waynejitsu
Enlightened
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- Sep 10, 2006
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Can a bulb be damaged or have a lower life by underpowering?
If yes, by how much?
Thanks for any info!
If yes, by how much?
Thanks for any info!
bulb damage by low power???
- Thread starter waynejitsu
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jrmcferren
Enlightened
If it is a standard incandescent, you risk nothing other than output by running the lamp undervoltage. The only issue (as mentioned above) is with halogen. Take a household bulb for example, a 60 watt 130 volt lamp will run at 60 watts and last 1000 hours at full voltage and achieve full output. Take the same lamp run it at 120 volts it will use 52 watts, last 2000 hours and the output is reduced by 15 percent.
An interesting paragraph taken from a Wikipedia article about the incandescent light bulb:
"According to the relationships above (which are probably not accurate for such extreme departures from nominal ratings), operating a 100-watt, 1000-hour, 1700-lumen bulb at half voltage would extend its life to about 65,000,000 hours or over 7000 years – while reducing light output to 160 lumens, about the equivalent of a normal 15 watt bulb. The Guinness Book of World Records states that a fire station in Livermore, California has a light bulb that is said to have been burning continuously for over a century since 1901 (presumably apart from power outages). However, the bulb is powered by only 4 watts. A similar story can be told of a 40-watt bulb in Texas which has been illuminated since September 21, 1908. It once resided in an opera house where notable celebrities stopped to take in its glow, but is now in an area museum."
"According to the relationships above (which are probably not accurate for such extreme departures from nominal ratings), operating a 100-watt, 1000-hour, 1700-lumen bulb at half voltage would extend its life to about 65,000,000 hours or over 7000 years – while reducing light output to 160 lumens, about the equivalent of a normal 15 watt bulb. The Guinness Book of World Records states that a fire station in Livermore, California has a light bulb that is said to have been burning continuously for over a century since 1901 (presumably apart from power outages). However, the bulb is powered by only 4 watts. A similar story can be told of a 40-watt bulb in Texas which has been illuminated since September 21, 1908. It once resided in an opera house where notable celebrities stopped to take in its glow, but is now in an area museum."
winny
Flashlight Enthusiast
Meduza is correct as always. 
When you underdrive an halogen bulb enough, the wall temperature drops so much that the halogen process stops and the bulb starts to blacken. This can be partly or fully reversed by driving the bulb at a higher voltage again (read specified), where the halogen process will suck back the wolfram particles from the glass.
If you keep underdriving it, it will fail within hours or days, not to mention the efficiency drops to just over 0 lm/W due to the blackening.
Non-halogen incandescent lamps does not have this effect at all. You can underpower it as much as you want with no negative effect besides the dropping efficiency.
When you underdrive an halogen bulb enough, the wall temperature drops so much that the halogen process stops and the bulb starts to blacken. This can be partly or fully reversed by driving the bulb at a higher voltage again (read specified), where the halogen process will suck back the wolfram particles from the glass.
If you keep underdriving it, it will fail within hours or days, not to mention the efficiency drops to just over 0 lm/W due to the blackening.
Non-halogen incandescent lamps does not have this effect at all. You can underpower it as much as you want with no negative effect besides the dropping efficiency.
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waynejitsu
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Halogen, ok, got it.
How about Xenon, such as a SF bulb?
Thanks for the help!
How about Xenon, such as a SF bulb?
Thanks for the help!
D MacAlpine
Newly Enlightened
waynejitsu said:
Xenon is a halogen (see also Krypton) - the most commonly used one for high powered lamps I think.
OceanView said:
LEDs are generally more efficient when underdriven (to a point) and less efficient when overdriven.
All incandescent lamps are less efficient when underdriven. Halogens can gain a fair bit in efficiency when overdriven (something like 40% more light when voltage is increased by 10% for only 15% or so more power consumption I think).
If you have a search through the forums you'll find some threads with extensive data on these effects.
jayflash
Flashlight Enthusiast
Overdriving any incandescent lamp increases its efficiency but shortens its life. Xenon filled lamps can and do blacken but the rate is probably influenced by the amount, if any, of halogen also in the gas mix.
I used to use a StreamLight Jr. with fresh alkaline and NiMH cells and the lamps quickly blackened, however, they were not advertised as halogen filled.
Might not the increased filament life of reduced operating voltage offset the reduced or lack of halogen cycle at lower voltages? Of course that doesn't address the blackening issue due to less tungsten recombination.
I used to use a StreamLight Jr. with fresh alkaline and NiMH cells and the lamps quickly blackened, however, they were not advertised as halogen filled.
Might not the increased filament life of reduced operating voltage offset the reduced or lack of halogen cycle at lower voltages? Of course that doesn't address the blackening issue due to less tungsten recombination.
mudman cj
Flashlight Enthusiast
Incandenscents lose efficiency when underpowered because the temperature of the filament decreases, which in turn shifts the emissions spectrum to lower frequencies. Thus, more infrared is produced from the consumed energy and less visible light eminates.
