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Re: Power Factor - was Re: Sylvania Quicktronic 32 Electric Ballasts
Suzy Jackson wrote, in part:
"The power factor is not related (at least in a direct sense) to the
efficiency of a device.
Power factor relates to the proportion of real to apparent power that
the device consumes. Most of the loads in a household or industrial
setting (including magnetic ballasts) are inductive, and thus have a
lagging power
factor."
Thanks for the excellent correction. The use of the term "Power
Factor" that you mention is precisely that which is used in in the
industry for electric motors, and probably what should be used for
florescent ballasts. In fact, it is often stated right on larger AC
motors (True DC or Universal motors always have a Power Factor of
Precisely 1). But most people don't use the term that way when talking
about ballasts, including the GE web site. But that doesn't mean they
aren't wrong or that I should perpetuate the confusion. So in my prior
comments I should have simply used the term (energy "efficiency" of
"efficacy") even though, as you point about, higher Power Factors,
other things being equal, mean higher efficiency.
And, of course, adding capacitors to compensate for inductive drags or
losses in power factor does not allow one to actually achieve unity in
practice. That would require perfect symmetry which is rarely
attempted in fluorescent devices even though the range of frequencies
one has to deal with in a ballasts is small. A related problem plagues
the design of audio circuitry, where the phase shifts in the wave form
constitute distortion. In those cases, the distortion itself (the
altering of the wave form) is usually considered the problem, not the
loss of energy that goes with it. Even-ordered correction circuits can
bring the things back in phase, but there is always a loss of energy
along the way as well as timing differences that can't be avoided --
Those damn laws of physics interfering again. ;-)
I'm not sure that I agree that efficiency is important in a crowded
hood -- at least, not as a general statement. My only point of
disagreement here, if any, is that the amount of wasted energy between
an efficient and an inefficient ballast that one is likely to come
across is so small compared to what the lights are wasting. Rather
than spend an extra few hundred dollars for an increase form 90% to 93%
efficiency, one might be better off (for practical or financial
reasons) using more efficient bulbs or buying a fan to drive off the
heat. Other things being equal -- and they rarely are--, efficient
ballasts are cooler and allow relatively more current to the bulb where
it might or might not produce more light instead of just more bulb
heat.
Scott H.
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