Discharge lamps

From Electrical Installation Guide

See also "Lighting circuits" for more details

The power in watts indicated on the tube of a discharge lamp does not include the power dissipated in the ballast.

Figure A8 gives the current taken by a complete unit, including all associated ancillary equipment.

These lamps depend on the luminous electrical discharge through a gas or vapour of a metallic compound, which is contained in a hermetically-sealed transparent envelope at a pre-determined pressure. These lamps have a long start-up time, during which the current Ia is greater than the nominal current In. Power and current demands are given for different types of lamp (typical average values which may differ slightly from one manufacturer to another).

Fig. A8 – Current demands of discharge lamps
Type of lamp (W) Power demand (W) at Current In (A) Starting Luminous efficiency (lumens per watt) Average timelife of lamp (h) Utilization
PF not corrected PF corrected x In Period (mins)
230 V 400 V 230 V 400 V 230 V 400 V
High-pressure sodium vapour lamps
50 60 0.76 0.3 1.4 to 1.6 4 to 6 80 to 120 9000
  • Lighting of large halls
  • Outdoor spaces
  • Public lighting
70 80 1 0.45
100 115 1.2 0.65
150 168 1.8 0.85
250 274 3 1.4
400 431 4.4 2.2
1000 1055 10.45 4.9
Low-pressure sodium vapour lamps
26 34.5 0.45 0.17 1.1 to 1.3 7 to 15 100 to 200 8000 to 12000
  • Lighting of motorways
  • Security lighting, railway stations platforms
  • Platform, storage areas
36 46.5 0.22
66 80.5 0.39
91 105.5 0.49
131 154 0.69
Mercury vapour + metal halide (also called metal-iodide)
70 80.5 1 0.40 1.7 3 to 5 70 to 90 6000
  • Lighting of very large areas by projectors (for example: sports, stadiums, etc.)
150 172 1.80 0.88
250 276 2.10 1.35
400 425 3.40 2.15
1000 1046 8.25 5.30
2000 2092 2052 16.50 8.60 10.50 6 2000
Mercury vapour + fluorescent substance (fluorescent bulb)
50 57 0.6 0.30 1.7 to 2 3 to 6 40 to 60 8000 to 12000
  • Workshops with very high ceilings (halls, hangars)
  • Outdoor lighting
  • Low light output [a]
80 90 0.8 0.45
125 141 1.15 0.70
250 268 2.15 1.35
400 421 3.25 2.15
700 731 5.4 3.85
1000 1046 8.25 5.30
2000 2140 2080 15 11 6.1
  • Note : these lamps are sensitive to voltage dips. They extinguish if the voltage falls to less than 50% of their nominal voltage, and will not re-ignite before cooling for approximately 4 minutes.
  • Note: Sodium vapour low-pressure lamps have a light-output efficiency which is superior to that of all other sources. However, use of these lamps is restricted by the fact that the yellow-orange colour emitted makes colour recognition practically impossible.
  1. ^ Replaced by sodium vapour lamps.
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