Re: Insteon Observations
G. Morgan
<MFH...@nothydrologistnot.com> wrote:
>On Fri, 15 Dec 2006 22:27:03 GMT, nob...@whocares.com (Dave Houston) wrote in
>message <45831e9f...@nntp.fuse.net>:
>
>>"Dennis Brothers" <brot...@abbreviatemysurname.com> wrote:
>>>
>>>Hard to imagine how a defective LampLinc could damage an ordinary 100W
>>>incandescent bulb. On the other hand, it's easy to see how a current surge
>>>as the bulb dies (typically accompanied by a blue flash) could damage a
>>>triac.
>>>
>>
>>Why would there be a surge when the (resistive) circuit opens? The inrush
>>current when a cold incandescent is turned on is significantly higher than
>>after the filament heats up. If the filament is thin in a spot, the normal
>>inrush current causes it to break.
>
>Dave,
>
>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)
Thanks,
--
-Graham
(delete the double e's to email)
G. Morgan
>Dave Houston wrote:
>> G. Morgan <alar...@geemail.com> wrote:
>>
>>> Anyway, I have never experienced what you describe (a circuit breaker
>>> trip) on failure of a bulb. My common sense tells me the arc (air gap
>>> resistor) would be a great, sudden, resistance that would indeed draw
>>> a large current spike. Part of me thinks the opposite is true - for
>>> which I have no basis!
>>>
>>> I was not aware that common bulbs had a fuse either, I thought the
>>> filament IS the fuse.
>>>
>>> My interest in this has nothing to do with Insteon devices, it has
>>> more to do with what I can do to protect the circuit for devices I
>>> install, if the theory is true. It may explain some anomalies I've
>>> experienced with security devices.
>>
>> The tungsten-arc is for real. The built-in fuse is also. If you hear a "pop"
>> and see a bright flash, you're buying cheap bulbs. If you hear a "poof" and
>> notice a bit of a flicker before darkness descends, your bulbs are fused
>> (even if cheap).
>>
>> The inrush current for an incandescent is about 10 times the current once
>> the filament has warmed to its normal temperature. For a 100W bulb this
>> means an inrush at turn-on of +8A. The "fuse", if any, built in to the wire
>> leading from base to the filament should withstand the inrush but blow
>> before a 15A breaker is tripped by a tungsten-arc.
>Come on... This is all like discussing how many angels can dance on the
>head of a pin...
>
>In reality, don't most folks buy light bulbs at Home Depot, Lowes,
>Target, Walmart, (or at their local food store if they ran short)!
>
>I doubt that 99.9999% of the folks would buy "fused bulbs" vs "unfused
>bulbs" but will buy what's on sale.. Do you all not have a life?
The fundamental question for me is whether or not light bulbs can
cause equipment damage. And no, I have no life.
Victor Roberts
Yes.
--
Vic Roberts
http://www.RobertsResearchInc.com
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Victor Roberts
If the branch circuit has appreciable inductance, then when
the current first increases and then abruptly goes to zero
when the internal fuse blows, a small voltage spike could be
generated. This could damage other equipment on the same
branch circuit, but I have never seen or heard of such
damage.
TKM
"G. Morgan" <alar...@geemail.com> wrote in message
news:cnt6o2p66td2u9s7k...@4ax.com...
Yes, a failing incandescent lamp can cause a current surge if the filament
arcs as it falls apart. That's been well known for years. Incandescent
dimmer manufacturers usually handle the situation by inserting a small
impedance in the output circuit to protect the solid state parts which, of
course, act faster than the thermal fuse in the lamp.
General service inandescent lamps are gas filled and fused. That's because
when gas-filled lamps were developed in 1913, manufacturers learned quickly
that an arcing filament was bad for business as it caused lamps to shatter,
bases to melt and sparks to fly around.
Terry McGowan
Bud--
I knew that UK bulbs at 230V would arc and had fuses but until recently
I didn't think it was a problem in 120V bulbs. Where is the fuse hidden?
--
bud--
Victor Roberts
The lead wire from the center of the screw base is a fuse
wire.
TKM
"Bud--" <remove....@isp.com> wrote in message
news:cf341$4585a877$4213ea40$46...@DIALUPUSA.NET...
The fuse is in one of the leads in the "stem" or glass support structure for
the filament. If you take a lamp apart, you will see that there are
different kinds of wire going from the base or cap up to the filament. The
filament, of course, is tungsten. The support wires are Molybdenum, but
they are welded to a wire of nickel-iron alloy covered with copper called
Dumet which has the same coefficient of expansion as the glass which
surrounds them. In one of the leads toward the cap, there is a fuse wire as
well. It may be inside a tube surrounded with glass beads called ballotini
which helps to quench any arc as the fuse opens. All lamps sold in the
European Union must have a fuse which complies with IEC 432-1, a lamp safety
standard. I don't know if there is a similar standard for the fuses used in
North American lamps.
Terry McGowan
Marc_F_Hult
in message <4582f3bf...@nntp.fuse.net>:
>"Dennis Brothers" <brot...@abbreviatemysurname.com> wrote:
>>Even more alarming is that
>>I've had three or four LampLincs die when bulbs they were controlling
>>burned out.
>
>Could it be the Lamplincs went bad and took the bulbs out? I think that's
>more likely.
What are the physics of the mechanism(s) that would cause a INSTEON
Lamplinc dimmer (TRIAC output device typical of residential US dimmers) to
'take out' lamps?
And why, as Dave thinks, is this "more likely" than the well-known
phenomenon of a current surge owing to tungsten arc when the filament fails
causing the TRIAC in the dimmer to fail?
... Marc
Marc_F_Hult
www.ECOntrol.org
Robert L Bass
>>> three or four LampLincs die when
>>> bulbs they were controlling burned
>>> out.
>>
>> Could it be the Lamplincs went bad
>> and took the bulbs out? I think that's
>> more likely.
Nonsense!
> What are the physics of the mechanism(s)
> that would cause a INSTEON Lamplinc
> dimmer (TRIAC output device typical of
> residential US dimmers) to 'take out'
> lamps?
>
> And why, as Dave thinks, is this "more likely" than the well-known
> phenomenon of a current surge owing to tungsten arc when the filament fails
> causing the TRIAC in the dimmer to fail?
Be happy it wasn't a Z-Wave dimmer. Dave would have explained (with copious documentation) how RF vibrations blew the bulb. :^)
--
Regards,
Robert L Bass
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