I have 2 lamps by Aura, both are SON, and they both have a triple arc. I found out that 2 of the arcs are for instant restrike, but neither lamp ever uses the 3rd arc. Does anyone know what the 3rd arc is for? Is it as a kind of spare, in case one of the other 2 arcs stop working?
Thanks guys!
Natascha

Are all 3 arctubes the same?
And how they are connected, all in parallel?

If both answers are yes, my guess is, it was an attempt for a true instant restrtike capability even with multiple power dropouts in short succession.
To ensure always at least one tube is within the temperature range able to ignite.
The thing is at first power cut the first tube extinguish, but it is still hot. Second tube ignites and starts to warm up. But when another power cut short after the first one happens, the second tube extinguish, as it is already too hot to restrike instantly. Because too short time after the first interruption, the first tube did not cooled down enough to be able to restrike either, so the 3'rd tube kicks in. Before the 3'rd tube warms up to a temperature it wont be able to restrike, it is way more likely one of the first two had already cooled down so it could be able to take over should another power cur happen. Or the power cut happens so quickly after the previous, so the tube which took over before is still not yet so hot it would be able to restrike again.

Thanks a bunch! I only burned it for a short while, and the 2nd tube took over when I turned it off and on again, but I also burned that one a short while, so I guess the first tube already cooled off.....how do you think I could get the 3rd tube to kick in? Burn long so the 1st gets real hot, then do the same with the 2nd? I'd like to see the 3rd tube burn as well

And yes, the are the same and in parellel

Can you please post a picture of your Aura triple arc lamp? I wasn't aware they made this type of SON lamps...

Hello,
might it bee that the third arc tube in you aura lamp is the ceramic tubing over the connecting wire for the two top arc tubes?

Best regards,

Alex

This is certainly interesting, if such a lamp exists, I'd like to see it. Although it's possible Alex is correct, we'd really need to see it to be sure.

That's what I think too

Hello,
might it bee that the third arc tube in you aura lamp is the ceramic tubing over the connecting wire for the two top arc tubes?

Best regards,

Alex

YES!! I took another look, and you are so right!! One tube (the one which doesn't burn) is definitely whiter than the other two. Why would they put a ceramic layer on the wires in this lamp? Never seen it in any lamp with just one arc tube.

I'll take a picture and post it later today

Why would they put a ceramic layer on the wires in this lamp? Never seen it in any lamp with just one arc tube.

That was done to limit the rate of photoelectron emission from the metal frame. Those negative charges tend to accumulate on the burner, causing sodium ions to be draw from the discharge and into the ceramic wall of the arc tube. Since sodium loss contributes to the lamp voltage rise over time, Aura added the ceramic tube around the frame wire so as to increase the lamp's service life.

Pictures 

Yep, that's a ceramic tube over the frame wire to the top of the two arc tubes.

That was done to limit the rate of photoelectron emission from the metal frame. Those negative charges tend to accumulate on the burner, causing sodium ions to be draw from the discharge and into the ceramic wall of the arc tube. Since sodium loss contributes to the lamp voltage rise over time, Aura added the ceramic tube around the frame wire so as to increase the lamp's service life.

Thanks!

It is most common in MH (of any type), where the sodium tends to attack the quartz and form dark brown stains on it. The primary barrier there is the presence of halogens (mainly iodine in most lamps) reacting with the Na first (forming the inert salt like NaI or so), but some Na ions may escape unreacted and when these hit the quartz, cause that degradation.
When only insulated things are around the arctube (nonconductive surfaces like that ceramic sleeve or a quartz shroud around the arctube, but as well all the metal support hardware which is then isolated from the arctube connections), the photo emission make all those parts positively charged, so form an electric field repelling the unreacted Na+ ions away from the arctube walls.

Thanks a bunch guys!