Conventional high-pressure sodium lamps offer a very high luminous output but inferior colour rendition. Their small size and long lamp life make them highly suitable for highway and tunnel lighting systems. High-pressure sodium lamps are operated with ballasts and igniters.


Conventional types


Advantages

  • Very good luminous output (70-130 lm/W)
  • Long lamp life (9,000-10,000 h)
  • Small size


Disadvantages

  • Poor color rendition (Ra = 20)
  • Long starting and restriking times (up to 10 min.)


New types


More modern types of high-pressure sodium lamp are also suitable for interior lighting systems. Although luminous output is lower, colour rendition is good to very good and restriking time is short.


Advantages

  • Good luminous output (40-50 lm/W)
  • Good to very good color rendition (Ra = 60-80)
  • Interior climate similar to incandescent lamps (ww)
  • Fast hot restrike
  • Small size


Disadvantages

  • Ballast, igniter and stabilising gear required