Why SBMV lamps, start to cycle when burned horizontally? « on: January 29, 2016, 08:46:23 AM » Author: dor123
Why SBMV lamps, start to cycle when burned horizontally, while regular MV lamps don't do this?
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	Re: Why SBMV lamps, start to cycle when burned horizontally? « Reply #2 on: January 29, 2016, 01:41:19 PM » Author: dor123
I've even managed to repate this phenomenon myself, when did this .
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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.

	Re: Why SBMV lamps, start to cycle when burned horizontally? « Reply #3 on: January 29, 2016, 03:19:28 PM » Author: Medved
all SBMV's I know are designed for vertical position only. If you burn such lamp horizontally, the heat from the ballast rises towards the arctube and that is overheating, yielding to a bit higher gas pressure (it is just the gas attempting to expand, so less sensitive to heat than with saturated vapor lamps, but the heat is way greater than just a blackened arctube). The result is the arc voltage drop rises, and it becomes even more difficult to reignite after the current zero crossing (that is already marginal due to the resistive ballast nature - with rather long gap without any current), till at one moment the arc does not reignite again. Of course the filament section above the arctube becomes overheated as well and that part then degrade way quicker than ratng even without the cycling problem. Generally it is not good idea at all to attempt to operate the SBMV off the vertical position, it's life would be shortened very significantly.
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	Re: Why SBMV lamps, start to cycle when burned horizontally? « Reply #4 on: January 29, 2016, 10:22:00 PM » Author: dor123
Thanks Medved.
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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.

	Re: Why SBMV lamps, start to cycle when burned horizontally? « Reply #5 on: January 30, 2016, 04:25:30 AM » Author: dor123
This is a bit strange. During the end of the 90's, when SBMV lamps were very popular in Israel, these lamps sometimes found also in floodlights and streetlights (When they burning horizontally), and they didn't cycle at all.
« Last Edit: January 30, 2016, 04:40:37 AM by dor123 »		Logged

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.

	Re: Why SBMV lamps, start to cycle when burned horizontally? « Reply #6 on: January 30, 2016, 09:24:37 AM » Author: Medved
It may depend on the design of the actual lamp, on it's state or even on it's exact position. I know Philips lamps had the filament placed very close to the crown of the bulb, so when horizontally, the heated gas will miss most of the arctube. Or when the filament happens to be positioned so the "missing section" of the circle formed by the filament (it is usually a "C" shape) is below the arctube, the hot gas flow may miss the arctube as well. In any way the lifetime and/or reliability of such operated lamps is quite severely compromised: Heated gas (either from the other filament section or from the arctube) reaching other parts of the filament cause that section to overheating and so evaporate way faster than designed, yielding a premature filament fail. The outer glass is too close to the filament on the side, so becomes overheated as well, yielding too high thermal differences, so stress within the material (normally the hot gas is supposed to rise towards the crown or base of the bulb, sections further away from the hat sources, so not exposed that much by the IR heat transfer) And someone knowing better the details of designing a SBMV will for sure list many other weak points.
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	Re: Why SBMV lamps, start to cycle when burned horizontally? « Reply #7 on: January 30, 2016, 02:02:01 PM » Author: Roi_hartmann
I have very little real life experience with high wattage SBMVs but I've always had the impression that only small wattage SBMV lamps have to be used vertically and bigger ones have free burning position.
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	Re: Why SBMV lamps, start to cycle when burned horizontally? « Reply #9 on: February 13, 2016, 12:29:54 AM » Author: arcblue
I didn't know SBMVs were supposed to be used only in a vertical position. None of my lamp catalogs or EYE lighting spec sheets seem to indicate a burning position restriction. I've been running an unknown brand 160w clear SBMV (might be a PlusRite) in a work light fixture horizontally for years (though it probably only has a few hundred hours on it). It doesn't ever cycle and it still works fine. But the upper part of the arc tube and the inside of the bulb envelope have darkened from filament evaporation (which I assumed was due to it being a low-quality bulb). I took it out yesterday and reinstalled it in a different fixture, base down and it cycled a few times before staying lit when first turned on. I've remembered this from before - it didn't like having its burning position changed. It seems to have something to do with the bimetal switch working differently in different positions.
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