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power of a cold cathode bulb

Discussion in 'Lighting' started by artis sideley, Jun 28, 2007.

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  1. Hi all,

    What is the efficency of a cold cathod tubular bulb ? Is a 8W CCFL worth
    the light output of a 80W plain old incandescent bulb ?
     
  2. JohnR66

    JohnR66 Guest

    Not nearly enough information to answer your question.
    If your CCFL is similar in efficiency as the typical CFL, expect them to be
    3 to 5 times more efficient than the typical incandescent lamp runing in the
    15 lumens/w range.
    John
     
  3. If this is indeed a CCFL (cold cathode fluorescent) rather than a
    usual hot cathode hot cathode CFL, expect efficiency a little to somewhat
    less than that of the usual hot cathode ones.

    Decent hot cathode CFLs around 8-9 watts achieve about 50
    lumens/watt and produce roughly as much light as most 40 watt
    incandescents.

    - Don Klipstein ()
     
  4. First of all, no fluorescent lamp I know of is 10 times as
    efficient as an ordinary 80 -watt incandescent lamp would be
    if there were such a lamp. (I am using 75-watt and 100-watt
    incandescent lamps as my benchmark.) Very good fluorescent
    lamps are about 6 times as efficient as 75-watt and 100-watt
    120-volt incandescent lamps, and perhaps 7.5 times as
    efficient as 100-watt 230-volt incandescent lamps,

    Second, cold cathode fluorescent lamps are significantly
    less efficient than thermionic (hot) cathode fluorescent
    lamps UNLESS they have a high length-to-diameter ratio. If
    that is the case, they will have about the same efficacy as
    a hot cathode fluorescent lamp. The reason for the low
    efficacy of CCFLs with low length-to-diameter ratios is the
    very high voltage drop between the discharge and the cold
    electrode, compared to the much lower voltage drop between
    the discharge and a thermionic cathode. This high voltage
    drop can only be offset with a very high positive column
    voltage. High positive column voltage drops are present in
    lamps that have high length-to-diameter ratios.

    --
    Vic Roberts
    http://www.RobertsResearchInc.com
    To reply via e-mail:
    replace xxx with vdr in the Reply to: address
    or use e-mail address listed at the Web site.

    This information is provided for educational purposes only.
    It may not be used in any publication or posted on any Web
    site without written permission.
     
  5. BobT

    BobT Guest

    These numbers raise a question. Are plain old mass-market spiral
    CFL's pretty far below your "very good" lamps noted above?

    Looking at what I have in the basement, standard brand (Chinese GE)
    CFL's rated 6 watts are marketed as 40 watt equivalent; 13W as 60's,
    20W as 75's, 26W as 100's, and both 42W and 45W as 150's. All these
    numbers are in the vicinity of 4 times as efficient. Are CFL's
    inherently less efficient than your benchmark "good" lamps?
     
  6. Don Klipstein a écrit :
    Thanks,

    I knew the effective efficacy of Hot cathode CFL but I have no
    experience of CCFL as domestic lighting. So far, the only CCFL I know
    are used in LCD displays and as coloured advertising displays, those are
    rather efficiency poor.

    The commercial is deceptive then.
     
  7. Yes. I was referring to 4-foot linear T8 lamps. Spiral
    lamps have lower efficacy both because their diameter is
    smaller than optimum for the power levels they operate at,
    and the spiral design traps light.
    Yes, for the reasons mentioned above.

    --
    Vic Roberts
    http://www.RobertsResearchInc.com
    To reply via e-mail:
    replace xxx with vdr in the Reply to: address
    or use e-mail address listed at the Web site.

    This information is provided for educational purposes only.
    It may not be used in any publication or posted on any Web
    site without written permission.
     
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