Monday, October 14, 2013

Working principle of Choke; Specifications of Choke

Choke is very important of Tube light. Usually tube light doesn't work without choke.


Normal operating voltage of tube light is about 110 but naturally available voltage is 240 V in India hence the choke comes into picture which gives 110 V output.

But for initiating the light (to ionize the gas in the tube) the system, system requires 800 - 1000 V to provide this starter has been used, which block the current flowing from the choke to light hence the voltage will build up across the load. once the maximum voltage reached which starter can withstand, the starter closes the circuit and the build up voltage applied across tube light.

Choke is actually an Inductor As we know inductor opposes the rate of change of current here we are making current I which is intially drawn to zero with the help of bimetallic contacts present in starter

According to formulae E=L*di/dt here L is constant and di is equal to I-0 and dt is time taken for I to become zero Accordingly high voltage is induced and this voltage is sufficient to drive the electrons from one electrode to another electrode inspite of medium present between electrodes.

Once conduction starts there after choke just provide voltage which is sufficient for conduction i.e. 110V.

Choke is shown in Tube light circuit as:-

Choke functions in Tube light

 Thus Choke performs two functions:-
 1. Provide high voltage during starting for ionization of Gas
 2. Provide low voltage for continuous working of tube light.

There are two types of chokes available in the Market:- 

1. Copper choke.
2. Electronic choke.

A copper choke usually has following specifications:-

 For single tube light  current taken by choke is 0.39 A and Power factor of 0.5 only with Delta T of 70 and an Electronic choke Power factor ranges between 0.8 to 0.9.

 Electronic chokes are thus now most widely used as PF is very high so current drawn will be low. Also losses in copper choke are high then electronic choke also there is no light flickering occurs while starting electronic choke tube in comparison to Copper choke.