Difference between revisions of "Philips Master SOX-E and SOX"

Philips Master SOX-E and SOX (view source)

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 This lamp technology was successfully developed in the 1930s and improved upon in later decades. The most important achievements were higher quality arc tubes and gas fillings. The same improvements were made on the outer envelope, ensuring reduced heat losses and sodium retention. The low pressure sodium lamp was actually at the center of development on the much more successful and attractive high pressure sodium lamp, some decades later. This lamp technology has the special distinction of being the most efficient light source ever devised, reaching over 200 luments/watt in the case of the last designs, such as on Philips SOX-E.
-The most important competition, early on, was the incandescent lamp, since its light was warm as well while energy efficiency was much improved. The only drawback that sodium vapour lamps had was the requirement for an additional component, the ballast. In general, due to the warm yellow light, this lamps was highly successful in colder climates such as Great Britain and other northern hemisphere countries. Streetlighting was a very common application. As the oil crisis of the 1970s was taking place, there was a strong demand for improved energy efficiency. One research goal was improving the already successful lamp, reducing heat losses of the lamp, as it was already producing reduced light at low temperatures. Special coatings could be applied on the outer envelope, further reducing heat losses and improving efficiency. Of course, this goal was not very easy to achieve as the coating had to survive long term use, absorb as little light as possible and not affect the appearance of the lamp. Special lamp gears were also designed, that had electronic circuitry. This meant that higher energy efficiency was achievable through a combination of better power management, high frequency operation and smoother starts and warmups, giving rise to SOX-E lamps.
+The most important competition, early on, was the incandescent lamp, since its light was warm as well while energy efficiency was much improved. The only drawback that sodium vapour lamps had was the requirement for an additional component, the ballast. In general, due to the warm yellow light, this lamps was highly successful in colder climates such as Great Britain and other northern hemisphere countries. This lamp technology experienced some competition from mercury vapour lamps early on. While sodium lamps of that time fared slightly better in terms of efficiency, they were shorter lived than their counterparts. To the disadvantage of very poor skin rendition of the mercury vapour lamps, the sodium lamped fared slightly better with its monochromatic light. The only issue that would always remain in this competition is that low pressure sodium lamps were never as compact as mercury vapour ones so more efficient directional lighting could theoretically be achieved with mercury vapour lamps. Of course, this was not realised in practice as the low cost of mercury vapour lamps was also a criteria for fixtures selection which meant that system efficiency was always very poor on mercury vapour and only slightly less so on low pressure sodium lamps.
-The market slowly shrinked as high pressure sodium and metal hallide lamps became successful.
+Streetlighting was a very common application. As the oil crisis of the 1970s was taking place, there was a strong demand for improved energy efficiency. One research goal was improving the already successful lamp, reducing heat losses of the lamp, as it was already producing reduced light at low temperatures. Special coatings could be applied on the outer envelope, further reducing heat losses and improving efficiency. Of course, this goal was not very easy to achieve as the coating had to survive long term use, absorb as little light as possible and not affect the appearance of the lamp. Special lamp gears were also designed, that had electronic circuitry. This meant that higher energy efficiency was achievable through a combination of better power management, high frequency operation and smoother starts and warmups, giving rise to SOX-E lamps.
+The market slowly shrinked, by the late 2000s, as high pressure sodium and metal hallide lamps became successful or when LED lighting became popular. It may seem strange that LED technology replaced the more energy efficient high pressure and low pressure sodium lamps but some aspects have to be considered. A good LED lamp design centers on efficient light distribution, that is almost 99% downwards, right from the light source. A typical lamp fixture has to compromise on lamps that are generating light almost omnidirectional or slightly directional, as in the case of low pressure sodium lamps. If the fixture's diffuser is not maintained in a clean state and if water, dirt may get inside the fixture, as it commonly happens, the lighting system efficiency is also reduced. In practice, only about 60% of the designed light reaches the desired target with a new lamp and a 5-7 year old fixture. LED lighting fixtures can maintain virtually all the initial light output efficiency, as the very compact lens system is entirely sealed and remains sealed for the entire lamp life.
- was an improvement of previously developed high pressure sodium lamps, in the early 70s. It was noticed that increasing the pressure of sodium vapours in a discharge improves light output by creating a spectrum that is more appealing. As the emission broadens to reds and greens, colour reproduction improves tremendously, while efficiency slightly drops. Of course, highly resistant ceramic tubes had to be used to contain the sodium vapour discharge and its intensity. Both heat and the corrosive, permeating nature of sodium pose challenges to long service life and good operation. In order to further increase pressure and temperature to improve colour rendering the discharge tube is broadened and shortened. This increases the intensity of the discharge but increases thermal and electrical losses of electrodes and the design of the lamp gets more complex. As usual, sodium still leaks out of the discharge tube at high temperatures so the lamp design had to compensate for these losses with a special construction and gas filling. All these requirements meant that producing such a lamp was highly costly and good manufacturing consistency was mandatory.
-The market for such lamps was small, favouring some indoor aplications especially in colder climate countries such as Great Britain, where sodium lamps were already appreciated. In commercial applications they were more successful when the typical tungsten halogen lamps very low energy efficiency and simple use was no longer acceptable, in late 90s and early 2000s. Development of improved arc tubes was still possible but was considered not viable as the market was not expanding to cover such research and production expenses compared with the more flexible application compact ceramic metal hallide lamps. These lamps were much more energy expansion and have much broader appeal than high pressure sodium lamps.
 == Manufacturing specificities ==