Indoor Furnishings User Manual

Features of electronic ballasts
As stated,‘TL’5 lamps are exclusively designed for HF-operation,
resulting in higher lamp efficacies and lower ballast losses,
furtheron,compared with conventional gear, an electronic ballast
offers the following benefits and features:
• Low energy consumption
• No flickering lamps
• No flicker when switching on the light
• Automatic stop-circuit is activitated within five seconds in
case of lamp failure (safety stop);once the lamp has been
replaced,the ballast resets automatically
1.2 Working principle of the ‘TL’5 lamp
A ‘TL’5 lamp is a low-pressure mercury lamp (just like ’TL’D).
The tubular fluorescent lamp works on the low-pressure mercury
discharge principle. (Fig. 1.1)
The discharge tube has an electrode sealed into each end and is
filled with an inert gas and a little mercury, the latter being present
in both liquid and vapour states.
The inner wall of the tube is coated with a mixture of fluorescent
powders.These convert the ultraviolet radiation of the mercury
discharge into visible radiation (light).
Many different fluorescent powders or ‘phosphors’ are available for
this purpose, which by judicious mixing can produce light of almost
any desired colour temperature and colour rendering characteristic
with a high efficacy compared with other light sources producing
white light.
Just like all low-pressure mercury lamps ‘TL’5 lamps need a current
limiter.The ‘TL’5 lamp especially was designed to operate on an
electronic ballast.
Because the higher efficacy with ‘TL’5 only is attained with high
frequency operation,50 Hz operation is not recommended or
supported.
1.2.1 Optimum operation of ‘TL’5 lamps with cold
chamber (cold-spot technology)
The luminous flux of a low-pressure mercury vapour lamp is deter-
mined by the mercury pressure which on its turn is dependent on
the temperature of the coldest spot in the lamp.
The maximum light output of the lamp is reached at a cold spot
temperature of approx.45 °C. In case of the ‘TL’5 lamp this cold
spot is situated behind the electrode at the stamp side:the so-cal-
led cold chamber. (See Figure 1.2)
The ‘TL’5 lamp was designed to reach its maximum flux at 35 °C
ambient temperature in draught-free air when operated on gear
without additional heating of the electrodes.Such a ballast is called
a cut-off ballast.
35 °C is the common ambient temperature within luminaires.
Any deviation from these nominal conditions for operation will
influence the light output of a ‘TL’5 lamp.
This can happen:
– If the design of the luminaire allows an ambient temperature
near the lamp(s) deviating from 35 °C
– If the nominal specifications of the gear include a lamp current
deviating from the nominal value and/or include heating of the
electrodes during operation.The additional power dissipation
will heat the spot behind the electrodes and so will result in a
shift of the curve of the output of the luminous flux:the top will
be reached at lower ambient temperatures,for that reason the
use of cut-off ballasts is recommended with ‘TL’5 lamps.
For further details about deviation from the normal operation
conditions see 2.5.
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2000-11-07
Figure 1.1: Working principle of a tubular fluorescent lamp
Figure 1.2: Lamp end with cold chamber (lamp stamp end)
Visible radiation
Fluorescent powder Mercury atom Electrons Electrode
Ultraviolet radiation
Cold spot (within the lamp)
Stamp