Exterior Lighting 2012/2013 - Fergin AB

The luminaire efficency ( LB ) is always smaller
than the optical output ratio because in the case
of the light output ratio, the lamps burn at varying
ambient temperatures, e.g. in enclosed light fittings.
The utilization factor( B ) is calculated from the
light output of the light fittings and local conditions,
e.g. indoors reflections from the walls and ceiling
are to be taken into account. The result is the room
utilization factor ( R).
The room utilization factor is
to be replaced by other factors in case of outdoor
illumination.
The maintenance factor (V) takes into account
the ageing process and dirt build-up of the luminaire
during the period for which a lamp is in place.
Therefore in planning, the reduction factor (V) has
to be considered. It is usually assumed as 0.8.
The main photometric units
The luminous efficacy states how many lumen
of luminous flux a lamp emits per watt of electrical
power. This is a measure of a lamp's economic
efficiency. Incandescent lamps (A) have a luminous
efficiency of only 10–20 Lm/W, fluorescent lamps
(TC-L) 60–90 Lm/W, high pressure lamps (HME,
HIT, HST) between 30–130 Lm/W.
The luminous colour states the effect of a light
source on the colour appearance, created by the
light of a lamp. It is defined with the nearest "colour
temperature". This is the temperature of a reference
standard light fitting at which a balanced luminous
colour is emitted. The three terms "warm white"
(ww), "neutral white" (nw) and "daylight white" (tw)
are used to define the luminous colour.
Size and symbol Designation and correlation Unit and abbreviation
Luminous flux Luminous intensity Lumen [Lm]
Luminous intensity I
Illuminance E
Light density L
Luminous efficacy Lm/W
Half beam angle
Luminousflux
= Candela [cd]
solid angel
Luminous flux
size of area A
= Lux [Lx]
Luminous intensity l
=
visible size of area A
The light output ratio ( ) is a further important
characteristic for the assessment of a light fitting. The
optical light output ratio is the ratio of the luminous
flux being emitted by a lighting unit ( Leu)
to the sum
of the luminous flux ( ), create by all of the lamps
contained in the lighting unit, i.e.
cd cd
2 2 cm m
Luminous flux
= Lumen per Watt [Lm/W]
electrical power N
Imax.
angle at
2
Degrees [°]
Planning aids 367
Planning aids