Running at half the voltage

running

full

A faulty assumption doesn't bode well for any conclusions drawn.

It must be *really* dimmed, unless it's also run for some hours at full power. Every halogen I've dimmed has turned black after some time.

full

It makes a difference.

Does anyone ACTUALLY READ WHAT IS POSTED? And THINK about it? Why is it necessary to explain something in excruciating detail over and over and over again?

"William Sommerwerck"

"William Sommerwerck"

How about YOU read it and THINK about it -

instead of childishly stamping your stupid fat feet all over the place.

.... Phil

"William Sommerwerck"

If you'd been paying attention, you'd have seen that his most-recent remark (above), though correct /out of context/, has nothing to do with the issue at hand.

Because people keep making the same illogical claims?

"William Sommerwerck""

There are actually two issues.

One... A halogen lamp has to run at or above the temperature at which the tungsten is redeposited on the filament more rapidly than it evaporates. This temperature is presumably well-above the temperature of a conventional incandescent lamp. It's reasonable to assume that reducing the filament voltage some unstated amount will lower the temperature below the critical recycling temperature, but still high enough to cause the filament to rapidly burn out. No one here seems to have any information about this.

Two... "Obviously", if the filament voltage is "low enough", the rate of tungsten evaporation will be so low, that it doesn't matter whether the lamp is conventional or halogen.

These have nothing to do with each other, as the temperature for One is almost certainly well above the temperature for Two.

This is what Wikipedia has to say. (The following is 100% accurate and unimpeachable, of course.)

"Halogen lamps are manufactured with enough halogen to match the rate of tungsten evaporation at their design voltage. Increasing the applied voltage increases the rate of evaporation, so at some point there may be insufficient halogen and the lamp goes black. Over-voltage operation is not generally recommended. With a reduced voltage the evaporation is lower and there may be too much halogen, which can lead to abnormal failure. At much lower voltages, the bulb temperature may be too low to support the halogen cycle, but by this time the evaporation rate is too low for the bulb to blacken significantly. There are many situations where halogen lamps are dimmed successfully. However, lamp life may not be extended as much as predicted. The life span on dimming depends on lamp construction, the halogen additive used and whether dimming is normally expected for this type."

The article says that the first halogen lamps (for a carbon filament) were patented in 1882.

The title of this thread is "Running at half the voltage."

"William Sommerwerck"

The TRUTH is that the re-deposited metal does NOT repair the damage done to the filament - there are many pics that show this.

The halogen cycle merely keeps the quartz glass clean !!

And the one thing that matters most is the GAUGE of the wire in the filament.

Most halogen lamps are LOW voltage, hence THICK filaments - leading to longer life than for high voltage ( ie 120V /240V) lamps of the same power.

It is sooooooo simple - if the surface temp is the same but there is way more material then it takes longer for the filament to wear out.

.... Phil

You're right about the halogen being there to keep the glass clean, but not about the longer life. A 3400K mogul-base photoflood, like the ones I used to use in the 1970s, has a lifetime of about 25 hours.

The high gas pressure inside quartz-halogen bulbs is what requires the very thick quartz envelopes. High pressure slows down the diffusion of tungsten vapour away from the hot spots, so that metal is selectively redeposited near where it evaporated. That improves the lifetime by a pretty useful factor like 20, and that's apples-to-apples, both 120V 500W.

Cheers

Phil Hobbs

What is that supposed to prove ? ?

Is that not a 120V quartz-halogen lamp ???

A 24V, 150W, 3300K QI ( 35mm slide) projector lamp has a rated life of 50 hours.

Such lamps have been in use common since the late 1960s.

It is NOT in the SAME places and huge gaps open up.

See the pics on Wiki.

.... Phil

I won't gainsay any of your other remarks. But I've seen this.

"William Sommerwerck"

Proves nothing.

.... Phil

No, it's apples-to-apples, as I said. The mogul-base floods were just like really big, ordinary incandescents. Thin glass, low pressure argon fill. No quartz, no halogen. The envelopes got black really fast, even though they were much larger than normal medium-base bulbs.

It isn't a perfect solution, because otherwise the bulb would never fail. So what? The numbers are as I posted--about a 20x lifetime increase.

You're out of your depth on this one, Phil.

Cheers

Phil Hobbs

For various values of "successfully", perhaps.

Other remarks? Where? You've seen them ALL? I'm impressed.

D*****ad.

What a pathetic fake and damn liar.

F*ck off.

.... Phil

Lies will get you nowhere, Phyllis.