Functions of voltage for tungsten lamps?

[ITSME.ULTIMATE]

Does anyone know the functions of voltage for the tungsten halogen lamp?

The 1984 edition IESNA Lighting Handbook gives a graph and functions for
vacuum and gas filled type lamps.

I think the life function is considerably different because of the
halogen cycle.

Thanks

 

[Don Klipstein]

Does anyone know the functions of voltage for the tungsten halogen lamp?

The 1984 edition IESNA Lighting Handbook gives a graph and functions for
vacuum and gas filled type lamps.

I think the life function is considerably different because of the
halogen cycle.

As far as I have heard, the "one-size-fits-all" rule for non-halogen
incandescents is at least roughly:

Light output - proportional to voltage to the 3.4 or 3.5 power.

Keep in mind that this exponent varies a little inversely with ratio of
applied voltage to rated voltage.

As for halogen - I would say slightly lower, since higher filament
temperature makes this one lower.
How much lower? I would guess not much if rated life expectancy is at
least 2,000 hours - guesstimate 3.3. But lower than that, closer to 3
even for shorter life ones with color temperature above 3100K - many
automotive headlight bulbs and many stage/studio/photo/projector types.

Life expectancy - It appears to me that the "1-size-fits-all" rule is
inversely proportional to ratio of applied/rated voltage raised to the
12th power.

I would say halogen deviates greatly from non-halogen for undervoltage.
Life expectancy for halogen lamps I would guess mostly increases slightly
to moderately from slight to moderate undervoltage, and can do anything
from great improvement to major disimprovement with severe undervoltage
depending on brand, model, halogen type/concentration details and presence
of contaminants.
But for overvoltage, I would guess that a halogen lamp is more like a
non-halogen incandescent.

- Don Klipstein ([email protected])

 

[ITSME.ULTIMATE]

I would say halogen deviates greatly from non-halogen for undervoltage.
Life expectancy for halogen lamps I would guess mostly increases slightly
to moderately from slight to moderate undervoltage, and can do anything
from great improvement to major disimprovement with severe undervoltage
depending on brand, model, halogen type/concentration details and presence
of contaminants.
But for overvoltage, I would guess that a halogen lamp is more like a
non-halogen incandescent.

- Don Klipstein ([email protected])

Why would higher than rated voltage reducues the life of halogen lamp so
significantly? I thought the reduction in life was due to filament
evaporation and if the halogen cycle returns the tungsten to filament,
why woundn't it offer significantly better life at say 3,400 to 3,500 K?

 

[Victor Roberts]

Why would higher than rated voltage reducues the life of halogen lamp so
significantly? I thought the reduction in life was due to filament
evaporation and if the halogen cycle returns the tungsten to filament,
why woundn't it offer significantly better life at say 3,400 to 3,500 K?

The halogen cycle does not selectively return tungsten to
that portion of the filament from which it evaporated. That
is an old myth. The halogen cycle improves life and
performance through two mechanisms:

1) The high pressure slows evaporation of tungsten - this
improves life.

2) The halogen cleans deposited tungsten from the walls of
the filament tube - which must be close to the filament
since the arc tube must be small to reduce the total
explosive energy. The halogen cycle improves lumen
maintenance but has no significant impact on filament life.

--
Vic Roberts
http://www.RobertsResearchInc.com
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[Victor Roberts]

I would say halogen deviates greatly from non-halogen for undervoltage.
Life expectancy for halogen lamps I would guess mostly increases slightly
to moderately from slight to moderate undervoltage, and can do anything
from great improvement to major disimprovement with severe undervoltage
depending on brand, model, halogen type/concentration details and presence
of contaminants.

My personal experience using halogen A-line lamps from the
"big three" is that undervoltage does greatly extend life,
though I have data only for one undervoltage ratio.

As we have discussed before in this group, I ran 10
100-watt, 120-volt halogen A-line lamps 66% of rated voltage
and the average lamp life was consistent with the normal
life vs. voltage equation published by the IESNA.

The 10 100-watt, 120-volt halogen lamps that were run at 33%
of rated voltage operated for so many years that the
experiment was shut down before they failed.

--
Vic Roberts
http://www.RobertsResearchInc.com
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site without written permission.

 

[Don Klipstein]

My personal experience using halogen A-line lamps from the
"big three" is that undervoltage does greatly extend life,
though I have data only for one undervoltage ratio.

As we have discussed before in this group, I ran 10
100-watt, 120-volt halogen A-line lamps 66% of rated voltage
and the average lamp life was consistent with the normal
life vs. voltage equation published by the IESNA.

The 10 100-watt, 120-volt halogen lamps that were run at 33%
of rated voltage operated for so many years that the
experiment was shut down before they failed.

Darn... I thought I would have remembered that post!

What brand were these?

Meanwhile, I have had a friend operate a couple Sylvania Capsylites
dimmed by a light dimmer to an extent similar to that achieved with
diodes, so applied voltage was close to 70% of rated. As I remember this,
they lasted a little longer than at full voltage. There were no logs of
runtime kept, but if they had life extension same as non-halogen
incandescents would have achieved, the difference would have been big.

- Don Klipstein ([email protected])

 

[Victor Roberts]

Darn... I thought I would have remembered that post!

What brand were these?

GE, but they may have been 90-watt or whatever GE was
selling as a 100-watt replacement.

Meanwhile, I have had a friend operate a couple Sylvania Capsylites
dimmed by a light dimmer to an extent similar to that achieved with
diodes, so applied voltage was close to 70% of rated. As I remember this,
they lasted a little longer than at full voltage. There were no logs of
runtime kept, but if they had life extension same as non-halogen
incandescents would have achieved, the difference would have been big.

I was also using phase cut dimmers, so I would have expected
the Sylvania to have lasted for a longer time as predicted
by the standard equations. This is a test that we need to
run again!

--
Vic Roberts
http://www.RobertsResearchInc.com
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[Victor Roberts]

As a matter of interest what was the efficacy of these lamps run at 33%
of nominal?

I didn't measure the efficacy. This was only a life test.
But there is no reason why the efficacy should not have
followed the standard IESNA formula.

--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
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This information is provided for educational purposes only.
It may not be used in any publication or posted on any Web
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