Philips Electromagnetic Lamp Main starter function, Starter types, 113, Glow-switch starters

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1.7 Watt losses

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.

STARTERS	2
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2	1	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.

2 2 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:Vpeak = 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

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