Difference between revisions of "Philips Master SDW-T"

The lamp technology was an improvement of previous lamps that were used in larger luminaries, the low pressure sodium types. Looking similar to fluorescent lamps, sodium lamps had a totally different operation. They output monochromatic lamps compared with a pleasant fluorescent white light but they were very well suited for traffic as this light was very little affected by fog and contrast was perfect on roads. Very poor colour reproduction was a very important limitation in market adoption, and it was noticed that increasing sodium pressure broadened light spectra contributing reds and greens to the light output. Many years there was no stable arc tube material that was able to withstand high temperature and aggressive sodium.  

When a suitable ceramic arc tube was developed and manufactured the lamp's high performance was confirmed in applications. Early lamps were attempted to be released with no external additional gear but durability was very poor so ignitors were developed for this specific application. The wattage and voltage of sodium lamps was not compatible with mercury lamps so an operational compromise had to be used to allow operation with mercury vapour lamp gear. This was especially important many years ago as mercury lamp installations were dominant. There was also research that culminated in specialty, even higher pressure sodium lamps, that have improved colour reproduction and a pleasant whiter appearance but they were very costly, had a shorter life and efficiency. They were never popular due to fluorescent lamps being much cheaper and easier to use. These lamps can be easily noticed by seeing their rather thicker internal arc tubes or the higher colour temperatures in datasheets.

 

Later developments focused on releasing optimized ballasts and ignitors that followed slender and more efficient internal arc tubes. Efficiency was improved significantly, making 20 to 30 thousands our lifetimes a certainty, increasing servicing intervals, lowering early failures and making high pressure lamps a very reliable lighting system. Electronic gears were not popular due to high costs although they were entirely possible from a technological perspective and they offered simpler wiring along with higher system energy efficiency. Only ignitors made the switch to advanced electronics as they were products with frequent replacements. The last technological advancement was made by using Xenon and removing Mercury from the arc tube, improving lamp life and efficiency but requiring higher starting voltages and new ignitors. These lamps have a few degrees lower colour temperatures expressed in Kelvin.

 

Overall, sodium high pressure lamps, as is the case of metal hallide lamps, differ very much in terms of performance, even for similar types. Using a datasheet is mandatory if the circuit diagram and lamp being used is not the one that was supplied with the fixture, making operation and servicing a higher skilled job than with previous mercury vapour lamps. Modularity was ensured by making whole fixtures easy to replace and restricting servicing, including cleaning, to offsite premises, avoiding electrocution and prolonged labour at height risks.