OSRAM DULUX F - Manual (Page 83)

Economical long-life light sources with plug-in bases
Compact Fluorescent Lamps OSRAM DULUX ®
Technical Guide
81
5.1.4 Dimming
Reducing the lamp current below the minimum value specified in 5.1.3 can be used to reduce the
luminous flux of the lamp appreciably below its rated value, thereby dimming the lamp. The
dimming range is defined as the lamp current region between the “minimum lamp current
(undimmed)” and the “minimum lamp current” in the table below. Please note the following:
The lamp electrodes must be maintained at emission temperature by a continuous heating
current.
The lamp voltage at lower discharge current is generally higher than the rated value.
The chromaticity coordinate of the light colour may deviate from its rated value.
In the interest of maximising lamp life, the auxiliary heating current must be matched to the lamp
current. If the auxiliary heating current is too low, the lamp electrodes will very quickly be destroyed
by sputtering. A constant heating current that is too high will result in excessive emitter evaporation
which leads to end blackening.
Generally speaking, it is not easy to measure the continuous heating current when the lamp is being
operated on an electronic control gear (BAT) because of two reasons. First, the current is fed to the
electrodes in the lamp via the two lead wires in a split that depends on the design of the control
gear. Second, the lamp current and the auxiliary heating current may differ in phase, wave shape
and frequency. Therefore it is not reasonable to specify the necessary auxiliary heating current as a
function of the lamp current.
The important variable for electrode heating is the electrical heating power P heat fed to the electrode.
As:
2 2 2 2 ,
Heat d Heat d current Heating current Lamp Heat
I I f I I f P P P
or
2
2
2
1 Pin Pin Heat
I I f P