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The tungsten particles released
close to the filament tend to reduce the amount of evaporation so the filament and thus the lamp
lasts longer. However, the lamp will not last for ever because the filament will eventually break
at its hottest point.
Halogen lamps have a higher colour
temperature because it is possible to run the filament hotter which means an increase in light
output.
Figure 8.3. Operating principle of
halogen lamp.
Features and Benefits
Halogen lamps offer a number of important features and user benefits.
Firstly, longer lamp life as shown
in Figure 8.4.
Halogen lamps last up to five times
longer than standard incandescent lamps. Major benefit: lower lamp replacement costs - replacement
labour cost reduced 50-80%, less frequent lamp changing.
Figure 8.4. Longer lamp
life.
Secondly, there is more light
output. Figure 8.5 shows that the initial light output of a halogen lamp is higher than that of a
standard incandescent lamp. The light output of the halogen lamp decreases only about 5-6% through
life so it has excellent lumen maintenance. The light output of the standard incandescent lamp
fails by about 20% over a shorter life span. The halogen lamp has a higher lamp efficacy by
comparison.
More consistent light output is
also important for many applications such as photography and theatre lighting.
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