Post on 21-Mar-2016
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ContentContent• Types of high intensity discharge lights• Colour rendering of high intensity discharge
lights• Operating principles of high intensity
discharge lights• Control equipment associated with high
intensity discharge lights• Efficacy of high intensity discharge lights• Common faults in discharge lights discharge
lamps.
High Intensity Discharge Lamps
•Mercury Vapour•High Pressure Sodium Vapour•Metal Halide
Mercury VapourRequires a ballast to limit running current•External•Internal Starting is achieved buy a auxiliary
electrode and resistor in the lamp
External Ballasted HPMV
Auxiliary electrode
Resistor
Internal Ballasted HPMV
• High-pressure mercury tube in series with a tungsten filament• Runs on mains voltage without additional gear• Combines a continuous spectrum from the incandescent
source and high pressure mercury source
High Pressure Sodium High Pressure Sodium VapourVapour• Requires a Ballast for control of running current• Ignitor to start the arc in the lamp
Some smaller lamps may have an Ignitor incorporated in the lamp
High Pressure Sodium High Pressure Sodium VapourVapour
Contains xenon as well as some mercury
The colour difference between HPS and LPS is due to
• Higher gas pressure• Higher temperature• Addition of mercury
Efficacy 100 lm/W
Arc tube is typically made of translucent sintered aluminium oxide.
Pressure Broadening1100°C slightly less than 1 atmosphere
Near the end of their life exhibit a phenomenon known as cycling
Metal HalideMetal Halide
Quartz discharge tube containing•high-pressure mercury•Sodium halide•Scandium halidesArgon is used to aid ignition.