Driving forward of vehicle is called traction and
the system, which employs this type of mechanism is
called Traction system.
Classified broadly into groups namely:
Electric traction system.
The system which use electrical power for traction
system i.e. for railways, trams, trolleys, etc. is
called electrical traction.
Electric traction means a location in which the
driving force is obtained from electric motors.
Electric traction will continue to play a dominant
role in the railways since it is an environmentally
clean technology compare to diesel traction and
also its running cost is low.
There are many advantages of electric traction over
other forms of locomotion.
traction efforts should be exertion at
starting in order to have rapid acceleration.
Equipment should be capable of overloads for short
The wear caused on the track should be minimum.
Braking should be possible without excessive wear
on the brush.
Capacity of withstanding voltage fluctuation and
temporary interruption of supply.
Parallel running usually more than one motor (two
or four) should be possible.
Cheapness : It is cheapest method if all methods of
Cleanliness : It is free from smoke and flue gasses.
Maintenance cost : Maintenance and repair cost is about
50% of steam traction system.
Starting time : It can be started without loss of time.
High starting torque : This system uses of D.C & A.C series
motor, which has a very high starting
Braking : In electric traction, regenerative breaking is used
which feeds back 40% of the energy.
Saving in high grade coal : No coal is required for electric
High initial expenditure.
Failure of supply is a problem.
Electrically operated vehicles have to move only on
For braking & control, addition equipments
Interference with telegraphs and telegraph lines.
II. A.C. system.
i. There phase A.C. system.
ii. Single phase standard frequency system.
iii. Single phase low frequency system.
iv. Single phase to three phase system [kondo
e.g:600v dc is given to tramways and trolley
In general following electric system exist:
AC 3 phase 3.7 kV system.
AC single phase 15/16 kV-161/25 Hz.
AC single phase 20/25 kV-50/60 Hz.
DC 600 V.
DC 1200 V.
DC 1.5 Kv.
DC 3 Kv.
Light overhead catenary.
Saving in sub-station.
Lesser equipment used & easy to maintain.
Cheap as far as cost for fixed installation.
Single-phase A.C. system imposes unbalancing effect
2. Produces interference with telecommunication
Scheme of AC Electric locomotive power system
with Thyristor control and separately excited DC