Difference between revisions of "Philips ML"

ML lamps are slightly adapted high pressure mercury vapour lamps. They were originally designed to address the requirement of better colour reproduction compared with a bare mercury vapour lamp. While they did severly improve red output of the installation, efficiency was also reduced, since this additional light was created less efficiently with the thermal radiation of the internal fillament. Until the advent of suitable internal coatings on standard mercury vapour lamps, this mixed light lamp was also easy to use as there was no requirement for complex wiring, mounting and servicing of ballasts as well as lamps. As most light fixtures were using large wattage incandescent lamps, the Philips ML lamps were very easy to retrofit and for many decades this was a simple light upgrade. Of course, there were many improvements on lamp technology but the same benefits were kept along usability and lower maintenance due to less frequent lamp changing.

Internal coatings were introduced on the entire lamp range in the 1980s although they were present even as early as 1950s on these mixed light lamp types. Coating were useful to make the beam pattern more uniform and there were many benefits to having a coating as the two internal light sources had slighly different patterns. Of course, coatings were useful if flourescent powders were used, but this increased the lamp cost and provided small improvements as light absorbtion, wear had to be very low. Also, light improvement was much reduced compared with a typically sized mercury vapour lamp due to less UV light being generated by the discharge tube. The advent of improved discharge tubes that were made of quartz instead of glass improved efficiency but results were not as large as on standard mercury vapour lamps. Major efficiency increases were, however, centered on lower powered lamps, as they could not be have the required balance of pressure and temperature to achive optimal results.

Although important, the introduction of internal coatings did not have the same impact as on standard mercury vapour lamps. For many years the lamp had to be specifically designed to acomodate filaments as well as the heat being released. The coating itself does not contribute much to the light output as the mercury vapour discharge tube is smaller and has less UV output than a typically sized lamp. As a matter of fact, for a typical power rating, around half the wattage is used by the filament and the other half by the mercury vapour discharge tube. This is mostly due to the compromise of achieving a better colour reproduction than a typical standard mercury vapour lamp and this required more useful light released by the incandescent coil. Of course, better efficiency can be achieved with filaments that do not run as hot and with more light output from the mercury vapour discharge but most longtime manufactured lamps, including the Philips ML, aimed at better comfort and had to accept less efficiency.