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From: Terry King
Subject: Re: TRIAC "wears out" on dimmer circuit
Date: Mon, 28 Oct 2002 21:40:59 -0500
Organization: Waits River Valley School
X-Newsreader: MicroPlanet Gravity v2.30.1784
> > > ** 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 .
Regards, Terry King ...In The Woods In Vermont
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