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Fig. 116. Voltage/current characteristic
of an inductive ballast (example).
Fig. 117. Tandem circuit with two lamps
in series on a common ballast.
5
3.4 Power factor correction
Mains voltage
90 %
Circuit
Ind.
Z ballast (Ω)
440
Z capacitor (Ω)
Z result (Ω)
440
Therefore the behaviour of the inductive and capacitive branch of a
duo-circuit is different at mains voltage deviations and deviations of the
ambient temperature.This can be seen rather well in a duo-luminaire.
V
(V)
ballast
3
3 5
Series connection of lamps
Under certain conditions it is possible to operate two lamps in series
on a common ballast (see Fig. 117).A prerequisite for such operation
is that the sum of the operating voltages of the lamps is not higher
than approximately 60 per cent of the supply voltage.This means that
two lamps, each with an arc voltage of no more than 65 volt, can be
connected in series via a common ballast to the 220/240 V mains.This
restricts the maximum lamp length to 600 mm (2 ft), or the lamp
power to 18/20 W (26 or 38 mm diameter lamps only).
The series circuit can be compensated in the normal way by using a
parallel or series capacitor.
0
123
100 %
Cap.
Ind.
Cap.
Ind.
440
400
400
360
800
800
360
400
400
360
1
Z
= 165 = 360 Ω
____
1
0,458
2
Z
= 150 = 400 Ω
____
1
0,375
Z
= 135 = 440 Ω
____
1
0,307
'TL'1
S
'TL'2
S
110 %
Cap.
360
800
440
I
(mA)
ballast
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