ELECTRIC TRACTION                     

ELECTRIC TRACTION

The process of moving any vehicle is called traction. If electric energy is used in this process is called electric traction.

 Electric traction system: - The system which uses electrical power for traction system i.e. for railways, trams, trolleys, etc. is called electrical traction

DC Traction

DC traction units use direct current drawn from conductor rail or an overhead line

The most popular line voltages for overhead wire supply systems – 15kV DC and 30kV DC.

 600V - 750V DC volt range is used for third rail systems (additional rail is provided for supplying electricity to train and is called conductor rail).

 Disadvantages: -

1. expensive substations are required at frequent intervals.

 2. The overhead wire or third rail must be relatively large and heavy.

 3. Voltage goes on decreasing with an increase in length

AC Traction

 AC Traction units draw alternating currents from an overhead line.

 Typical Voltages Used are:- 25 kV AC, 50 Hz 25 kV AC, 60 Hz

Advantages:-

1. Fewer substations are required.

 2. Lighter overhead current supply wire can be used.

 3. Reduced weight of support structure.

 4. Reduced capital cost of electrification

Multi-Systems

Multi-system trains are used to provide continuous journeys along routes that are electrified using more than one system.

1. One way to accomplish this is by changing locomotives at the switching stations.

2. These stations have overhead wires that can be switched from one voltage to another.

3. Another way is to use multi-system locomotives that can operate under several different voltages and current types.