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Two functions of fluorescent light ballast
2015-10-14 00:18:08
Fluorescent light ballast has two functions, one is when the starter disconnect the moment of fluorescent lamp circuit generating high voltage, breakdown fluorescent lamp mercury vapor circuit, the filament circuit conduction; the second is self induced electromotive force in the ballast blocks alternating current changes, the flowing through the lamp tube current do not generally understood in fluorescent light ballast in fluorescent lamp circuit with function.
The fluorescent lamp is mainly composed of the lamp, fluorescent lamp ballast and starter. The two ends of the lamp tube have a filament, and the tube is filled with argon and micro mercury vapor, which is coated with a fluorescent powder. The working principle of the lamp and incandescent lamp is different, the gas between the two filament in the conduction time mainly emits ultraviolet ray, the fluorescent powder by the ultraviolet radiation to emit visible light. Different types of fluorescent powder, the color is not the same as the color of the gas has a characteristic: only when the voltage at both ends of the tube to reach a certain value of the gas in the lamp tube to maintain a certain size of the current, the required voltage is much lower. Therefore, if the voltage of the 220V is added to the two ends of the tube, it can not be ignited. The ballast and starter can solve the problem of ballast is wound on the iron core coil, inductance. Starter by sealing static in the glass bubble contact piece and a U-shaped moving contact piece composition, glass bulbs filled with neon. Two contact pieces with a certain voltage, neon light, electricity, heating. 
James contact sheet is bonded together in a double metal sheet made of, after being heated, two layers of metal expansion of different, dynamic contact piece with a bit of a stretch, and static contact pieces starter should cease to shine its light, then a bimetallic strip cooling, contact piece shape restoration, two contacts apart again after closing the switch voltage through the filament of the fluorescent lamp and at the two ends of the starter, starter above the heating - contact - cooling - off contact.
In the instant of contact, the current in the ballast L is reduced sharply, which produces a high induction electromotive force. Induction electric potential and power supply voltage superimposed on both ends of the lamp, the lamp is lit. The actual use of the launcher is often a capacitor connected in parallel at both ends of the neon bulb, it can make the two contact pieces in the separation does not produce sparks, so as not to burn the bad contact, but also can reduce the interference to the nearby radio equipment. No capacitor starter can work at home lighting power is AC, its size and direction are constantly changing. Stop stop direct expansion because of the principle of ballast l self inductance electromotive force to stop the flow of current changes, making flowing through the tube current is not caused by too large by the above and below the pictures can know, power supply is switched on, the double metal sheet and the static slice is a certain distance, the distance will produce the glow discharge, the discharge heat make the double metal sheet is heated, U shaped double metal sheet metal inside, then outward expansion, expansion of the double metal piece and the static contact piece, the circuit conduction, discharge, double metal sheet is heated, and the cold start is due to the circuit conduction, two filament heating, Mercury also evaporate into mercury vapor. 
When the bimetal cooling for a while, to restore the original shape, the circuit is cut off; at the same time conducting filament of mercury vapor lamp lit, this double metal sheet and between the static sheet no glow starting voltage, cannot be renewed Hui here know bimetal in open daylight lamp has played a role in the circuit is switched on. If you do not have a double metal film, regardless of the expansion coefficient of large or small, U shaped pieces of heating or U shaped, not and static contact, it will not lead to circuit, will not heat the filament, it will not light the lamp. So we have to use double metal pieces.

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