Archived from groups: comp.sys.ibm.pc.hardware.chips,comp.sys.intel (More info?)
In line comments.
Stuart
"Robert Redelmeier" <redelm@ev1.net.invalid> wrote in message news:rGBDd.12106$wi2.11128@newssvr11.news.prodigy.com...
> In comp.sys.ibm.pc.hardware.chips Stuart <xyz@hotmail.com> wrote:
>> In fact the life of a light bulb depends
>
> Of course.
>
>> In unusual conditions such as a 135 volt lamp burning
>> continuously at 115 to 120 volts several years is not unusual.
>
> 20,000 hrs? I would have thought tungsten sublimation
> would have killed a std 135V/2000h bulb long before then.
> Unusual conditions like halogen fill for redeposition?
Just standard US lamps except for the 135 volt.
In the cases I was referring to they are in difficult places to reach and are not turned off.
>
>> In more extreme circumstances such as a 230 volt lamp operated
>> at 125 volts for use as an indicator (as opposed to providing
>> illumination) with a limited number (less than 5) of on/off
>> cycles per year the life is in the twenty to thirty year range.
>
> I've run Euro bulbs. They hardly give off enough light at
> 115V to qualify as indicators except in darkened surroundings.
I can only say that my former employer used/uses them in hundreds of installations and they do the job.
>
> I didn't think cycles mattered that much on tungsten-filament
> bulbs with good design for thermal expansion & filament
> support. Las Vegas signage certainly gets hammered.
In a standard lamp operated at its design voltage lamp on/off cycles are a major factor in lamp failure.
You may have noticed that most lamps fail when you turn them off.
As to Las Vegas I have no personal knowledge but I do know that lamps used for traffic signals are of special construction.
They have limitations such as "Burn base down to horizontal" and have, relatively, a low light output, i.e., a 100 Watt traffic signal bulb lamp delivers a light output approximately equivalent to a 60-75 watt normal lamp. As a side note, the local jurisdictions are on a program to replace the lamps in traffic signals with LED arrays. They state the savings in lamp replacement labor costs and energy costs will offset the higher original cost.
>
>> In contrast a photo flood lamp under normal use is
>> rated in tens of hours.
>
> Of course. So do Japanese 100V bulbs at 115V. Voltage ratings
> are a bit of a farce. Filaments have a resistance curve and
> reach a particular temperature at a given voltage.
>
Voltage ratings are the result of a design tradeoff.
For a given physical lamp if you lower the voltage you will lower the light output and the efficiency and increase the light output because, as you state, the filament is at a lower temperature.
Conversely, if you raise the voltage the temperature increases, the light output and efficiency increase and the life decreases.
The voltage rating assigned to the physical lamp is, more or less, a marketing decision balancing the cost of manufacture, the cost to produce a lumen and customer expectations as to light output, life, and purchase price.
> -- Robert
>
In line comments.
Stuart
"Robert Redelmeier" <redelm@ev1.net.invalid> wrote in message news:rGBDd.12106$wi2.11128@newssvr11.news.prodigy.com...
> In comp.sys.ibm.pc.hardware.chips Stuart <xyz@hotmail.com> wrote:
>> In fact the life of a light bulb depends
>
> Of course.
>
>> In unusual conditions such as a 135 volt lamp burning
>> continuously at 115 to 120 volts several years is not unusual.
>
> 20,000 hrs? I would have thought tungsten sublimation
> would have killed a std 135V/2000h bulb long before then.
> Unusual conditions like halogen fill for redeposition?
Just standard US lamps except for the 135 volt.
In the cases I was referring to they are in difficult places to reach and are not turned off.
>
>> In more extreme circumstances such as a 230 volt lamp operated
>> at 125 volts for use as an indicator (as opposed to providing
>> illumination) with a limited number (less than 5) of on/off
>> cycles per year the life is in the twenty to thirty year range.
>
> I've run Euro bulbs. They hardly give off enough light at
> 115V to qualify as indicators except in darkened surroundings.
I can only say that my former employer used/uses them in hundreds of installations and they do the job.
>
> I didn't think cycles mattered that much on tungsten-filament
> bulbs with good design for thermal expansion & filament
> support. Las Vegas signage certainly gets hammered.
In a standard lamp operated at its design voltage lamp on/off cycles are a major factor in lamp failure.
You may have noticed that most lamps fail when you turn them off.
As to Las Vegas I have no personal knowledge but I do know that lamps used for traffic signals are of special construction.
They have limitations such as "Burn base down to horizontal" and have, relatively, a low light output, i.e., a 100 Watt traffic signal bulb lamp delivers a light output approximately equivalent to a 60-75 watt normal lamp. As a side note, the local jurisdictions are on a program to replace the lamps in traffic signals with LED arrays. They state the savings in lamp replacement labor costs and energy costs will offset the higher original cost.
>
>> In contrast a photo flood lamp under normal use is
>> rated in tens of hours.
>
> Of course. So do Japanese 100V bulbs at 115V. Voltage ratings
> are a bit of a farce. Filaments have a resistance curve and
> reach a particular temperature at a given voltage.
>
Voltage ratings are the result of a design tradeoff.
For a given physical lamp if you lower the voltage you will lower the light output and the efficiency and increase the light output because, as you state, the filament is at a lower temperature.
Conversely, if you raise the voltage the temperature increases, the light output and efficiency increase and the life decreases.
The voltage rating assigned to the physical lamp is, more or less, a marketing decision balancing the cost of manufacture, the cost to produce a lumen and customer expectations as to light output, life, and purchase price.
> -- Robert
>