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TRANSISTORISED IGNITION SYSTEM

 A transistor interrupts a relatively high current carrying circuit. i.e It controls a high current in the collector circuit with a small current in the base circuit. Therefore, a transistor is used to assist the work of a contact breaker. Hence , This system is known as Transistor -assisted ignition system or transistorized ignition system. 

CONSTRUCTION : 

It consists of a Battery , Ignition Switch , Transistor , collector , emitter , ballast resistor , contact breaker , Ignition coil, distributor and spark plugs. The emitter of the transistor is connected to the ignition coil through a ballast resistor. Collector is connected through a battery. 

WORKING : 

The cam is in the distributor is rotated by the engine. It opens and closes the contact breaker points. 




When the contact breaker pints are closed ,

1. A small current flows in the base circuit of the transistor. 

2. A large current flows in the emitter or collector circuit of  the transistor and the primary winding of the ignition coil due to the normal transistor action.

3. A magnetic field is set up in the primary winding of the coil.

When the contact breaker points are opened :

1. The current flow in the base circuit is stopped. 

2. The primary current and the magnetic field in the coil collapse suddenly due to the immediate reverting of the transistor the non- conductive state. '

3. It produces a high voltage in the secondary circuit . 

4. This high voltage is directed to the respective spark plugs through the rotor of  the distributor.

5. This high voltage produces a spark when it is tried to jump the spark plug gap. It ignites air fuel mixture in the cylinder. 

ADVANTAGES :

* It increases the life of contact breaker points.

* It gives higher ignition voltage.

* It gives longer duration of spark.

* It has very accurate control of timing.

* Less maintenance.

DISADVANTAGES :

* Mechanical points are needed as in conventional system.

* It has a tendency to side tracking.

 

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