Transcript Electrical Installation Practice 2

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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 Vapour
Requires a ballast to limit running current
• External
Starting is achieved buy a auxiliary
• Internal
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 Vapour
• 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 Vapour
Contains xenon as well as some mercury
The colour difference between HPS and LPS is due to
• Higher gas pressure slightly less than 1 atmosphere
• Higher temperature 1100°C
Pressure Broadening
• Addition of mercury
Arc tube is typically made of translucent
sintered aluminium oxide.
Efficacy 100 lm/W
Near the end of their life exhibit a phenomenon known as cycling
Metal Halide
Quartz discharge tube containing
• high-pressure mercury
• Sodium halide
• Scandium halides
Argon is used to aid ignition.