I do have the same impression (over here - 230V), but thinking of it i seen many lamps burning at slightly different temps, so can't say this is a rule
Generally, i seen more 70W and few 100W lamps looking underpowered, 150W (S56) mostly normal, and more 250W+ lamps overpowered
Few factors that may explain this :
- Most 70W lamps are 70W SON E/I. They are started with an internal glow starter, that pretty much limits the available voltage to 1kV at best, while the "Super" lamps won't even show a flash with 1kV. The lamps could very possibly have really lower pressure than the "Super" lamps
- Most low power lamps are used in footpaths, that could be supplied with quite long underground cables, contributing to voltage drop
- Over here, big transformers (typically 400kVA) supply entire blocks of houses. In a small village, a handful of those transformers could be supplying the entire place. Their voltage might be a bit lowered by general load in the area (this is accounted for - The power company aims to supply 240V, so in reality they end up around 230V after the voltage drops). In contrast, transformers supplying lighting on some intercity road are often the same 400kVA size but supply only the lighting installation, they could be running nearly unloaded. The lighitng installation could be getting 240V+, maybe even 250V in some places
- Maybe some common ballast model is out of spec as a rule ?
Also, there seems to be some regional relation : There are places where HPS lamps look overpowered as a rule, of many different wattages in different luminaires. In Jerusalem for example (lanterns are mostly Thorn Pilote T2 and Schreder Z2 & Z3), all of them look like they are getting atleast some 250..260V instead of the 230. I dont have an explanation but this really stands out
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« Last Edit: March 11, 2018, 02:53:53 PM by Ash »
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