Re: Insteon Observations

[nobody@xxxxxxxxxxxx (Dave Houston)]

G. Morgan <alarmpro@xxxxxxxxxxx> wrote:

>On Fri, 15 Dec 2006 18:04:57 -0500, Marc_F_Hult
><MFHult@xxxxxxxxxxxxxxxxxxxxx> wrote:

>>When a tungsten filament fails, a "tungsten arc" can occur through vaporized
>>tungsten connecting the ends of the foreshortened filament. There is a
>>positive feedback in this effect, so as more tungsten is consumed to support
>>the arc, the current path through the remaining filament becomes shorter, and
>>the current increases causes more vaporization. This can result in the bright
>>flash that is sometimes seen when a filaments fails.
>>
>>This is a well-known phenomenon. Some lamps have fuses built into the base to
>>provide some measure of protection. One of the functions of the RC snubber
>>circuit across a TRIAC is to protect the TRIAC gates from inductive spike
>>during filament failure that can damage the TRIAC. This is also a problem with
>>IGBT and MOSFETs used in reverse phase dimmers.
>
>Marc,
>
>So the net effect is indeed a current surge while the light bulb
>filament is breaking apart?
>
>(x-posted to sci.engr.lighting,alt.engineering.electrical,sci.physics)

The "tungsten arc" is indeed well-known and most household light bulbs have
the built-in fuse to prevent it from blowing mains fuses or tripping circuit
breakers (or even destroying triacs). How many people have had a circuit
breaker pop when a bulb blows?

I've recently had a spate of bulb failures that I attribute to ultra-cheap
imported bulbs. They blew "not with a bang but a whimper" (actually, more
like a "poof") and they did not harm the lamp modules (LM14A & LampLinc V2).
Most (all but one) of my lamp modules are plugged into power strips with 15A
breakers since I cannot get to the basement to replace fuses - none of the
breakers have tripped.

Given that the folks behind Insteon have been designing triac dimmers for
several years, why would they have not taken this into account?

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