Re: power of a cold cathode bulb

On Thu, 28 Jun 2007 22:30:54 +0200, artis sideley
<artis-point-sideley@xxxxxxxxxxxxxx> wrote:

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 ?

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
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