25-01-2013, 12:38 PM
DIESEL LOCOMOTIVE WORKS, VARANASI
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INTRODUCTION
Diesel Locomotive Works (DLW) is a production unit under the Ministry of Railways.
This was setup in collaboration with American Locomotive Company (ALCO) USA in
1961 and the first locomotive was rolled out in 1964. To meet the growing traffic
requirement, Indian railways entered into contract for supply of state of art High HP
locomotives and signed transfer of technology agreement with Electro Motive Division of
General Motors, USA. DLW started manufacturing these fuel efficient locomotives in
2001-02. These locomotives are microprocessor controlled and have greater reliability &
require less maintenance.
Over the years DLW's production capacity has progressively increased. During the year
2010-11, DLW made record by producing 258 locomotives. Besides meeting the diesel
locomotive requirement of Indian Railways, DLW also caters to export market.
How a locomotive works
The EMD locomotive is equipped with a 4500 hp two stroke diesel engine which drives
the main traction alternator. The main alternator converts diesel engine mechanical
power into alternating current (AC) electrical power. The internal rectifier banks of the
main alternator convert alternating current to direct current (DC) thereby providing a DC
power output. The DC output from the main alternator is called the DC link voltage and
is applied to the traction inverters (TCC).The inverters change DC link voltage into
variable voltage, variable frequency, 3 phase AC power. There are two traction
inverters, each supplying AC power to parallel set of three induction traction motors.
Each traction motor drives the locomotive wheels through a set of gear& pinion. There
are two bogies each having three traction motors & three wheel sets.
Alternator
An alternator converts kinetic energy (energy of motion) into electrical energy. All
recently manufactured automobiles rely on alternators to charge the battery in the ignition
system and supply power to other electrical equipment.
Alternators are sometimes called AC generators because they generate alternating
current (AC).
Electric current can be generated in two ways: The magnet may rotate inside the coil, or the coil
may rotate in a magnetic field created by a magnet. The component that remains stationary is
called the stator, and the component that moves is called the rotor. In alternators, the coil is the
stator and the magnet is the rotor. A source of mechanical power, i.e. the diesel engine turns the
rotor.
In WDM-3D and WDM-3A locos, the diesel engine’s mechanical output is used to run the
shaft of the Alternator. The alternating output of the Alternator is then rectified to DC
via solid-state rectifiers and is fed to traction motors (DC) that run the loco wheels.
Thus they operate on AC-DC Traction mechanism. WDG4 and WDP4 locos have AC-AC
traction with microprocessor control, i.e. AC Traction motors are used thus eliminating
the motor commutator and brushes The result is a more efficient and reliable drive that
requires relatively little maintenance and is better able to cope with overload conditions.
Traction Motor
It’s an electric motor providing the primary rotational torque of the engine, usually for
conversion into linear motion (traction).
Traction motors are used in electrically powered rail vehicles such as electric multiple
units and electric locomotives, other electric vehicles such as electric milk floats,
elevators and conveyors as well as vehicles with electrical transmission systems such as
diesel-electric and electric hybrid vehicles. Traditionally, these are DC series-wound
motors, usually running on approximately 600 volts, but now a days using 3-phase ac traction
motor.
Cylinder Diesel Engine
It is an internal-combustion engine in which heat caused by air compression ignites the
fuel. At the instant fuel is injected into a diesel engine’s combustion chambers, the air
inside is hot enough to ignite the fuel on contact. Diesel engines, therefore, do not need
spark plugs, which are required to ignite the air-fuel mixture in gasoline engines. The
Diesel engine has 16 cylinders. Pistons inside the cylinders are connected by rods to a
crankshaft. As the pistons move up and down in their cylinders, they cause the crankshaft to
rotate. The crankshaft’s rotational force is carried by a transmission to a drive shaft, which turns
axles, causing mechanical output.