OSRAM DULUX F - Manual (Page 54)

Economical long-life light sources with plug-in bases
Compact Fluorescent Lamps OSRAM DULUX ®
Technical Guide
52
3.3.1 Compact fluorescent lamps in emergency lighting
Requirements for emergency lighting
Emergency lighting applications often supply a significantly reduced discharge current with respect
to the specified discharge current without auxiliary coil heating. This is done to extend the opera-
tional time when the system is operated on batteries.
From the description of dimmed fluorescent lamp operation it is well known that if a fluorescent
lamp is operated below 80% of the standardized test current auxiliary coil heating is necessary in
order to prevent an increase of the cathode fall voltage, which will lead to sputtering on the coil and
early lamp failure.
If a lamp is operated in the so called dimmed zone of discharge current below 80% of the test cur-
rent without any coil heating, lamp life will be reduced by a higher factor the lower the discharge
current to test current ratio gets. The diagram below shows a rough estimate of operational time
which can be expected.
If a lamp is operated in the dimmed zone without auxiliary heating, the coil will be damaged as ex-
plained above. If the operation in the dimmed zone is only for a limited time interval and the lamp is
then again operated according to the specification, the damage can be partly corrected. Unfortu-
nately the coil cannot recover completely from the damage. The more often dimmed operation with-
out coil heating happens the more lamp life is further reduced. It is very difficult to estimate this
lamp life reduction because it strongly depends on the time schedule of normal operation (i.e. ac-
cording to the specification) and dimmed operation without coil heat.
0%
20%
40%
60%
80%
100%
0% 20% 40% 60% 80% 100% 120% 140%
la
mp
l
if
e
[
%
r
a
te
d
]
discharge current [% rated]
Estimated lamp life reduction with reduced discharge current