Re: How do Philips X-treme power bulbs work?


"Don Klipstein" <don@xxxxxxxxxxxxxx> wrote in message
news:slrngeduee.aof.don@xxxxxxxxxxxxxxxxx
In <K2hFk.58914$Mh5.726@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>, TKM wrote:

"Don Klipstein" <don@xxxxxxxxxxxxxx> wrote in message
news:slrngeajcl.8dr.don@xxxxxxxxxxxxxxxxx
In article <6kk2m8F894ltU1@xxxxxxxxxxxxxxxxxx>, JB wrote in part:
<I snip to edit for space>
The metallurgy of these filaments is rather special as you would expect.
Actually though, tungsten filaments are more fragile when cold.

My experience tells me otherwise.

If I drop or bang an incandescent lamp that has long wires leading
to the filament, and do so while the filament is cold, I find it hard
(but
not impossible) to break or stretch the filament without also bending
the
wires leading to the filament.

When the filament is hot, I find it easy to stretch the filament out of
shape by so much as rough tapping of the lamp. Sometimes, worse still,
I
end up stretching only part of the filament - and that can make the
unstretched portion hotter than before. (The stretched portion is
cooler,
has less resistance, and more current flows through the entire
filament.)
Also, uneven filament temperature leads to uneven evaporation, and the
hotter parts of the filament become acceleratingly severe hot spots once
significant evaporation has occurred.

And if there is a lot of vibration just short of stretching the
filament, that will cause significant metal fatigue. I think that is
more
of a problem with a hot filament than with a cold one.

Incandescent trouble lights seem to me to easily have their filaments
stretched out of shape or outright broken from impacts while they are on
and not while they are off.

I don't think its so much the stretching of the filament as it is the
shorting of the coils in the coiled-coil filament. When line voltage
lamps,
particularly halogen, are moved or subjected to vibration, the coils bang
together and short circuit. That makes the voltage goes up on the
remaining
length of filament which then fails or burns hotter shortening life. The
50PAR20 is particularly sensitive and requires very gentle handling when
aiming the fixture.

Oh you remind me! I have a bit of experience with filaments partially
short in 120V lamps from shock/vibration!

I have seen that happen with filaments of C-7A and CC-2V style.

In the case of C-7A: Nightlight lamps and similar 120V holiday lamps,
when tapped in rough manner by a finger (plucked), especialy if
impacted such several times, can have a small region of filament get
tangled with a small region of a nearby portion of filament.
This appears to me to occur more easily if impacts (with the filament
hot) stretch the filament so that the filament has slack and sections of
it easily flopping around.
I used to do that a bit as a "party trick" - to make such lamps glow
brighter and whiter. That was maybe 30 years ago, and back then I was not
thinking that much that I reduced the lamp's life expectancy to maybe a
few days.
On a bit of a sidetrack, those lamps had bulb shape/size designation of
C7 and a common nominal wattage for those was 7 watts. Since then there
have been 4 and nowadays some 5 watt ones with C7 bulb and C-7A filament.
There is a larger usually-colored "older type holiday lamp" with bulb
shape/size designation of C9. Its wattage is typically 7 or 10 watts and
the filament is usually C-7A. The base of that one is often "intermediate
screw", which often makes the part number get an "N" towards the end.

In the case of CC-2V: I forget whether that was "normal CC-2V"
(pointing away from base) or inverted (and I wonder what the designation
for that is anyway). However, those were V-shaped coiled-coil filaments
with one support at the "corner" between the ends.
The lamp was a chandalier style one, of wattage probably 40 or 60 watts
but I can't rule out 25, and the bulb was of one of those F or similar
flame shapes.
Where I saw such lamps having filaments partially shorting, the
filaments had a short somewhat close to "the vertex of the V", apparently
due to vibration/shock jostling the filaments and possibly stretching the
filaments also to make the filaments entangle into such "partial shorts"
more easily.
Where I saw such CC-2V filaments shorting was in a fraternity house at
the University of Pennsylvania (when I was making a delivery to that
house), back in a day when fraternities at U-of-P had an easier time
having parties with beer kegs in their houses. The affected/afflected
filaments appeared to me especially "stretched/floppy", except the ones
that partially shorted but had yet to fail appeared to me "not-too-floppy"
(and also appeared to me having fair to poor chance of surviving into the
next party).
I did appear to me that the filaments were stretched into a "floppier
state" and I happen to think that the filaments were stretched into an
"easier-to-partially-short state" while the filaments were hot, as in
"in-use to produce light".

As for shorting effects specific to coiled-coil where "greater turns"
short to adjacent ones - that one I have yet to see, but I don't yet have
doubt that this one can occur if the "greater turns" are wider and/or
the "compacted overall length" is shorter than usually used in coiled-coil
C-6/C-8 filaments in 120V A19 lamps.

- Don Klipstein (don@xxxxxxxxx)

Tungsten filaments, when new, are relatively stiff and I'm not convinced
that they stretch although they certainly flop around and they do move
inside the filament support loops . Try this (it requires sacrificing a new
lamp, however): Take a candelabra-based lamp apart. They typically have,
as you say, CC-2V filaments although some have C-7A designs (more filament
supports). Remove the filament and pull on the ends. It takes quite a bit
of force to stretch that filament, so even after some burning hours as the
filament becomes brittle, it doesn't seem likely that it stretches. But, if
so, the "CC" filament would stretch more than the "C" types.

A story was told to me some years ago by the product service people of a
large lamp manufacturer. It seems that they had received a complaint about
short lamp life of candelabra-based lamps in a dining room chandelier. The
complaint was puzzling since dozens of lamps had failed over a few weeks
time and there were no other complaints pending for that particular lamp
type. The person complaining happened to be fairly close to the offices of
the company so a local lamp engineer was dispatched to see what the problem
might be. An evening visit was arranged and the engineer confirmed that
lamps were indeed failing, but that the lamps were current production and
the voltage at the lamp sockets was below the lamp rating. There was no
dimmer on the circuit. Puzzled, the lamp engineer left a voltage recording
device on the circuit and arranged another visit for a week later.

That visit turned up more failed lamps, a record of less-then-rated voltage
on the lines and an increasingly-grumpy customer. As the frustrated
engineer was about to leave, however, there was a loud thump from upstairs
that shook the whole room including the chandelier which actually moved
several inches. Problem solved. The noise was due to the teenage son
jumping from the top level of a bunk bed onto the bedroom floor which he
did, with some pleasure, several times a day. A gym pad on the bedroom
floor damped the worst of the vibrations and reduced lamp failures; but the
problem wasn't solved until the bunk bed was moved to another bedroom.

The episode generated research on filament failures and a technical paper
written a few years later concluded that vibration and shock failures in
small decorative lamps accounted for a fair percentage (30-50%, as I recall)
of failures before rated life.

Terry McGowan




.

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