white sodium discharge light (SON)

[andrew]

Thanks Adam, you are spot on for usage and thanks Terry; so it seems worth a shot then.

Happy New year all

AJH

[furles]

These don't sound like White Son, which are made in low Wattages, are expensive, use special (expensive) control gear, and have a shorter life than most other types of discharge lamps, are less efficient than most other types and so are unlikely to be used for lighting large outdoor areas. They're quite pink in colour when compared to other 'white' sources, around 2500K. The largest ones now made by Philips are 100W, they used to make a 150W one; I'm not sure what sizes the Iwasaki ones come in. The larger ones, now discontinued by Philips, did see very limited use in streetlighting, in small lanterns on low coumns, mainly in pedestrianised shopping areas.

They were never very widely used, and are now rare, having largely been replaced by low-Wattage ceramic metal halide. They were mainly used indoors; Burger King at Charing Cross Station I London had a few, as did some Safeway Supermarkets, but all of the ones which I saw have now been replaced. For some reason the Philips ones were marked 'Not to be sold in the USA'. They used a magnetic ballast combined with an electronic controller which kept the current within very close limits, and also served s an ignitor. Conventional SON ignitors for small lamps (~2.3 kV) will not reliably strike these lamps, though they will sometimes do so after several seconds.

The lamps you saw sound more like some sort of metal halide. There are pictures of five different White Son lamps on this page:

arc tubes are similar to conventional ON lamps, but somewhat shorter and fatter the one in my 100W lamp is about 35-40 mm long. The arc tubes in metal halide lamps are quite different, either quartz, which are similar to those in Mercury lamps, though somewhat shorter, or ceramic, which are mainly used in smaller lamps. These arc tubes are made of similar material to the SON ones, but are larger in diameter and much shorter, the length often being only about twice the diameter, sometimes less.

Quartz metal halide:

metal halide: