Halogen bulbs have a wide application because of their better lighting characteristics and longer lifespan compared to the incandescent bulbs. We use them for lighting of shops, shoping windows, living spaces, public interiors and exteriors, etc. Under halogen lighting we experiance better colour rendering and more atractive products. The lighting can be spotlight as well as common difuse light, depending on the type of bulb used. Besides longer life the halogen bulbs give more light for the same wattage. There are types for high valtage suply on 240V, but we have on the market low valtage types to be supplied via the low valtage transformer too. Low valtage halogen bulbs give us more freedom in design of lighting instalations due to the smaller size of bulb and lampholder and low valtage.
We are looking forward to your questions and projects to be able to propose the best solutions of lighting in your interiors and exteriors.
Halogen bulbs were invented in 1970s, and have wire filament too, but it is encased inside a much smaller quartz envelope. The gas inside the envelope is also different — it consists of a gas from the halogen group of elements (iodine, bromine, chlorine, fluorine). These gases have a very interesting property: they combine with tungsten vapor. If the temperature is high enough, the halogen gas will combine with tungsten atoms they evaporate and redeposit them on the filament. This recycling process lets the filament last a lot longer. In addition, it is now possible to run the filament hotter (up to 2500C), meaning you get more light per unit of energy. Because the quartz envelope is so close to the filament, it is extremely hot (250C) compared to a normal light bulb. Halogen bulbs are very sensitive to change of voltage and increase of nominal low valtage for 5% results in shortage of the lifespan for 40%. This drastic change is influenced by the fact that the circular halogen process needs controlled temperature. Quartz bulb is very sensitive to direct human touch because the skin traces on the bulb surface can result in bulb explosion when turned on and cause severe injuries.
Main advantages of halogen bulb against incandescent bulb are higher light output (to 25lm/W), longer lifespan (4000-6000h), optimal light control, small size, more constant light flux during the lifespan, higher colour temperature – bright white light of 3000K. There are editions with higher colour temperature (4000-6000K) for special purposes.
New technologies anable aditional increasing of light flux. Application of special infra red coating (IRC) makes possible returning of part of IR emition back to the filament. It is then used for heating the filament and thus decreases the need for electricity. This way the light flux is increased for 30%.
Low voltage halogen bulb
Most used from the halogen family were low voltage halogen bulbs. They are very small in size in comparisson to the incandescent bulb of similar characteristics. But to use that kind of bulbs there has to be a transformer to reduce 240V to 6, 12 or 24V. Typical representative of the family are small low voltage spotlights.
Thanks to small size halogen bulbs are used in small decorative lighting fixtures as just bulb or bulb with reflector. Standard types of spotlight bulbs use dichroic mirror that directs 2/3 of IR radiation to the back and just 1/3 of heat to the lit object. The heat produced by halogen bulbs is still very high and it influences the construction of the luminaire. Bulbs with aluminium reflector are used in cases where cooling of the bulb is problem or it is impossible. The bulb has to be cooled properly otherwise the lifespan that was described as advantage shortens drastically. Besides that there is negative thermal impact to contacts in the lampholder and insulation sheeting of the wire.
High voltage halogen bulb
Since last few years we have high voltage halogen bulbs on the market. The are offered as a direct substitution to incandescent bulbs. They have the same advantages and disadvantages like low voltage halogen bulbs, but without the transformer in the circuit.
Metal halide bulbs
Metal halide bulbs have extraordinary characteristics regarding light output and quality. Higher light flux is a direct result of high intensiti discharge inside the bulb under high presure. As they need to cool down before reuse the only disadvantage is that we can not use them in on-off scenarios because they have to cool down before reuse. They are seldom used for domestic lighting, but very often we can find them in shops and shoping windows, exterior lighting, special projectors and light efects.
Over 90% of car industry uses halogen bulbs for headlight because the light intensity is twice as high as that of incandescent bulb. First halogen bulbs (H1, H2 and H3) had just one filament and were mainly used for taillight and aditional light. Now we have H4 bulbs for combination of taillight and main beam. Their advantage is that the bulb does not darken during the lifespan of the lamp and the flux is more constant.
New H7 bulb can be used without restrictions in modern complex headlights with up to 45% more light on the road depending of the headlight construction. That anables better visibility and safer traffic. They produce lower glare with 20-30% more light intensity on the road for main beam and taillight.