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).
|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||
|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||
|Mercury vapour + metal halide (also called metal-iodide)|
|70||80.5||1||0.40||1.7||3 to 5||70 to 90||6000||
|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||
- Replaced by sodium vapour lamps.
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.