Difference between revisions of "Philips HPI-T and HPI-T Plus"

*Typical lifetime of 20.000 to 24.000 hours (only HPI-T lamps)

*Luminous efficacy of 72 to 85 lumens/watt

*Horizontal operating position (all HPI-T lamps)

** Philips SI or compatible parallel ignitor for 5000 Volt pulses (except "S" designated lamps)

Notes:  

* some lamps have an integrated internal starter and do not require an external ignitor, presented with the "S" designation;

* MASTER designation should point at better performing lamps but it is meaningless in this lamp range.

| High light output in very compact package || Serious glare risk especially for uncoated lamps

These high pressure sodium vapour lamps are compact light sources that are viable for wide area lighting. Their poor colour reproduction and large output means that they are entirely suited to outdoor lighting or greenhouses as grow light. Compared with fluorescent lamps they were very compact, having great performance at low temperatures. A very long lifetime, that was around 16 to 25 times higher than tungsten lamps, and almost double that of some fluorescent lamps, meant that these lamps are well suited for use in places where lamp replacement was costly, as in high bay lighting, street lighting, tunnel lighting.  

High pressure sodium lamps had higher light output, almost double, of mercury vapour lamps while having very low quality colour reproduction. This means that mercury vapour lamps were still suited for areas where colour reproduction was moderately important and there was still an advantage from compact light sources. However, street lighting was a very important market as the lamp's efficiency ensured cost savings in labour and electricity use, after the 1970s oil crisis. There were some advances in colour reproduction with different lamp technology but standard lamps were not favourite of industrial, workshop lighting commercial premises. The light spectra was, however, highly beneficial for plant growth.

 

The inherent flicker of mains voltage lamps is very low even with conventional gear due to the fact that a large amount of light happens due to thermal emission and balance of the temperature of internal arc tube. There were some electronic medium frequency gear similar with ones used on fluorescent lamps but they were very costly. However, sodium and metal hallide gears are generally compatible, meaning that most sodium lamps can be easily replaced with compatible wattage metal hallide lamps that have a much better colour appearance, sacrificing some energy efficiency due to different lamp technology. The requirement for ignitors along ballasts while it raises total cost and increases complexity, as well as raising the risk due to passing thousands of volts through some wires, means that fixtures have a clear advantage of maximum useful light and restart in case of power failure in almost one minute.

 

Fixtures are generally compact, considering the light output made available, but are generally heavy due to the bulky electromagnetic gear being used. There are directional and omni-directional fixtures that are suited to various purposes. In street lighting, the well known cobra-head style lamppost was used, and they may still be available for purchase. They were only moderately effective as light covered a large area but a considerable amount of light was lost due to the fixture directing some of it upwards, with no control. Omni-directional fixtures were used in residential areas and parks, where ambience was more important than efficiency. Indoor fixtures were centered on the typical high-bay or low-bay types due to their application in greenhouses where light has to be directed entirely downwards. Other fixtures were compact, having a boxy design, with a symmetrical or asymmetrical lamp placement that was suited for flood lighting. These type of lamps were used outdoor, for floodlighting. There were no home designed fixtures as these lamps were never used in home environments.

HPI-T lamps are much more effective for flood lighting but they require specific fixtures and have higher surface temperature, making them more susceptible to damage when improperly handled. Chinese branded lamps are much worse in all performance and quality metrics with shorter useful life, worse colour reproduction and and efficiency as a proper, stable mix of hallides required huge research investment that was too costly for Chinese producers.

The best choice are, probably, the 250 watt lamps as larger powered lamps are too powerful for most purposes. This lamp wattage was also cheaper as they were highly popular. Electro-magnetic ballasts or conventional gears are plentiful and can be used interchangeably with all manufactured lamps for a specific wattage and ignitors' performance is less critical as on high pressure sodium lamps. Lower rated power output gears can be used, but it is not recommended as colour reproduction and lamp lifetime will be reduced while higher powered ones damage the lamp due to over-stressing and is highly dangerous.