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From: "Phil Allison"
References: <4LPj9.firstname.lastname@example.org> <email@example.com>
Subject: Re: Halogen bulb drive
X-Newsreader: Microsoft Outlook Express 5.50.4522.1200
Date: Wed, 25 Sep 2002 12:27:56 +1000
NNTP-Posting-Date: Wed, 25 Sep 2002 12:16:50 EST
Organization: Telstra BigPond Internet Services (http://www.bigpond.com)
"nospam" wrote in message
> "Phil Allison" wrote:
> >> DC voltage across the lamp also causes thinning at one end.
> > ** Have you any published figures on this? Is it a factor at 12
> >24 volts?
> If this were a significant factor then all dc driven filaments would fail
> at one end - news to me if they do.
> I did quite a lot of research on small halogen lamps some time ago. I came
> across a mention of this ac/dc phenomena or rumour - I didn't find
> I believed.
> Also came across soft starting extending lamp life stories without any
> serious grounding. Yes they often fail at power on but only when they are
> about to expire anyway.
> 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.
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