On Thu, 28 Aug 2003 12:44:54 -0700, the renowned "William Sommerwerck"
wrote:

Thanks for the confirmation of 12th power.

The 12th power approximation does originate at GE Lighting, AFAIK, but
is only valid for voltages rather close to the rated operating
voltage, and for typical high voltage incandescent lamps. Long-life
and halogen bulbs WON'T behave the same.

http://www.eaoswitch.com/about/lamps.htm

Here's a rule of thumb for low-voltage halogens:

http://www.ndlight.com.au/low_voltage_lighting.htm

They claim a 5% voltage increase will reduce life by 50%, which is
more like the 13.5th power.

The one time I checked the 12th power approximation against actual
testing of low wattage high voltage (mains) lamps it was off by more
than an order of magnitude, so take the whole thing with a grain of
salt, IMHO, unless your lamp type matches the type used for testing.
I'm sure a real lamp specialist could go on for hours about this sort
of thing.

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
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