Lampara sa Tungsten Halogen

Nasod sa 1958, ang E.G. Fridrich ug E.H. Wiley miangkat og Tungsten Halogen Lamp pinaagi sa pag-introduk ng halogen gas (basically Iodine) sa sulod sa incandescent lamp. Sa basic, walay halogen gas, ang incandescent lamp filament gradual nga mawala ang iyang performance tungod sa evaporation sa iyang filament sa mas taas nga temperatura sa operasyon. Ang evaporated tungsten gikan sa filament sa normal incandescent lamp nakapildi sa sulod sa bulb surface gradual. Busa lumens na-obstruct gikan sa iyang direksyon para molabas sa bulb. Busa ang efficacy i.e. lumen/watt sa incandescent lamp mag-uli gradual. Apan ang pag-insertion sa halogen gas sa incandescent lamp naka-overcome kini nga difficulty plus iban pa nga advantages. Tungod kay ang inserted halogen gas makatabang sa evaporated tungsten para maka-form og tungsten halide nga dili nakapildi sa inner bulb surface sa bulb surface temperature sa tulo 500K hangtud 1500K. Busa lumens dili na-obstruct. Busa Lumen per watt sa lamp dili na-deteriorate. Muli tungod sa insertion sa pressurized halogen gas, ang rate sa evaporation sa filament mag-uli.

Ang Working Principle sa Halogen Lamp

Ang working principle sa halogen lamp based sa regenerative cycle sa halogen.

Sa incandescent lamp tungod sa taas nga temperatura tungsten filament ma-evaporate sa panahon sa iyang operasyon. Tungod sa convectional flow sa gas sa sulod sa bulb, ang evaporated tungsten gi-transport away gikan sa filament. Ang wall sa bulb relatively cool. Busa ang evaporated tungsten gi-adhere sa inner bulb wall. Wala kini ang kasinabi kung gamiton ang halogen sama sa iodine sa bulb container. Ang temperatura sa filament sa halogen lamp maintain sa tulo 3300K. Busa diri usab tungsten ma-evaporate gikan sa lamp filament. Tungod sa convectional flow sa gas sa sulod sa bulb, ang evaporated tungsten atoms gi-transport away gikan sa filament sa relatively lower temperature zone diin sila combine sa iodine vapor ug form ang tungsten iodide. Ang temperatura required para sa combination sa tungsten ug iodine 2000K.

Pagkatapos ang same convectional flow sa gas sa sulod sa bulb carries ang tungsten iodide sa wall sa relatively lower temperature. Apan ang bulb designed nga ang temperatura sa glass wall remain sa tulo 500K hangtud 1500K ug sa tulo temperatura tungsten iodide dili adhere sa bulb wall. Gi-return ni sila back sa direction sa filament tungod sa same convectional flow sa gas sa sulod sa bulb. Muli, sa close vicinity sa filament diin ang temperatura mas taas sa 2800K, ang tungsten iodide ma-breakdown sa tungsten ug iodine vapor. Tungod kay ang required temperatura para sa breaking tungsten iodide sa tungsten ug iodine atoms >2800K.

Pagkatapos ang tungsten atoms further proceed ug get re-deposited sa filament para compensate previously vaporized tungsten. Pagkatapos sila again ma-evaporate tungod sa taas nga filament temperature ug become free para acquire iodine para form iodide. Kini nga cycle repeat again and again. Busa ang filament dili permanent ma-evaporate busa ang temperatura sa filament can be maintain sa very high level compared sa normal incandescent lamp nga nagpadako sa iyang efficiency i.e. more lumen/watt rating. Tungod kay wala permanent evaporation sa filament, ang lifespan sa Tungsten Halogen Lamps gets much longer with clarity of illumination. Ang chemical equation is

Construction of Halogen Lamp

Comparing to the halogen lamp, the incandescent lamp is able to provide only 80% of its lumens at the end of the life as the clarity of glass wall becomes fade due to tungsten deposition on it whereas the tungsten halogen lamp is able to provide above 95% of its lumens at the end of life. Previously borosilicate or aluminosilicate glass was used to make bulb of the halogen lamp. Because they have higher temperature withstanding capability and their thermal expansion co-efficient is very low. But now a day’s Quartz is widely used to make halogen bulb glass. Quartz is transparent silica and pure silicon dioxide. It is very stronger and it withstands higher temperature as compared to the borosilicate or alumina silicate glass. Quartz bulb can be soft material above 1900K. Again around the filament 2800K must be maintained to get continuous halogen cycle. So the distance between the filament and quartz bulb wall must be maintained in such a way that the quartz bulb wall gets temperature below 1900K. The bulb wall should be stronger and smaller in volume such that the lamp can be operated at the inner pressure of several atmospheres. Again higher pressure inside the bulb reduces the rate of evaporation of the tungsten filament. A certain amount of nitrogen and argon are mixed in addition to the halogen gas inside the bulb to maintain this higher gas pressure inside. Thus the lamp can be operated at the higher temperature and with higher luminous efficacy for long time. Most of the lamps in present days are with bromine instead of iodine. Bromine is colorless whereas the iodine is purplish tint.

Application of Tungsten halogen lamps

Tungsten halogen lamps can have a number of shapes but they are most often tubular with the filament oriented axially. Again they are available in both double ended and single ended types. Two types are shown below.
Two types are shown below.

Tungsten halogen lamps give correlated color temperature, excellent lumen maintenance and reasonable life. Tungsten halogen lamps are appropriate to be used in outdoor lighting application. Particularly they can be used in the sports lighting, theater, studios and television lighting etc. Their filaments are generally mechanically stable and positioned with higher precision. Tungsten halogen lamps are being used widely as spotlight, film projectors and scientific instruments. Types of Tungsten halogen lamps in the market of low voltage tungsten filament lamps are also available. They are available at 12, 20, 42, 50 and 75 Watts operated between 3000K and 3300K. Their life ranges from 2000 hours to 3500 hours.

As the optical projection equipments the halogen lamps are generally used, in present days, they are being used widely in the display lighting also.
The main part of the tungsten halogen lamp is small tungsten halogen capsule. It is cemented into one piece, all glass reflectors are as the facets for controlling the beam optically. MR-16 lamp has multifaceted reflector with 2 inch diameter. It has slightly higher luminous efficacy than standard voltage incandescent lamps. Their size is smaller also and permit compact fixture.

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