dor123
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In this video George turned on his Sylvania SHP-TS mercury free HPS lamp. However, the lamp cycles in this video, despite it don't have mercury. Can really mercury free HPS lamp cycle at EOL? Or what can cause mercury free HPS lamp to cycle?
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dor123
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I"m don't speak English well, and rely on online translating to write in this site.
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I only working with the international date format (dd.mm.yyyy).
I lives in Israel, which is a 220-240V, 50hz country.
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dor123
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I lives in Israel, which is a 220-240V, 50hz country.
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James
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| Normally not so soon as a regular HPS lamp. But if they live long enough for the arc tube to become severely blackened and raise the sodium vapour pressure and lamp voltage, I cannot exclude that it might be possible. Especially if combined with dips in the mains voltage.
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dor123
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| But the sodium is lost from the arctube as the lamp age. This is the cause of regular HPS lamps to become redder during life. Not?
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Medved
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| There are two mechanisms at play: Arctube blackening (leads to cycling by itself) and sodium loss (does not lead to cycling by itself). Depends which is faster, so dominant at certain point of age, the lamp will or will not become a cycler before it gets replaced.
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No more selfballasted c***
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James
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| It is the presence of mercury that generates the redder light in an HPS (or metal halide lamp). Of course not from spectral radiation of the mercury itself, but increased mercury pressure influences the spectrum of sodium such that it becomes broader (similar to how raising the sodium vapour pressure alone broadens its spectrum). However, the influence of mercury is not symmetric - it only broadens the spectrum on one side towards the red wavelengths. It also causes a sharp rise in lamp voltage.
Since mercury is not lost from an HPS lamp during life, the % mercury : sodium ratio rises so the relative mercury vapour pressure rises during life (due to sodium decreasing). Moreover as the arc tube blackens it traps more heat which amplifies the relative increase of mercury vapour pressure. This is the mechanism by which standard HPS lamps become redder during life.
With Hg-free HPS that cannot happen of course. But there is also an interaction with Xenon. In the plasma, sodium-xenon quasi-molecules are formed and their radiation is principally in a narrow green band which you can see on the short wavelength wing of any HPS spectrum containing Xenon. It is somewhat more significant with Hg-free lamps only because there is no red-broadening due to presence of mercury. As pure Na:Xe lamps age, there is of course a relative shift in the Na:Xe pressures and this also has electrical and spectral influences, but far less than with mercury.
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dor123
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Normally not so soon as a regular HPS lamp. But if they live long enough for the arc tube to become severely blackened and raise the sodium vapour pressure and lamp voltage, I cannot exclude that it might be possible. Especially if combined with dips in the mains voltage.
@James: Isn't this is the mechanism that causes MH lamps to cycle as well? |
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James
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| MH lamps do not cycle, or only under extremely rare conditions. Cycling is an almost unique HPS phenomenon
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RRK
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| Actually I have a couple of well-worn 70W MH lamps, that do cycle. Though, such heavily used that burners are blackened and eroded, one (Osram Excellence) has a dead electrode, the other (very old tin-based Osram in Rx7s) developed a leak into the outer bulb, but burner still ignites. Both cycle on a magnetic choke, so it is definitely not a ballast EOL protection algorithm kicking in.
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dor123
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I only working with the international date format (dd.mm.yyyy).
I lives in Israel, which is a 220-240V, 50hz country.
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trojmiejski
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But there is also an interaction with Xenon. In the plasma, sodium-xenon quasi-molecules are formed and their radiation is principally in a narrow green band which you can see on the short wavelength wing of any HPS spectrum containing Xenon.
Recently I've seen standard Philips SON-T PIA that emitted lemon yellow similar to Hg Free lamps yet SON-T PIA contains some mercury. I suspect the lamps are well used. Looking at the spectrum one thing I've noticed is that sodium gap is wide so sodium pressure is increased. Another thing is significant and quite smooth emission in green part. Could this be the sodium-xenon interaction? Here's the spectrum capture: https://www.lighting-gallery.net/gallery/displayimage.php?pos=-251657 |
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dor123
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@trojmiejski: I think it was a Philips SON-T Pia Plus HG free. If you want to read the etch on the lamp, you need a large optical zoom and a very good contrast, and even than this don't always helps. I've seen the color of the regular Philips SON-T Pia Plus, it isn't as yellow.
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I"m don't speak English well, and rely on online translating to write in this site.
Please forgive me if my choice of my words looks like offensive, while that isn't my intention.
I only working with the international date format (dd.mm.yyyy).
I lives in Israel, which is a 220-240V, 50hz country.
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trojmiejski
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| I captured the etch, nothing about being Hg Free was written on it. Etch was same as standard PIA Plus. I guess the lamp is well used so Na pressure increased. There were others like that and some of them shimmered, the arc wasn't stable.
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trojmiejski
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I went back to older photos on my hard drive and found an extreme example of HPS that just before EOL it went from orange to warm white due to sodium vapour pressure increase: https://www.lighting-gallery.net/gallery/displayimage.php?pos=-252340 |
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