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A few measurements...

Discussion in 'Home Power and Microgeneration' started by Ecnerwal, Aug 25, 2006.

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  1. Ecnerwal

    Ecnerwal Guest

    So, I finally pried my wallet open and bought a P3, leading to the usual
    round of measurement-itis, though maximal minimization is not truly
    effective for my off-grid plans (need to run motors in my shop, going to
    need power to do that - though I still don't want to waste much).

    The good: for all of being a 850+watt powersucker when it runs, the
    morning coffee is only costing 90-100 watt-hours. While I have brewed
    coffee on the stove, the less I have to fiddle with things before I get
    my coffee in, the better.

    The bad, or at least needs correction capacitors (I assume, not having
    dragged out the oscilloscope, that it needs capacitance added):

    Picked up a 70 watt high-pressure sodium fixture for potential use as an
    outside light over the shop door. During startup it draws a mere 35
    watts, but 225 VA. once warmed up, it draws 75 watts, but is still
    cooking along at 186 VA - and these things get used a lot for their
    efficiency...sheesh. 0.15 to 0.40 PF, and that sickly orange light to

    The "not even modern" dual tube "40 watt T12 tubes running at 35 watts"
    florescent fixture draws 67 watts and hits a PF of better than 0.75 in a
    few minutes of operation. I'll get around to checking the supposedly
    better modern T8 fixtures one of these days.
  2. Guest

    Will a cap help, or is it distortion vs a phase lag? With PF = 75/186 = 0.4,
    you might try reactance Xc = 120^2x0.4/(75sqrt(1-0.4^2)) = 84 ohms with
    C = 1/(377x84) = 32 microfarads.

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