 High Pressure Sodium
High pressure sodium bulbs, usually referred to as SON lamps, give a golden white light and have a long life. They are suitable for use in industrial lighting, warehousing, streetlights and floodlights. Care must be taken in selection if colour discrimination is important.
Construction
Glassware
- Outer jacket in choice of tubular or elliptical form
- Tubular clear glass envelope
- Elliptical envelope is internally coated with titanium dioxide to fully diffuse the light
- Discharge tube is sintered aluminium oxide
- Geometry varies according to lamp type
Cap Type -
Single ended E27 (up to 70w), Rx7s 24 (150w and over)
Double ended Rx7s. (70w), Rx7s 24 (150w)
Gas Filling - Space between the outer jacket and discharge tube is evacuated and gettered to produce a very high vacuum. The arc tube is filled with sodium, mercury and xenon being added.
Electrodes - Heavy tungsten cathodes are fixed into the tube ends using a ceramic thermoset paste.
Starting and Operation
Starting Method - An igniter initiates a discharge in the xenon gas. This generates heat which vaporises the sodium / mercury amalgam and formulates a sodium arc.
Operation - The xenon gas has good insulating properties and this helps the arc tube to warm up quickly.
The pressure rises to about one third of an atmosphere with stability being achieved in 6-8 minutes.
Restrike - less than 1 minute
Operating Position -
Single ended - Universal
Double Ended - Horizontal ±45o
-40oC minimum starting temperature
Physical Characteristics
Colour - Warm White
Correlated Colour Temperature:
| SON Standard |
2000oK |
| SON Deluxe |
2200oK |
| SON Super |
2000oK |
| Colour Rendering Index (ra) / Group |
| SON Standard |
23/4 |
| SON Deluxe |
60/2B |
| SON Super |
25/4 |
Chromaticity Co-ordinates-
| SON Standard |
x=0.530 y=0.415 |
| SON Deluxe |
x=0.506 y=0.412 |
| SON Super |
x=0.530 y=0.422 |
| Efficacy - UP to 139lm/w eg |
| SON DL 400 |
= 90 lm/w |
| SON S 400 |
= 129 lm/w |
Application
High pressure sodium lamps produce a warm 'golden' white light. An ideal alternative to SOX lamps for street lighting where a warmer, superior light quality with the ability to distinguish colours is required. Ideal also for floodlighting and industrial interior lighting.
The choice of clear or diffused envelopes allows for a wide variety of floodlighting possibilities.
SON Deluxe, having improved colour rendering can be used in industrial applications requiring colour distinction and commercial applications.
Source : Crompton Lamps |
