Difference between revisions of "Osram HWL"

*Soft glass (100, 160 and 250W) or Hard glass (250 and 500W) bulb

*Typical lifetime of 10.000 (most lamps) to 13.000 hours (only 160W lamp)

*Luminous efficacy of 11 to 25 lumens/watt (highest on highest wattage lamps)

*Warm white colour designation (3300 to 3700K colour temperature)

[[Image:Philips HPL-N 250W.jpg|Philips ML 250W]]

The ML lamps is highly similar to standard high pressure mercury vapour lamps. It can be used on indoor as well as outdoor lighting. However, there are some differences. Due to the way the lamp operates it is very well suited for indoor lighting, being quite well suited for living room lighting. The warm colour appearance and good colour reproduction does not detract too much from a typical fluorescent lamp. While it does highlight greens and blues, the light is quite well balanced. Flickering is present but much reduced compared with high pressure discharge lamps. Garden and animal lighting is also possible with very good results, as well as indoor plant showcasing. In these applications the lamp's heat output and spectra can be used with good results although present LED lamp technology is much more energy efficient. The lamp is highly useful also during renovation work or as general lighting in attics, due to the light output and pleasant appearance.

Philips ML or mixed-light is highly user friendly as the lamp is very easy to use if you have the mains voltage required by the lamp. The product does not require any gear to work, being usable directly connected to the mains as any tungsten, compact fluorescent or led lamp with screw base. The only major precaution is avoiding direct water splashes and mounting positions that deviate too much from vertical base up or down positioning. An inappropriate lamp mounting is not dangerous but makes the lamp cycle stopping and restarting, especially in warm areas. Closed fixtures are not optimal as the lamp generates releases quite a lot of heat. Care should also be taken as the lamp's life is even more affected by frequent starts and strong vibrations, so continuous use is advised.

| ML 100W E27 225-235V SLV || E27 || 100 W || 1100 lm || Cool White ||  3300 K || 72 || 10000 hours

| ML 160W E27 225-235V SLV || E27 || 160 W || 3200 lm || Cool White || 3600 K || 65 || 13000 hours

| ML 250W E27 225-235V SG SLV || E27 || 250 W || 5500 lm || Cool White || 3400 K || 65 || 10000 hours

| ML 500W E40 225-235V HG SLV || E40 || 500 W || 13000 lm || Cool White || 3700 K || 50 || 10000 hours

All the above particular operating issues make the lamp slightly inconvenient to operate, even if the lamp itself is highly attractive to use and install and not an expensive purchase. Failing lamps can be easily determined by the lengthened time of restart in case of power being cut off and then resumed. A longer than typical time and less definite starting after cooldown, meaning more failed attempts at restarting than 1 or 2, point to a worn of lamp that will soon be dead. Of course, as mentioned before, this should be tested with the same straight vertical position. However, as lamps age, they will be more sensitive to voltage, accumulated heat nearby the lamp than newer ones so actual service life can be severely reduced compared with what the datasheet may suggest.

| Moderate light output, comfortable white light || Sensitive to switching

| Good for living room and garden lighting || Not very powerful

Slightly major drawbacks are the lamp's sensitivity to positioning and operating voltage, along with slightly lower than average service life, especially compared with modern lighting technology. The lamp's low efficiency is caused by the compromise of its internal construction. The warm light generated by the internal filament also comes with massive heat radiation, which is similar to typical tungsten lamps that were previously popular. It should be noted that, due to the lamp's construction, light output is not uniform, with noticeable segregation in colour and intensity between the center and tip of the lamp. Although this effect is not severe, it may be a slightly unpleasant effect in certain situations.

The pleasant light is suited both as general lighting in homes as well as gardens or workshops. A good selection of lamps can be used if power consumption is not critical and a specific scene or effect is desirable. Unfortunately, especially in small spaces, the lamp can contribute to heating, which may be advantageous as well as undesirable, depending on application. Special care should be taken when cleaning the lamp as vibrations, dirt accumulation and improper handling can easily crack the bulb, especially on soft glass lamps. Any dirt present on the lamp may be trapped longer due to melting and subsequent adhesion to glass. This means that lamp cleaning has to be as thorough and careful as on old tungsten lamps. While the lamp has a very high output when started and slowly reduces on warm-up, with a corresponding change in light colour, it is not unpleasant. At the beginning most light is output by the internal incandescent filament rather than the mercury discharge. Lamp restart in case of failure occurs in less than 2 minutes and is less unpleasant than on other high pressure discharge lamps.

This type of mercury vapour lamps were popular mostly before the oil crisis that occurred in the 1970s. Many years have passed since use of this lamp was basically non existent, meaning that stocks are not very large. Although the lamp could directly replace even less efficient tungsten or incandescent lamps, this market very rapidly diminished as soon as compact fluorescent lamps with screw bases were made available. These had a much longer life, had no restriction on mounting, were highly energy efficient and had even better colour reproduction. There were few fixtures specifically designed for Philips ML lamps. They could operate on typical high pressure mercury vapour fixture but this was uncommon. There was a market for street-lighting in France, many decades ago, as the lamp offered a pleasant light and energy was quite cheap. Due to the lamp operating restrictions as well as simple use, free standing or hanging mounting were quite common, even if lighting efficiency was diminished.

The best lamps in terms of useful lifetime, colour reproduction, light output, are the equivalent OSRAM HWL branded lamps, not Philips ML lamps even if Philips lamps were very popular. Chinese branded lamps are much worse in all performance and quality metrics with a greener light output and poor reproduction of oranges and reds. The Philips lamps lacked high quality coatings, especially in newer lamps, so lighting quality and colour reproduction was slightly affected.

The best choice of wattage are the 160 and 250 watt lamps as the 100W lamp has low light output and efficiency. The 100W lamp is a strange case of a design that is even less efficient at lighting than a typical 100W incandescent lamp, due to compromises in the mixed lightin lamp design. Higher power rated lamps, such as the 500W were more efficient but the lamp's size clearly was a major disadvantage. In such situations a typical standard high pressure mercury vapour lamp with half power rating oferred much better efficiency despite requiring a bulky electromagnetic ballast.

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.