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From: "Phil Allison"
Subject: Re: TRIAC "wears out" on dimmer circuit
X-Newsreader: Microsoft Outlook Express 5.50.4522.1200
Date: Tue, 29 Oct 2002 15:16:56 +1100
NNTP-Posting-Date: Tue, 29 Oct 2002 15:07:54 EST
Organization: Telstra BigPond Internet Services (http://www.bigpond.com)
"Terry King" wrote in message
> > > > ** An arc across the remaining ends
> will never be anything like 60 amps
> I have also read about this and seen the effect. It is most pronounced
> when short tungsten-halogen lamps fail open while powered on. The
> physically open filament creates a METAL arc for a short period of time,
> and the dynamic lamp resistance is far LOWER than the connected filament
> was. The current does not just flow from the broken ends of the
> filament; the metal arc flows all around the attaching metal rods
> that go thru the seals, as well. Good theatrical dimmers have special
> fuses (Silver conductor in a sand-filled ceramic tube) that "blows"
> fast under high currents to protect the TRIACS / SCR's .
** Yep, I have heard of this too. But AFAIK it is restricted to high
powered lamps and not typical domestic ones or even things like Par 38s.
. ... ........... Phil
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