor (completely corrected) there is no reactive power, so real power and apparent power are the same. (Note: the electric company charges you for "apparent power")

    Bad things caused by this are inefficiency (you waste power because you are drawing power that basically doesn't do anything) and heat generation.

    I'm not sure about the harmonics part... obviously these circulating currents generate some "noise" in the circuit, but I don't think that part is a major concern. Of course, the cleaner your power the better - but I don't know if the improvement in the quality has an practical benefit.

    So the end result is... a power supply with PF correction will cost less to operate and will generate less heat.

    It will also give a cleaner signal, but I don't know if the difference is anything that would provide a benefit.

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