DIESEL LOCOMOTIVE

The locomotives of INDIA presently consist of electric and diesel locomotives. Steam locomotives are no longer used in INDIA , except in heritage trains. A locomotive is also called loco or engine.

 The Bengal sappers of the INDIAN ARMY were the first to run a steam locomotive in INDIA. The steam locomotive named ‘Thomason’ ran with two wagons for carrying earth from Roorkee to Piran kalivar in 1851, two years before the first passengers train ran from Bombay to Thane in 1853.

The diesel locomotives

The modern diesel locomotives is a self-contained version of the electric locomotive. Like the electric locomotive, it has electric drive in the form of traction motors driving the axles and controlled with electronic controls. It differs principally in that it carries its own generating station around with it, instead of being connected to a remote generating station through overhead wires.

Diesel locomotives use electricity drive forward motion despite the name ‘diesel’. A large diesel engine turns a shaft that drives a generator which makes electricity. This electrical energy powers large electric motors at the wheels called ‘traction motors’. A fuel tank is also essential. It is interesting to note that the modern diesel engine locomotive produces about 35% of the power of electric locomotive of similar weight.

COMPONENTS AND WORKING OF A DIESEL LOCOMOTIVE

Diesel Engine

This is the main power source for the locomotive.  It comprises a large cylinder block, with the cylinders arranged in a straight line or in a V .  The engine rotates the drive shaft at up to 1,000 rpm and this drives the various items needed to power the locomotive.  As the transmission is electric, the engine is used as the power source for the electricity generator or alternator, as it is called nowadays.

Main Alternator

The diesel engine drives the main alternator which provides the power to move the train.  The alternator generates AC electricity which is used to provide power for the traction motors mounted on the trucks (bogies).  In older locomotives, the alternator was a DC machine, called a generator.  It produced direct current which was used to provide power for DC traction motors.  Many of these machines are still in regular use.  The next development was the replacement of the generator by the alternator but still using DC traction motors.  The AC output is rectified to give the DC required for the motors.
  For more details on AC and DC traction, see the Electronic Power Page on this site

Auxiliary Alternator

  This provides AC power for lighting, heating, air conditioning, dining facilities etc. on the train.  The output is transmitted along the train through an auxiliary power line.

Motor Blower

The diesel engine also drives a motor blower.  As its name suggests, the motor blower provides air which is blown over the traction motors to keep them cool during periods of heavy work.  The blower is mounted inside the locomotive body but the motors are on the trucks, so the blower output is connected to each of the motors through flexible ducting.  The blower output also cools the alternators.  Some designs have separate blowers for the group of motors on each truck and others for the alternators.

Rectifiers/Inverters

The output from the main alternator is AC but it can be used in a locomotive with either DC or AC traction motors.  DC motors were the traditional type used for many years but, in the last 10 years, AC motors have become standard for new locomotives.  They are cheaper to build and cost less to maintain and, with electronic management can be very finely controlled.
 To see more on the difference between DC and AC traction technology try the Electronic Power Page on this site.      
To convert the AC output from the main alternator to DC, rectifiers are required.  If the motors are DC, the output from the rectifiers is used directly.  If the motors are AC, the DC output from the rectifiers is converted to 3-phase AC for the traction motors. 

Electronic Controls

Almost every part of the modern locomotive's equipment has some form of electronic control.  These are usually collected in a control cubicle near the cab for easy access.  The controls will usually include a maintenance management system of some sort which can be used to download data to a portable or hand-held computer.      

Batteries

Just like an automobile, the diesel engine needs a battery to start it and to provide electrical power for lights and controls when the engine is switched off and the alternator is not running.

Traction Motor

Since the diesel-electric locomotive uses electric transmission, traction motors are provided on the axles to give the final drive.  These motors were traditionally DC but the development of modern power and control electronics has led to the introduction of 3-phase AC motors.
For a description of how this technology works, go to the Electronic Power Page on this site.
There are between four and six motors on most diesel-electric locomotives.  A modern AC motor with air blowing can provide up to 1,000 hp.      

Pinion/Gear

The traction motor drives the axle through a reduction gear of a range between 3 to 1 (freight) and 4 to 1 (passenger).

Fuel Tank

A diesel locomotive has to carry its own fuel around with it and there has to be enough for a reasonable length of trip.  The fuel tank is normally under the loco frame and will have a capacity of say 1,000 imperial gallons.  In addition to fuel, the locomotive will carry around, typically about 300 US gallons of cooling water and 250 gallons of lubricating oil for the diesel engine.

Air Reservoirs

Air reservoirs containing compressed air at high pressure are required for the train braking and some other systems on the locomotive.  These are often mounted next to the fuel tank under the floor of the locomotive.

Air Compressor

The air compressor is required to provide a constant supply of compressed air for the locomotive and train brakes. 

Drive Shaft

The main output from the diesel engine is transmitted by the drive shaft to the alternators at one end and the radiator fans and compressor at the other end. 

Gear Box

The radiator and its cooling fan is often located in the roof of the locomotive.  Drive to the fan is therefore through a gearbox to change the direction of the drive upwards.

Radiator and Radiator Fan

The radiator works the same way as in an automobile.  Water is distributed around the engine block to keep the temperature within the most efficient range for the engine.  The water is cooled by passing it through a radiator blown by a fan driven by the diesel engine.
 See Cooling for more information.

Turbo Charging

The amount of power obtained from a cylinder in a diesel engine depends on how much fuel can be burnt in it.  The amount of fuel which can be burnt depends on the amount of air available in the cylinder.  So, if you can get more air into the cylinder, more fuel will be burnt and you will get more power out of your ignition.  Turbo charging is used to increase the amount of air pushed into each cylinder.  The turbocharger is driven by exhaust gas from the engine.  This gas drives a fan which, in turn, drives a small compressor which pushes the additional air into the cylinder.  Turbocharging gives a 50% increase in engine power.
The main advantage of the turbocharger is that it gives more power with no increase in fuel costs because it uses exhaust gas as drive power.  It does need additional maintenance, however, so there are some type of lower power locomotives which are built without it.

Sand Box

Locomotives always carry sand to assist adhesion in bad rail conditions.  Sand is not often provided on multiple unit trains because the adhesion requirements are lower and there are normally more driven axles.

Truck Frame

This is the part  carrying the wheels and traction motors of the locomotive.
 for more infomation about Bogie Parts Page or the Wheels and Bogies Page on this site.

 

Diesel-Electric Types

Diesel-electric locomotives come in three varieties, according to the period in which they were designed.  These three are:
DC - DC (DC generator supplying DC traction motors);
AC - DC (AC alternator output rectified to supply DC motors) and
AC - DC - AC (AC alternator output rectified to DC and then inverted to 3-phase AC for the traction motors). 



DIESEL LOCOMOTIVES IN INDIA

In India, locomotives are classified according to their track gauge, motive power, the work they are suited for and their power or model number. The class name includes this information about the locomotive. It comprises 4 or 5 letters. The first letter denotes the track gauge. The second letter denotes their motive power (Diesel or Electric) and the third letter denotes the kind of traffic for which they are suited (goods, passenger, mixed or shunting). The fourth letter used to denote locomotives' chronological model number. However, from 2002 a new classification scheme has been adopted. Under this system, for newer diesel locomotives, the fourth letter will denote their horsepower
range. Electric locomotives don't come under this scheme and even all diesel locos are not covered. For them this letter denotes their model number as usual.

Classification syntaxes

The first letter (gauge)

• W – Indian broad gauge (the "W" Stands for Wide Gauge - 5 ft 6 in)
• Y – metre gauge (the "Y" stands for Yard Gauge - 3 ft or 1000mm)
• Z – narrow gauge(2 ft 6 in)
• N – narrow gauge (toy gauge) (2 ft)

The second letter (motive power)

• D – diesel
• C – DC electric (can run under DC overhead line only)
• A – AC electric (can run under AC overhead line only)
• CA – both DC and AC (can run under both AC and DC overhead line); 'CA' is considered a single letter
• B – Battery electric locomotive (rare)

The third letter (job type)

• G – goods
• P – passenger
• M – mixed; both goods and passenger
• S – shunting (also known as switching engines or switchers in the USA and some other countries)
• U – multiple units (EMU/DMU)
• R – Railcars

For example, in "WDM 3A":

• "W" means broad gauge
• "D" means diesel motive power
• "M" means suitable for both goods and passenger service
• "3A" means the locomotive's power is 3,100 hp ('3' stands for 3000 hp, 'A' denotes 100 hp more)

Or, in "WAP 5":

• "W" means broad gauge
• "A" mean AC electric traction motive power
• "P" means suitable for Passenger service

"5" denotes that this locomotive is chronologically the fifth electric locomotive model used by the railways for passenger service.

Classification codes of diesel traction loco

• WDM – Wide Diesel Mixed
• WDP – Wide Diesel Passenger
• WDG – Wide Diesel Goods
• WDS – Wide Diesel Shunter
• WCDS – Wide Converted Diesel Shunter

Passenger locomotives

WDP 1 (Bo-Bo bogies. 80 tons weight. Rated speed of 140 kmph. 12 cylinder engine. 2300 hp. Built by DLW in 1970. Homed at Vijayawada and Tughlakabad sheds only.

WDP 2(This locomotives are actually prototypes of the class WDP 1 and never entered serial production. Designed in 1996 by DLW. 2300 hp. Co-Co bogies. )

WDP 3(New class name WDP 3A. Dedicated passenger diesel locomotive. Entered service in 1998. Max speed 140kmph. Built by DLW. 29.25 tons of tractive effort. 3100 hp)

WDP 4 (EMD (former GM-EMD) GT46PAC, fundamentally a passenger version of the WDG 4 (GT46MAC). 4000 hp)

WDP 4B (EMD (former GM-EMD) GT46PAC, An improved version of the WDP 4, this is a more powerful version and has 6 traction motors, just like the WDG 4. Also comes with wider cabin to aid visibility and minor exterior design changes.As of now,serial production of the single cab locomotives has been stopped. 4500 hp)

WDP 4D (EMD (former GM-EMD) GT46PAC, This is basically a WDP 4B with twin cabs. Minor changes were made to the locomotive to facilitate the addition of a second cabin. This locomotive comes with LCD instrument display and toilet for the drivers. Has entered serial production and regular service. 4500 hp.

via- wikipedia,rail technical