Good to know

Lamps and reflectors

Base down means temperature in base controlled. The life of the lamp is reduced since gravity has a negative impact on the electrodes. Usually applicable for uplights. Lamplife timetest carried out like this freeburning. Horizontal is the preferred burning position for long life, but it is not as good for reflector beam control in lightfittings. Double-ended lamps have longer life. Especially powered by electronics.

Base up means temperature in base increased. The life of the lamp is reduced since gravity has a negative impact on the electrodes. Usually applicable for downlights. Pinch temperature increased.

Electronics in fixtures

Temperatures over Tc shorten gear lifetime. For instance +10° C reduces the lifespan of most semi-conductors by 50%. Temperatures below Tc extend lifetime. For instance -10° C doubles the lifetime of most semi-conductors.

Ta = ambient max gear temp according to design.
Tc = critical component temperature according to design.

Lamplife definitions

Average life. 50% of lamps confirmed to last according to the statements from suppliers in free-burning base down application. Definition set when either light flow, color rendering and mortality reach the level 50% of defined performance.
Economical life. 70% of lamps confirmed to last according to the statements from suppliers in free-burning base down application. Definition set when either light flow, color rendering and mortality reach the level 70% of defined performance.
Service life. 80% of lamps confirmed to last according to the statements from suppliers in free-burning base down application. Definition set when either light flow, color rendering and mortality reach the level 80% of defined performance

Spreading angle from reflectors

Shown angles are measured in darkroom and correspond to the international Elumdat standard requiring 50% of light flow to be within the indicated angle. The standard does not specify where the remaining 50 % of light flow outside the stated angle must be distributed, making it difficult to compare the results with other suppliers. Observe straylight not defined.

Electronic prognostics/ Reliability “bathtub” curve

Bathtub Curve Showing Failure Rate with Time, along with Remaining Useful Life (RUL) Period. Failure probability for a device typically follows a bathtub curve, with three distinct regions;

1) Infant Mortality (Burn-In) Region. Initial higher
probability of failures, related to manufacturing
defects.
2) Useful Life Period. Minimum, almost constant,
failure rate mostly by temperature, vibration etc.
3) Wearout (End-of-Life) Region. Due to wearout or
fatigue mechanisms, probability of failure increases.

Default Ratio; Electronics general ”Bathtub” curve scenario:

A) Extreme. Burn-in period provoked by NL to ”achieve”
failures at factory to limit field problems.

B) Approx 3-5 pcs per 1 000 could occur during this period

C) Temperature related running lifetime. Tc=+10° C
above gear Tc means 50% lifetime decrease
expectancy.  Tc=-10° C below gear Tc means
200% lifetime increase expectancy. Remarks NL
has fixtures already built 1993-1995 still running
in shopwindows.

D) Time death by aging.