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Tube light | Fluorescent lamp | how it is working? Explanation with wiring diagram

Scheme: Fluorescent lamp

What is Fluorescent lamp?
A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, which produces short-wave ultraviolet light that then causes a phosphor coating on the inside of the lamp to glow.

A fluorescent lamp converts electrical energy into useful light much more efficiently than incandescent lamps. The typical luminous efficacy of fluorescent lighting systems is 50–100 lumens per watt, several times the efficacy of incandescent bulbs with comparable light output.                              (by Wikipedia)

Tube light|Fluorescent lamp wiring diagram:

The Tube Light|Fluorescent lamp Wiring diagram is clearly given below;

Scheme: Fluorescent lamp wiring diagram

               1. Fluorescent lamp 2. Ballast/Choke 3. Starter 4.Frame 5. Lamp holder 6. Capacitor 7.Switch

Names of important elements:
Following are the names of the important components required to do Tube Light | Fluorescent lamp Wiring,

1. Fluorescent lamp:
A fluorescent tube is loaded with a gas containing low-pressure mercury vapor and argon. The pressure inside the lamp is around 0.3% of environmental pressure. The inward surface of the lamp is coated with a fluorescent. This coating is made of shifting mixes of metallic and uncommon earth phosphor salts. The lamp’s anodes are normally made of snaked tungsten and typically alluded to as cathodes due to their prime capacity of discharging electrons.

For this, they are coated with a blend of barium, strontium, and calcium oxides to have a low thermionic emission temperature.

2. Choke:
This is commonly called as `choke´ or ´Ballast`. In a fluorescent lighting system, the ballast regulates the current to the lamps and provides sufficient voltage to start the lamps.

3. Starter:
Starters are commonly known as bi-metallic contacts. The starter is a time-delay switch that opens and close after a second or two. When the switch is ON starter allows current to flow through the filaments at the ends of the tube.

4. Frame:
These are the backbones of Tube light. These hold the lamp, choke, holder and starter.

5. Holder:
Lamp holders, also known as light sockets. Lamp holders are the ones that connect the bulb with supply voltage also provide mechanical support for a lamps.

6. Capacitor:
Mostly in the lamps capacitor is used only for power factor improvement. That's why capacitor is connected between supply voltages as shown in fig.

7. Switch:
Use a simple on-off switch. This type of switch is called SPST (single pole-single throw)and its action is described as ON-OFF. The switch has two positions: closed = on and open = off, but it is called 'single throw' because only one position conducts.

How a Fluorescent lamp works:

Scheme: Fluorescent lamp working

We can now see in detail how tube light works:

  • Let me take you to a little imagination now. Suppose you switch on, 230 volt, 50Hz AC supply is connected between terminals P and N as soon as you switch on.
  • When an AC voltage is applied to a tube light, the voltage passes through the choke, the starter, and the filaments of the tube. 
  • The filaments light up and instantly warm up the tube. The starter is made up of a discharge bulb with two electrodes next to it. When electricity passes through it an electrical arc is created between the two electrodes. This creates light, however the heat from the bulb causes one of the electrodes (a bimetallic strip) to bend, making contact with the other electrode. 
  • This stops the charged particles from creating the electrical arc that created light. However, now that the heat from the light is gone, the bimetallic strip cools and bends away from the electrode, opening the circuit again.
  • At this point, the ballast or choke push back it’s stored energy, which again passes through the filaments and ignites the tube light once again.
  • If the tube does not sufficiently charge up, subsequent kicks are delivered by the choke due to rapid switching of the starter, so that finally the tube strikes.
  • After this the choke only acts like a low impedance current limiter to the tube as long as the light is kept illuminated.

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