OSRAM DULUX F - Manual (Page 68)

Economical long-life light sources with plug-in bases
Compact Fluorescent Lamps OSRAM DULUX ®
Technical Guide
66
4.6.6 Operation at high temperatures
On conventional linear fluorescent lamps, the cold spot is normally in the centre of the lamp.
Additionally the luminaire will generally have a large radiating surface which will ensure moderate
tube wall temperatures and high efficiency. In contrast to linear fluorescent lamps, compact
fluorescent lamps are much shorter despite having high lamp wattages. Therefore there is a
tendency to make luminaires as small as possible. Often the thermal characteristics are ignored.
In particularly small enclosed luminaire systems the temperatures at the points on normal OSRAM
DULUX
® lamps that have a major influence on luminous flux are so high that luminous flux and
therefore the efficiency of the luminaire are reduced appreciably.
Since in such cases the lamps are no longer operated at their optimum, there are also changes in
the electrical values of the lamp (reduced lamp power) at high ambient temperatures, which in turn
will impair the control gear and shorten the life of the lamp. Therefore it is important to take into
account the maximum temperatures permitted on the lamp (see 4.8).
At high ambient temperatures, where OSRAM DULUX ® Cold Spot lamps cannot be operated at their
optimum (reduced luminous flux), it is advisable to use OSRAM DULUX ® CONSTANT lamps to
achieve maximum luminous flux. Since they achieve their optimum mercury vapour pressure over a
wide range of lamp ambient temperature, CONSTANT lamps operate at their optimum efficiency
under the same conditions in narrow luminaires and therefore achieve a higher lamp power.
All the electrical and photometric values (lamp current, lamp voltage and luminous flux) relate to the
higher lamp output. In narrow luminaires equipped with OSRAM DULUX
® CONSTANT lamps, there
is therefore more heat released than it is the case with Cold Spot OSRAM DULUX ® lamps. This
leads to an increase in temperature at the IEC measuring point of the lamp and the Tc point of the
electronic control gear and must be taken into consideration when designing the luminaires, or
when replacing a Cold Spot lamp by a CONSTANT lamp in an existing narrow fitting. (see
measuring points , chapter 4.8.
For more information related to the maximum permitted temperature at the IEC measuring point,
see chapter 4.8.
4.6.7 Operation at low temperatures
The following points must be taken into account when operating OSRAM DULUX ® lamps on
magnetic ballasts or ECGs at low temperatures:
1. The lamp must be capable of starting at the required temperature.
2. After ignition, the tube wall must warm up sufficiently for the lamp to operate
within its optimum range
The low ambient temperatures at which OSRAM DULUX ® will ignite reliably in conjunction with
magnetic ballasts are shown in 4.2. If operated with suitable electronic control gear, OSRAM
DULUX
® lamps with four-pin bases can ignite at even lower temperatures.
In low-temperature applications, the lamps should be used only in enclosed luminaires. It is
important for the luminaire to be of such volume, that the lamp(s) can warm up rapidly so that
ambient temperatures at which the lamps will operate efficiently are reached within a short time
(especially using CONSTANT lamps, which need a longer time to reach the optimal temperature and
light output – see 4.3). If there are considerable fluctuations in temperature, the luminous
flux/temperature graphs for the different operating positions should be studied in order to achieve a
suitable compromise between lamp and luminaire efficiency.
Operation at low ambient temperatures should be taken into consideration when designing the light
fitting, especially for CONSTANT lamps. This is to improve the run-up behaviour and to enable the
lamps to reach an optimal and stable luminous flux level.