2. Introduction
• The traction machine shed was established in year 1973 as a unit of Electric Loco Shed, Kanpur and later on
18/01/74, it was made independent unit.
• This shed was commissioned primarily to meet the imperative maintenance needs of electric loco motors.
• At present the scope of work includes following:-
• Reclamation/rewinding of armature and stator of traction motor and other auxiliary machines of electric
locos & EMU for various sheds of Indian Railways, rewinding of loco auxiliary machines and other general
power electrical machines of Northern Railways, India.
• Reshafting of armatures and associated activities.
• Stator coil manufacturing for TAO and HITACHI traction motors.
3. Different Types of Locomotives
• Steam Locomotives
• Diesel Locomotives
• Electric Locomotives
4. Steam Locomotives
• Steam locomotive played a key role during development and golden age of
railroading. Steam locomotive is a self contained power unit consisting of a steam
engine , a boiler with fuel and water supplies. Superheated steam is admitted to the
cylinders by a suitable valve arrangement and the pressure on the pistons being
transmitted through main rod to the driving wheels.
• Disadvantages:
• It has strictly limited overload capacity.
• It has very low thermal efficiency of about 6-8% because installation of a
condenser on locomotive is very difficult
5. Diesel Locomotives
• Diesel electric locomotives were introduced firstly in united states in 1924
and have become the most widely used type of locomotive. It was
introduced for first time in India in 1958. Diesel electric locomotive has
electric drive in form of traction motors driving the axles and controlled
with electronic controls.
• It differs from electric locomotives principally in that it has its own
generating station instead of being connected to a remote generating station
through overhead wires. The generating station consists of a large diesel
engine coupled to dc generator that provides power to traction motors.
6. Electric Locomotives
• Electric locomotives generally have two or more dc or ac motors. In these
locomotives , power is collected from an electric trolley which is running on
an overhead wire. The overhead wire can carry both types of supply ac as
well as dc. Indian railway also uses both types of supply systems :
• (a) AC system- 25 kv single phase 50 hz ac supply
• (b) DC system- 1500 V dc supply.
Only western zone and central zone of railway uses dc system.
8. Traction Motor• The traction motor is a four pole DC series motor in which field winding is connected
in series with armature.
• An electric locomotive as well as diesel-electric locomotive in indian railway contain
six dc traction motors at once.
9. Construction
• The armature core is made from high permeability silicon steel stampings and these stampings are
separated by thin coating of varnish as insulation with each other.
• The commutator is built up with hard drawn silver bearing copper segment which are insulated with
micanite segment.
• After the commutator is statically and dynamically seasoned to insure stability ,the complete armature
is dynamically balanced.
• The main poles are built from steel laminations. There are four brush holder per motor, each carrying
3 split carbon brushes. Each brush holder is carried on two insulated support pins.
• The armature is supported on grease lubricated roller bearing. Bearing assemblies are sealed type, so
necessity of lubrication in about 2 or 3 years.
10. Working of Traction Motors
• To understand the operation of a traction motor, three transition panels are studied. Transition panels
perform transition events. These events correspond to field weaking and changing the connections of
traction motor.
• Three transition panels are performed at three different speeds –
• First transition at 30 km/hr speed
• Second transition at 50 km/hr speed
• Third transition at 80 km/hr speed
When dc supply is provided to circuit of traction motors, a large current flows through armature of motor as
it is connected in series with field. As a result armature, armature begins to rotate and a back emf is generated
which opposes the main supply voltage. ( back emf Eb = PφNZ/60A Eb α N ) As speed increases, back emf
also increases and it offers resistance to flow of generated current to traction motors. Hence for increasing the
speed , the supply voltage must increase but it is not possible to increase supply above rated voltage.
11. Different Transitions at Different Speeds
• When speed is reached at 30 km/hr, first transition panel is switched on. Now a
parallel combination of two series connected traction motors is under operation and
resistance is connected in parallel with the field of motors to refuse back emf.
• When speed increases beyond 40 km/hr and back emf again starts increasing
rapidly. So second transition panel is switched on at speed of 50km/hr. After
second transition, all six motors run in parallel, without resistance parallel to field of
motors.
• Third transition panel is switched on at speed of 80 km/hr. By this transition,
resistances are connected parallel with field of motors in circuit of second transition
to reduce back emf.
12. Braking
• Dynamic or rheostatic braking is employed for electric locomotives. During the time
of braking, traction motors are disconnected from supply and is connected to a
dynamic resistance.
• Now traction motors are acted as traction generator because kinetic energy is
converted into electrical energy. The direction of current is reversed during this
period as before braking.
• Field current also reverses as field winding is connected in series with armature.
• Hence connections of field winding should be changed such that current flows in it
in should be changed such that current flows in it in same direction as before
braking
14. Auxiliary Motor
• Auxiliary converter forms part of the auxiliary drive system in the ac
locomotive which is primarily used for supplying power to loads such as fans,
blowers, lighting the cabin and also charging the locomotive battery. Its
typically of IGBT configuration and is fed from the auxiliary winding of the
locomotive transformer.
• It is also used for cooling purpose of traction motors, special section of
auxiliary motor is made which is used for cooling purposes.
