ELECTRIC TRACTION SYSTEM
Act of drawing or state of being drawn propulsion
of vehicle is called tractions. There are various systems of
traction prevailing in our country such as steam engine
drive, electric drive. These systems of tractions may be
classified broadly into groups namely
1) The traction system which do not involve the use of
electricity at any stage and called as non-electric tractions
system such as steam engine drive, IC engine drive etc.
2) The tractions system which involves the use of
electricity at some stage and called as electric tractions.
System such a diesel electric drive, electric drive etc.
Systems of track electrification:
1.Dc system.
2.Single phase ac system.
3.three-phase ac system.
4.Composite system
(a). kando system.
(b). single phase to dc system.
Existing Tractions System
Existing tractions system uses D.C. motors.
a) The 25 KV over head voltage is step down to 2000 V
with the help of step down transformer.
b) Rectifier rectifies this A.C. voltage to D.C. voltage.
c) This rectified D.C. voltage is used to operate the D.C.
motors in existing system engine.
Causes favoring the DC motors
a) D.C. series motors are less costly, however for some
H.P more efficient and requires less maintenance than
A.C. series motor.
b) Rail conductor system of track electrifications which is
less costly with D.C. system than with A.C. System
Electric traction motors
General features of traction motors:
 Mechanical features
 Electrical features
Braking:
Generally braking is classified into two types in the
traction.
 Electrical braking.
 Plugging
 Rheostatic or dynamic braking.
 Regenerative braking.
 Mechanical braking.
 Compressed air brakes
 Vacuum brakes
 Hydraulic brakes
Requirements of braking:
 The braking should be simple and reliable in action
 The braking should be smooth so as to avoid damage
of goods.
 Maintenance needs should be minimum.
 The braking force applied to each axle should be
proportional to axle load so as to obtain uniform
deceleration.
Power supply for electric traction
 Electric trains in India first introduced in Bombay sub urban services in 1925
and in madras in 1931. at that time the system adopted was 1500v dc.
 In earlier days many of the systems used for electrification of railways in
India and other countries such as America, France Hungary etc.
 From the reports obtained from French national railways the single phase ac
system with 50hz frequency is more advantageous both financial and
operation.
 In India in 1957 for the first time adopted the system has 25kv, 50hz
frequency, single-phase system.
High voltage ac supply
Arrangement of power supply in India are as follows:
The power is purchased from the authorities who are
responsible for the operation and maintenance of 220/132
transmission lines up to 25 kv outgoing terminals of
substations. How ever 25 kv ckt breaker is controlled
from remote control center by Tpc.
The 220/132 kv equipment is maintained by the
transmission authorities and 25 kv breakers are owned and
maintained by the railway authorities.
Current collectors for OHS:
In over head system the current collectors are shown
below:
 trolley collector.
 bow collector.
 pantograph collector.
Over head construction in railways
Loco Transformer
This is a main transformer
of locomotive. The 25 KV
single phase AC power
supply of OHE is fed to the
winding
of
regulating
transformer through main
bushing. The winding is
equally divided into 32
taps. These taps are
connected to tap changer.
Traction transformer
There are two traction transformer connected in parallel of
same rating for the purpose of reliability the rating of
transformer are as follows
Capacity
Frequency
taps on HT
cooling
: 25 KV.
: 50 Hz
: 32 taps
:forced oil & air
Arno Converter
1.
2.
3.
Arno converter is a device
which convert single phase
AC in to three phase AC.
The three phase supply
needed for the three phase
induction motors which used
in blowers, exhausters an oil
pumps. To supply three phase
power to three phase
induction
motors
arno
converter is used.
Arno converter is rotating
device.
DC link
 This is essentially a bank of capacitor and inductor
or active filter circuitry to further smooth.
 Also to trap harmonics generated by drive
converter and traction motors.
Power supply for signaling
For the purpose of signaling and reliable operation the
25 KV is converted to 240 V through auxiliary
transformer by tapping 25 KV OHE at the places where
needed.
Transmission Path
Under ground telecommunication trunk cable is provided for
transmitting the signals from and to the Remote Control
Centre (RCC) and the controlled Remote Terminal Units
(RTU). Three pairs of conductors (one pair for send one pair
for receive and the third as spare) from this cable are made
available for remote control operation.
Reference:
Utilization of electric power
&
Electric Traction
by
J.B.Gupta