Indoor Furnishings User Manual

2000-11-07
5
2.1 Introduction
In this chapter,recommendations and data are given to enable an
optimal luminaire design.
2.2 IEC Recommendations
The general recommendations for luminaire design by IEC are also
applicable to ‘TL’5 luminaires.Lamp-related data can be found in
IEC 61195.
2.3 Miniaturization
The ‘TL’5 lamp with a diameter of about 16 mm is 40% thinner
than the existing ‘TL’D lamp which has a diameter of 26 mm.The
new lamp fits better in existing ceiling system modules as it is 50 mm
shorter.The thin lamp also gives luminaire designers much freedom
in redesign of their products, making it easy to build lighting systems
which meet customers’ needs,offering reduced dimensions,weight
and height.
‘TL’5 lighting systems are very suited for general lighting
purposes,like in offices,industry and shops.
Luminaires for ‘TL’5 lamps can be made almost half as narrow as
existing ‘TL’D luminaires.The small dimensions of the system allow
luminaire designers to apply the ‘TL’5 system also in less traditional
lighting systems like miniaturized suspended lighting elements and
for integration into shop furniture elements.
2.4 Operating temperatures ‘TL’5 lamps
2.4.1 Lamp temperatures
Test requirements
The data on the ‘TL’5 lamps are based on free burning conditions
on a reference circuitry and the lamp should be tested that way
also,unless stated otherwise.
2.4.2 Maximum temperatures of lamp parts
Luminaires for ‘TL’5 lamps must satisfy the general requirements for
luminaires as specified by the IEC Publication 60598 and,if applica-
ble, comply with the requirements of local standards.The maximum
allowed temperature of the lamp cap is 120 °C,as given in IEC
Publication 61195 - Double-capped fluorescent lamps - Safety speci-
fications.
2.4.3 Measuring the lamp cap for optimum lamp
conditions
‘TL’5 lamps will reach maximum light output at 35 °C ambient
temperature in draught-free air.For a given lamp power and
ambient temperature the circumstances within a luminaire are
chiefly determined by:
– the dimensions and type of material of the luminaire
– the position of the ballast
– the degree of ventilation (open,half-open, closed luminaire).
A direct relation exists between the light output of the lamp and
the temperature of the mercury in the cold spot: at a temperature
of the mercury of 45 °C a maximum in light output will be reached.
As the cold spot is situated near the metal cap,at stamp side,the
temperature of this cap is a good indication of the pressure of the
mercury (see Figure 2.1).
So for checking the lamp condition the cap temperature (T
cap
) can
be used:if T
cap
≈ 45 °C in stable condition,the lamp has maximum
light output.
2.5 Effects of luminaire design on the lamp
performance
2.5.1 Cold spot
Special attention is needed for the situation when a “cold spot” is
created on the glass tube (due to local air flow, physical contact
with metal parts of the luminaire, etc.) This might make the cold
chamber, near the lamp cap,obsolete and the thermal behaviour in
that case might deviate from the one expected.This phenomenon
can be used at very high ambient temperatures:creating a cold spot
to bring the lamp in optimum condition.
2.5.2 Air-handling luminaires
With an ambient temperature within the luminaire of 35 °C in
draught-free air,the cold spot will be at about 45 °C and the lamp
will be at maximum light output.In that condition an insulating air
layer around the lamp is making the 10 °C difference between the
ambient air temperature and the lamp cap temperature.
If the air is moving around the lamp the mentioned difference is
smaller, resulting in lamp fluxes lower than maximum.One solution
is to cover the cold spot (lamp cap at lamp stamp end) with an
insulating material to reach optimum light output at lower ambient
temperatures.
2. Luminaire design
Figure 2.1
35 4545
100
50
Lamp cap temperature in °C
Relative luminous flux in %
55 6525