5
3.4 Power factor correction
Mains voltage |
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Circuit | Ind. |
| Cap. | Ind. |
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| Cap. |
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Z ballast (Ω ) | 440 |
| 440 | 400 |
| 400 | 360 |
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Z capacitor (Ω ) |
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Z result (Ω ) | 440 |
| 360 | 400 |
| 400 | 360 |
| 440 |
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Therefore the behaviour of the inductive and capacitive branch of a
Fig. 116. Voltage/current characteristic of an inductive ballast (example).
V ballast (V)
180 |
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| 1 |
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| Z1 | = | 165 | = | 360 |
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160 |
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| Z1 = | 150 | = | 400 |
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140 |
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| 0,375 |
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| 3 |
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| Z1 = | 135 | = | 440 |
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120 |
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100 |
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80 |
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60 |
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40 |
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20 |
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| 100 | 200 | 300 | 400 | 500 | 600 | 700 | 800 | 900 | 1000 |
I ballast (mA)
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
Fig. 117. Tandem circuit with two lamps in series on a common ballast.
‘TL’1
S
‘TL’2
S
123