Introduction Electric traction means a locomotion in which the driving force is obtained from electric motors. Electric traction will continue to play a dominant role in the Railway since it is an environmentally clean technology compared to diesel traction and also its running cost is low. There are many advantages of electric traction over other forms of locomotion.

Ideal Traction System Maximum tractive effort should be exerted at starting Equipment should be capable of overloads for short periods The wear caused on the track should be minimum Braking should be possible without excessive wear on the brush

Advantages & Disadvantages of Electric Traction Cheapness, Acceleration & Braking, Cleanliness, Maintenance Cost, Starting time, High starting time, Braking, Saving in high-grade coal, Better co-efficient of adhesion Disadvantages High initial expenditure Failure of supply is a problem Electrically operated vehicles have to move only on electrified track For braking & control, additional equipments required

System Of Track Electrification D.C. Systems A.C. Systems (a) Three phase A.C. system (b) Single phase standard frequency system (c) Single phase low frequency system (d) Single phase to three phase system [Kondo system]

Advantages & Disadvantages of 25 kV A.C. System Over D.C. System Light overhead catenary Saving in sub-stations More flexibility Lesser equipment used & easy to maintain Starting efficiency Cheap as far as cost for fixed installation Disadvantages Single-phase A.C. system imposes Unbalancing effect Produces interference with telecommunication lines

Railway Service Categories Main line service City service Suburban service

Block Diagram Of an A.C. Locomotive

Review Of Existing Electric Traction In INDIA Before independence in our country electric trains are working in western region near Bombay & in southern region Madras. The Tram cars, however were also working in some cities. All these system operated & still operating on D.C. supply of 1500 V & 600 V for trains & trams respectively.

Auxiliary Equipment Overhead conductors for track electrification Pantograph Transformer or Auto-transformer Rectifier unit Driving axle & gear arrangements Train lighting Multiple control

Braking Characteristics If any electric motor is to be stopped, electric supply to it is disconnected. In this way, the motor shall take long time to stop, as the motor shall continue to rotate due to inertia. Some braking system must be used so that it stops within the pre-determined short time. A good braking system must posses the following features It should be fast and reliable. The braking force must be capable of being controlled Kinetic energy of the rotating parts of the motor and its driven machine must be suitably dissipated & suitable means must be provided.

Advantages & Disadvantages of Electric Braking It is quite fast It is quite cheap as far as maintenance part Higher speed can be maintained Heat produced during braking is not harmful It is free from fires and is smoother Disadvantages It can stop the motor but it cannot hold it stationary. It cannot be applied to all motors Its initial cost is very high.

Types Of Electric Braking Plugging Braking Rheostatic Braking Regenerative Braking

Conclusion India with its large railway network and the growth of large metropolitan centers is building up a large market for railway transport equipment. Clean technologies due to environmental considerations. Energy conservation to minimise wastage of power. Faster/reliable railway transportation. The success of space, defence and atomic energy can be replicated by the Railways also.

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