What is Electric Traction? – Definition, Advantages and Disadvantages

Electric Traction

The action of pulling something over a surface (especially a road or a track) is known as traction. The action of drawing of vehicles by electric power derived from overhead wires, third rail, storage batteries or diesel generators mounted on the vehicles is known as electric traction. In simple words, the traction system which uses electric power for its operation is known as electric traction.

The electric traction system is widely used in electric trains, tramcars, trolley buses and hybrid vehicles, etc.

Advantages of Electric Traction

The major advantages of electric traction system over other types of traction (such as steam traction) are described below −

  • Cleanliness − Electric traction is free from smoke and flue gases, etc. Therefore, it is most suitable type of traction system to be used for underground and tubular railways.

  • Less starting time − Electric locomotives can be stating without any loss of time.

  • Less maintenance cost & time − The maintenance cost of an electric traction system is about half of that of steam traction system and also the time required for maintenance is quite low.

  • High starting torque − The motor used in electric traction is DC series motor or AC series motor which has a very high starting torque. Hence, the electric locomotives has very high acceleration about 1.5 to 2.5 kmphps.

  • High traffic handling capacity − As the electric locomotives have high acceleration which makes the traffic handling capacity almost double of that of the steam locomotive.

  • Require lesser terminal space − As the electric traction has high traffic handling capacity. Therefore, it needs lesser terminal space because quicker disposal of passengers to destination is there and hence gathering is reduced.

  • Regenerative braking is possible − In case of electric traction system regenerative braking can be applied which feeds back about 80% of electrical energy to the supply. Also, due the presence of electric braking, there is less requirement of mechanical braking. Thus, maintenance cost of brake shoes, wheel types and rails get reduced on account of less wear and tear.

  • Center of gravity − Height of electric locomotive is quite less as compared to steam locomotive which results in lowering of center of gravity. This makes the electric locomotive more suitable for taking curvy turns at higher speeds safely.

  • Saving in high grade coal − The use of electric locomotive saves high grade coal which is quite deficient in India. Electrical energy required for running electric locomotives is taken either from hydro-electric power station or thermal power station which uses low grade coal for electricity generation.

  • Absence of unbalance Forces − Due to absence of unbalanced forces produced by the reciprocating masses, the coefficient of adhesion is more for electric traction. This reduces the weight to power ratio of locomotive.

  • Electric traction has high power-to-weight to ratio.

  • The electrification of railway encourages rural electrification.

Disadvantages of Electric Traction

In spite of the fact that the electric traction has so many advantages, it suffers from many disadvantages which are given below −

  • Electric traction has high capital cost due to overhead equipment, so electric traction becomes uneconomical unless heavy traffic is to be handled.

  • In electric traction, a power failure for few minutes causes distortion in traffic.

  • Electric traction can be used only at the places which are electrified.

  • Electric traction is tied to electric routes.

  • Power lines for electric traction causes disturbance in neighboring communication lines.

  • In electric traction system, provision of negative booster is necessary, otherwise it results in corrosion of underground pipes.