Filter
Top Products
As in some applications the power consumption is of prime importance,
there are low-loss ballasts for the major lamp types ‘TL’D 18, 36 and
58 W ( BTA**L31LW).The 18 and 36 W LW ballasts are bigger than the
standard types, resulting in lower ballast temperatures and 25 to
30 per cent less ballast watt losses. Due to practical restrictions the
BTA 58L31LW type could not be made bigger.The 15 per cent lower
ballast losses are the result of a better iron lamination quality,while
the ballast temperatures are only slightly lower than those of the
standard types.
Main starter function
Fluorescent lamps do not ignite at mains voltage.To ignite the lamps, a
starter is applied to preheat the lamp electrodes and to give a peak
voltage high enough to initiate the discharge.
So in fact there is only one basic function for a starter: to deliver the
ignition voltage to start the discharge in a fluorescent lamp in a proper
way.After ignition the starter has to stop producing ignition peaks.This
can be obtained by sensing the lamp voltage or lamp current and/or
by a timer function.
Starter types
There are two types of fluorescent lamp starters:
1 Glow-switch starters
The glow-switch starter consists of one or two bimetallic electrodes
enclosed in a glass container filled with noble gas.The starter is
connected parallel across the lamp in such a way that the preheat
current can run through the lamp electrodes when the starter is closed
(Fig. 106).At the moment of switching on the mains voltage, the total
mains voltage is across the open glow-switch starter.This results in a
glow discharge starting between the bimetallic electrodes of the
starter.The glow discharge causes a temperature increase in these
bimetallic electrodes,resulting in the closure of the electrodes of the
starter.During this closure the lamp electrodes are preheated by the
short-circuit current of the ballast.After closure the temperature of
the starter electrodes decreases and the starter re-opens.At the
moment of re-opening, the current through the ballast is interrupted,
causing a peak voltage over the lamp electrodes high enough for lamp
ignition.This peak voltage depends on the inductance of the choke,
the level of the short- circuit current and the speed of the opening of
the glow-switch electrodes. In formula:
Peak voltage:V
peak
= L dI/dt
The minimum specified peak voltage depends on the type and is between
800 and 900 V.
If the lamp electrodes are not yet hot enough or the peak voltage is
not high enough, the glow-switch starter will resume the whole
21
52
5
STARTERS
22
113
1.7 Watt losses