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Subject: Re: Halogen bulb drive
Date: Wed, 25 Sep 2002 04:59:14 +0100
References: <4LPj9.firstname.lastname@example.org> <email@example.com>
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"Phil Allison" wrote:
>> The most significant factor in life (ignoring mechanical vibration and
>> shock) is applied voltage. Life being inversely proportional to 12th power
>> of the ratio of specified and applied voltage.
> ** That is exactly what I have found - silly stories, not facts.
> The extended life of halogen bulbs mainly derives from the use of
>thick filaments in the low voltage ones and the same is also true in high
>powered 120 volt ones like Par 64s et alia.
> 240 volt low power halogens are both very fragile and short lived
>unless the colour temp is way down - your 12th power comes into play here.
Yep there is quite a lot to halogen lamps. The brighter you want the
shorter they live, some of the small bright ones were rated for only 3-4
It is also possible to reduce life with under voltage operation, apart from
discolouring the envelope. There are choices in the mix and concentration
of Halogens used. One manufacturer told me of problems a customer had
running projector type lamps significantly undervoltage for extended life
and the aggressive mix used in them was damaging the filaments running at
lower than normal temperature.
What I was actually trying to find out was how bad (or good) an idea it was
for a brightness regulator to stabilise filament resistance.
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