Hi everyone,

I have a regular GE 35W Lucalox high pressure sodium (2,000K) from the States and I was wondering if anyone knows:

What prevents me from driving it slightly above its nominal, to make it look like a SDW white high pressure sodium?

I usually under-drive it at apprx 20W (0.37A) and 30W (0.43A) (these are with fluorescent ballasts, so they are not a perfect match in Watts)

Do the SDW have a more special design (seals/amalgam, etc) that allows them to be pushed to 2,400-2,600K?

I can arrange my ballasts for the Lucalox to be pushed around 50-80W (0.80+A)

I imagine this will affect lamp life, but what are the main disadvantages in doing so?

I am not burning it in excess in hours, so imagine something like 2-3 hours a day.

Many thanks!
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UVIR ( )

The SDW lamps have generally thicker arctube, so the arctube material is further away from the arc. When you overdrive the regular HPS, the narrower arctube means it's material will operate at higher temperature than designed, so degrading faster (and so failing earlier).
Second problem could be the thermal stability of the system - the overheated burner will have greater tendencies towards thermal runaway (elevated temperature causes higher voltage drop, so higher power delivered to the lamp, so increasing the temperature further) on common characteristic ballasts. This leads to not as good color stability or when really strong, to the point when the arc voltage exceeds the capability of the ballast to hold an arc, so extinguish after a while. That then means lamp cycling.

As far as I know, only Iwasaki was able to finetune their white HPS lamps so, they suffice with regular gear, Philips lamps need special arctube temperature stabilizing electronic.
With a regular HPS operated at such high temperatures I would expect it will require such stabilizer as well, but the problem is, it's properties are different than the commercial white HPS, so the available stabilizers won't match.

So you may try, but expect problems with really short life, poor color stability (and repeatability when you e.g. replace the lamp) or even lamp cycling.

If it is in fact a US lamp, it can be driven on a 50w ballast producing color close to incandescent. I tried this awhile back and the lamp (A GE Lucalox 35w) actually lasted surprisingly long for overdriving it 20w