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What is stroboscopic effect ?


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What do you mean by stroboscopic effect? How is this effect eliminated in fluorescent tube lighting?

All gas discharge lamps operated on a 50 Hz alternating current supply are really flickering off and on 100 times per second. In normal conditions, the human eye does not notice the fact. But when a moving object like rotating parts of machinery is followed, at the certain speed it may appear to be stationary or moving in series of jerks or rotating slowly than its actual speed. This effect of producing an illusion of reality is known as the stroboscopic effect and this is obviously a possible source of danger in factories, machine shops etc.

In fluorescent tube lighting the stroboscopic effect can be eliminated either by using a three lamp unit in which each lamp is connected to a separate phase of a 3 phase, 4 wire supply or by using a two-lamp unit in single phase supply each having its own choke but there is only one condenser connected in series with one of the lamps.

Why is the power factor of tube circuit low and what is the value of the power factor?

Due to the presence of inductive choke the power factor of the tube lamp is about 0.50.

What is the starting and running current of the fluorescent tube ?

0.55 A and 0.37 A for 20 W, 0.65 A and 0.43 A for 40W, 1.00 A and 0.67 A for 65 W & 1.3 A and 0.87 A for 80 W respectively.

What are the available sizes of fluorescent tubes ?

38 cm (15”) for 14 watts, 46 cm (18”) for 15 W, 61 cm (2”) for 20 W, 100 cm (3’- 37/8 “) for 25 W, 122 cm (4’) for 40 W,125 cm (5’)for 65 W and 125 cm (5’) for 80 W.


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