Diesel Locomotive Structures PDF

# Diesel Locomotive Structures ## PUP Civil Engineering Department #WeLearnAsOne ## 1 Diesel Locomotive Structures ### 1.1 How Diesel Locomotive Works - Diesel engines are used in many types of vehicles, including locomotives. - They have a fuel efficiency 20 percent greater thermally than a gas...

# Diesel Locomotive Structures ## PUP Civil Engineering Department #WeLearnAsOne ## 1 Diesel Locomotive Structures ### 1.1 How Diesel Locomotive Works - Diesel engines are used in many types of vehicles, including locomotives. - They have a fuel efficiency 20 percent greater thermally than a gas engine. - This means a 20 percent increase in fuel economy and therefore lower operating costs than those of a gas engine. - Diesel engines also last longer than gas engines because they run at a much slower rpm (revolutions per minute) rate than gas engines do. - The hybrid diesel locomotive combines a huge, 12- to 16-cylinder, two-stroke diesel engine, with some heavy-duty electric motors and generators, throwing in a little bit of computer technology. **Why Hybrid? Why Diesel?** - The main reason why diesel locomotives are hybrid is because this combination eliminates the need for a mechanical transmission. - Diesel engines are more efficient than gasoline engines. - Train manufacturer CSX estimates that their fleet moves 1 ton (0.9 metric tons) of cargo an average of 492 miles (791 kilometers) per 1 gallon (4 liters) of fuel, making locomotives four times as efficient as moving goods on roadways. - Diesel-electric systems are also five times more efficient than the old steam engine locomotives, which is why diesel entirely replaced steam in the early 20th century. - Diesel has seen competition from fully electric trains, which pull directly from a power grid as they drive. - This method is several times more efficient than burning any kind of onboard fuel to produce energy. - Electric locomotives are especially popular in Europe and Asia, but the changeover in the U.S. has been slow. - Probable causes are that electric trains require their own specialized infrastructure to operate, and old locomotives can be in service for multiple decades before retirement. - Diesel remains the standard. - A few passenger railways have however been electrified in the States, including Amtrak's northeast corridor and California commuter rail. **Steel Wheels** - Trains have steel wheels to reduce rolling friction. - About 4-7 percent of its potential energy is lost to the rolling resistance of the tires. - Tires bend and deform a lot as they roll, which uses a lot of energy. - The amount of energy used by the tires is proportional to the weight that is on them. - Since a car is relatively light, this amount of energy is acceptable. - Since a train weighs thousands of times more than a car, the rolling resistance is a huge factor in determining how much force it takes to pull the train. - The steel wheels on the train ride on a tiny contact patch — the contact area between each wheel and the track is about the size of a dime. - By using steel wheels on a steel track, the amount of deformation is minimized, which reduces the rolling resistance. - A train is about the most efficient way to move heavy goods. - The downside of using steel wheels is that they don't have much traction. **Traction** - Traction when going around turns is not an issue because train wheels have flanges (projecting rims around the wheels) that keep them on the track. - A locomotive can generate more than 60,000 lb-ft of torque. - The eight wheels on the locomotive have to be able to apply it to the track without slipping. - The locomotive uses a neat trick to increase the traction: sand is sprayed in front of each wheel. - Sand dramatically increases the traction of the drive wheels. - The train has an electronic traction-control system that automatically starts the sand sprayers when the wheels slip or when the engineer makes an emergency stop. - The system can also reduce the power of any traction motor whose wheels are slipping. ### 1.2 Different Location and Parts of the Locomotive **Figure 1.2.2** | Number | Part | |---|---| | 1 | Head light | | 2 | Inertial Filter Air Inlet | | 3 | Starting Fuse and Battery Knife Switch | | 4 | Handrails | | 5 | Cooling System Air Inlet | | 6 | Radiator and Fan Access | | 7 | Coupler "E/F" Type | | 8 | Sanding Box (8) | | 9 | Jacking Pads (4) | | 10 | Wheels (6) | | 11 | Fuel Tank | | 12 | Compressed Air System Main Reservoirs | | 13 | Battery Box | | 14 | Trucks (3 axle 3 motor HTSC type) Qty. 2 | | 15 | Under frame | | 16 | Dynamic Brake Grids | | 17 | Dynamic Brake Fans (2) | **Figure 1.2.3** | Number | Part | |---|---| | 1 | Electrical Control Cabinet | | 2 | Fuel Pump | | 3 | Engine Starting Motors | | 4 | Traction Control Cabinet | | 5 | Traction Motor Cooling Air Blower | | 6 | Main Generator/Companion Alternator Blower | | 7 | Engine Exhaust Stack | | 8 | Engine Exhaust Manifold | | 9 | 16-710G3B Diesel Engine | | 10 | Governor | | 11 | Engine room Vent | | 12 | Engine Water Tank | | 13 | Lube Oil Cooler | | 14 | Primary Fuel Filter | | 15 | Air Compressor | | 16 | Radiators | | 17 | AC Radiator Cooling Fans (2) | | 18 | Draft Gear | | 19 | Air Compressor Air Filter | | 20 | Lube Oil Filter Tank | | 21 | Lube Oil Strainer | | 22 | Lube Oil Sump | | 23 | Main Generator/ Companion Alternator | | 24 | Electrical Control Cabinet Air Filter Box | | 25 | Traction Motors (6) | **Figure 1.2.4** | Number | Part | |---|---| | 1 | Air Brake Rack | | 2 | Engineers Control Console | | 3 | Cab Door | | 4 | Traction Control Cabinets | | 5 | Inertial Air Filters | | 6 | TCC Electronics Blower | | 7 | Engine Air Filter | | 8 | Radiators | | 9 | Engine | | 10 | AC Auxiliary Generator | | 11 | Inertial Filter Dust Bin Blower and Motor | | 12 | Electrical Control Cabinet | | 13 | Cab Seat | - The main engine in this locomotive is a Caterpillar EMD 710 series engine. - The "710" means that each cylinder in this turbocharged, two-stroke, diesel V-12 has a displacement of 710 cubic inches (11.6 liters). - This is more than double the size of most of the biggest gasoline V-8 car engines — and we're only talking about one of the 12 cylinders in this 3,300-hp engine. - So why two-stroke? - Even though this engine is huge, if it operated on the four-stroke diesel cycle, like most smaller diesel engines do, it would only make about half the power. - This is because with the two-stroke cycle, there are twice as many combustion events (which produce the power) per revolution. - It turns out that the diesel two-stroke engine is really much more elegant and efficient than the two-stroke gasoline engine. ## 2 Systems Inside Locomotives ### 2.1 Fuel Oil System - The fuel oil system is designed to supply fuel to the engine in correct quantity and at the right time according to the engine requirements. - The fuel oil system draws fuel from fuel tank, filter the fuel, pressurize the fuel, and inject the fuel into the engine in correct quantity in atomized condition. **Fuel oil system consist of:** - Fuel feed system - Fuel injection system **1. Fuel feed system:** - Fuel is drawn from the fuel oil tank through a suction strainer by the fuel pump. - The strainer separates foreign particles from the fuel oil, and protects the fuel pump. - The pump is designed to supply adequate quantity of fuel to the engine at various speeds and load conditions. - Fuel then goes to primary fuel filter. - This primary filter is provided with a 30-PSI bye pass valve with sight glass, which should be normally empty. - Whenever the primary filter is Choked/clogged and the pressure difference reaches 30 PSI this lye-pass value open allowing the fuel oil directly to the system, which can be noticed by the flow of bye-pass fuel in the sight glass. - Under such cases the primary filter element is changed. - The fuel then passes to 02 engine mounted secondary filters, which are of spin-on type. - Secondary fuel filters are also provided with a bye-pas value, which is set at 60 PSI. - Whenever the filters are choked/clogged and the pressure difference across the secondary filters reaches 60 PSI, this lye-pass valve opens and diverts the fuel oil back to fuel tank, avoiding damage to fuel injectors due to unfiltered fuel oil. - A lye-pass sight glass is also provided to indicate the condition of the fuel secondary filters and the sight glass should be normally empty. - From the secondary filters the fuel oil is supplied to all unit injectors through fuel supply manifolds located inside the top deck on the both banks. - The governor controls the quantity of fuel to be injected through the injectors to the engine. **Secondary fuel oil filter** - At the end of the fuel supply manifolds, a regulating valve with a sight glass is provided which is set to 10 PSI. - The regulating valve ensures constant fuel supply to all unit injector in all working conditions. - If the system is working properly the sight glass should indicate clear and clean fuel oil flow all the Secondary fuel oil filter. - Air bubbles, interrupted fuel flow or no fuel flow in the return sight glass indicates problem in the fuel feed system. **2. Fuel injection system:** - Fuel supplied by the fuel feed system is always available at all the unit fuel injectors. - The fuel oil available at each injector are to be pressurized to very high pressure, timed, and injected in the cylinder in atomized form. - The timing of each unit injector is decided by the camshaft and the fuel is pressurized by the in-built fuel injection pump which is operated by individual cam lobe of the cam shaft. - The quantity of fuel to be injected will be regulated and controlled by engine mounted wood word governor according to the notch and load conditions. - The governor operates fuel control shaft, linkage mechanism and fuel racks. - The individual fuel injector nozzle does the atomization of the fuel to be injected in the cylinder. ### 2.2 Cooling Water System - Engine cooling water system is a closed loop pressurized water-cooling system. - The water-cooling system cools: all the engine cylinder liners, cylinder heads, after cooler, lube oil cooler and compressor. **LINE DIAGRAM OF THE COOLING WATER SYSTEM** - In the water-cooling system, there are 02 nos. engine mounted water pumps (centrifugal type). - The water pump receive water from the radiator through lube oil cooler. - Water from the water pump is sent to the two (left and right Bank) water main header (also called water inlet manifold). - From the water main header water enter to all the cylinder liner jackets through water jumper. - After cooling the cylinder liners water enter in the cylinder head through 12 holes which are matched to cylinder liner with "O" rings and cools the combustion chamber of the cylinder head. - Outlet water from each cylinder head goes to the return header (also called water outlet manifold) which carry water to the radiator. - Each water main header is connected at the rear end from where a water pipe line carry water to cool the after cooler. - Water from the aftercooler goes to water return header and through water return header to radiator. - A water pipe line from the water pump carry water to compressor to cool the compressor liners, cylinder head, valves and the compressed air inside the inter cooler. - Air compressor cooling is done whenever engine is running. - The radiators are located in a hatch at the top of the long hood end of the locomotive. - The hatch contains the radiator assemblies, which are grouped in two banks. - Each radiator bank consists of two quad length radiator core assemblies, bolted endto-end. - Headers are mounted on the radiator core to form the inlet and outlet ends of the radiator assembly, a bypass line is provided between the inlet and outlet lines in order to reduce velocity in the radiator tubes. - Two 8-blade 52" cooling fans, which operate independently, are located under the radiators in the long hood carbody structure. - They are numbered 1, and 2, with the No. 1 fan being closest to the driver cab. - The water pump inlet side is connected to an expansion tank for makeup water in the water system. - The expansion tank is located in the equipment rack. **Temperature control by the cooling system:** - Mainly the two electronic temperature sensing probes (ETP1& ETP 2), EM2000 computer and the radiator fans take part in controlling the water temperature. - Two electronic temperature-sensing probes (ETP1& ETP 2) are located in the water pipe line between the lube oil cooler to the inlet of the water pump on the engine left side. - Temperature probe readings are converted by ADA Module from analog to digital signals which are used by the EM2000 to control all cooling functions. - Each cooling fan is driven by a two-speed AC motor, which in turn is powered by the companion alternator. - As the engine coolant temperature rises, the fans are energized in sequence by the control computer (slow speed). - As additional cooling is required, the fans switch to full speed in progression as coolant temperature rises. - As coolant temperature drops, the fans switch off one at a time. - The cooling fans are controlled by the computer which act on the contactors. - The computer also controls the fan sequencing duty cycle and speed (low or high) to ensure even fan and contactor wear. - The engine water temperature can be observed by a gauge located on the inlet line to water pump. - The gauge is colour coded to indicate cold (Blue), normal (green) and hot (red). - When the engine temperature become excessively high, the EM 2000 will display "HOT ENGINE"- and throttle 6 limit" message. - The computer will initiate the reduction in engine speed and load upto 6th notch. - This condition will remain in effect until the temperature return to safe limit. - If the engine water temperature is below 115 0 F (460 C), the engine speed will be raised to throttle 2 automatically by the computer. - Once the engine water temperature reaches above 125 0 F (52 0 C), the engine speed will be reduced to IDLE. - The reason for engine speed up will be displayed to the driver on EM 2000 computer monitor as "Engine speed increase- low water temperature". **Cooling System Pressurization:** - The cooling system is pressurized to raise the boiling point of cooling water. - This in turn permits higher engine operating temperatures, with a minimum loss of coolant due to pressurization and also ensures a uniform water flow. - This minimizes the possibility of water pump cavitation during transient high temperature conditions. - A pressure cap, which is located on the water tank filling pipe, opens at approximately 20 PSI. - It prevents the damages of cooling system components by relieving excessive pressure from the system. - The pressure cap is equipped with a handle which helps installing and removing of the cap. - The most important function of the pressure cap handle is to release pressure developed in the water system before removing the pressure cap. ### 2.3 Lube Oil System - The complete engine lubricating oil system is a combination of 04 oil systems. - These are: - Scavenging oil system - Main lubricating oil system - Piston cooling oil system - Soak Back or turbo lube system **1. Scavenging oil system** - The scavenging oil pump is a positive displacement, helical gear type pump. - This pump takes lube oil from 02 sources- from the engine oil sump and from the oil strainer. - The pump feed lube oil to lube oil filter tank (also called Michiana oil filter). - Oil from the filter tank gose to lube oil cooler where it is cooled by the engine cooling system. - Oil then passes to lube oil strainer where it is filtered once again. - The oil filter (Michiana oil filter) contain 5 paper type filter elements. - A bypass valve provided across the filter tank and set at 40 PSI. - If the filter is clogged and pressure difference reaches to 40 PSI, the bypass valve delivers lube oil directly to the cooler. - This ensures adequate lube oil supply to the engine avoiding damages to the moving parts. - The oil filter and the lube oil cooler are located in the equipment rake. - The lube oil strainer is having 02 fine mesh strainer elements. **2. Main lubricating oil system** - There is a suction pipe (coming from the lube oil strainer) for the piston cooling oil system and the main lube oil system. - The piston cooling oil system pump receives oil from a common suction pipe and delivers oil to the 2 piston cooling oil manifolds extending the full length of the engine, one on each bank. - A piston cooling oil pipe at each cylinder directs a stream of oil to cool the underside of the piston crown. - This stream of oil also lubricates the ring belt. - Some of this oil enters oil grooves in the piston pin bearing for lubrication. - Oil after cooling and lubrication drains back in to the oil sump. **3. Piston cooling oil system** - The main lubricating oil system supplies oil under pressure to most of the moving parts of the engine. - The main lube oil pump takes oil from the strainer housing through a common suction. - Oil from the pump goes to the main oil manifold, which is located above the crankshaft, extends to the length of the engine. - Maximum oil pressure in the system is control by a relief valve in the passage between the pump and the main oil manifold. - The pressure relief valve is set to 125PSI, which relives excess oil back to the sump. - Oil tubes in the center of the each main bearing receives oil from the main manifold to the upper half of the crankshaft main bearings. - Drilled passage in the crankshaft supplies oil to the connecting rod bearings, vibration damper and accessory drive gear at the front end of the crankshaft. - Oil from the manifold enters gear train at the rear end of the engine at the idler gear stub shaft. - Oil passes in the base of the stub shaft from where oil is distributed to various parts through passage. - One passage conducts oil to the left bank camshaft drive gear stub shaft bracket through a jumper. - Another passage conducts oil to the Right Bank camshaft drive stub shaft bracket and the turbo charger oil filter supply line. - Oil enters the hollow bore camshaft from the camshaft stub shafts. - Radial holes in the camshafts conducts oil to each camshaft bearing. - An oil line from each camshaft bearing at each cylinder supplies oil to the rocker arm shaft, rocker arm cam follower assemblies, hydraulic lash adjusters and to rocker arm. - Leaks of oil return to the sump. **The turbo charger oil filter supply line sands oil to the turbo lube oil filter which sands oil to the turbo oil manifold and then to turbo for cooling and lubrication.** - A branch line taken to the wood word governor low lube oil pressure shut down device and also to the hot oil detector. - The minimum oil pressure is approximately 8-12 PSI at idle and 25-29 PSI at full speed. - In the event of insufficient oil pressure, a shutdown feature in the governor will automatically protect the engine by shutting down. - The turbo charger oil filter provides additional protection for the high-speed bearing and other lubricated areas of the turbo. - The filter heads contains 2 check valves, one to prevent the lube oil from the soak back system from going into the turbo charger filter during soak back pump operation and the other to prevent lube oil from the turbo charger filter from entering the soak back system when the engine is running. - Passages in the turbo charger conducts oil to the turbo bearings, idler gear, planet gear assembly and auxiliary drive bore. **4. Soak Back or turbo lube system** - To ensure lubrication of the turbo charger prior to the engine start and the removal of residual heat from the turbo after engine shutdown, a separate lube oil pressure source is provided. - This pressure system is controlled automatically by the locomotive control system. - An electrically operated turbo soak back pump draws oil from the oil sump, feed the oil through a soak back filter and finally to the turbo. - A 70-PSI soak back filter bypass valve is provided inside the soak back filter housing to bypass filter whenever it clogs to protect Turbo-charger. - This soak back pump automatically starts working before cranking the engine. - When the engine start, the motor driven soak back pump is still running, main lube oil pressure from the engine driven pump becomes greater than the motor driven soak back pump pressure. - As there is no outlet for the lower pressure oil, the relief valve is provided in the filter head set to 32 PSI will return the oil back to engine sump. **Lube oil pumps** - Each system has its own lube oil pump. - The main lube oil pump, piston cooling oil pump and scavenging oil pumps are driven from the accessory gear train at the front end of the engine. - The soak back or turbo lube system is driven by a electric motor. - The main lube oil pump and piston cooling oil pump is a individual pump but both contained in one housing and driven from a common drive shaft. **Considerable heat will remain in the metal parts of the turbine when the engine is shut down and due to sudden cut off oil supply to the bearings, damage or more wear will take place in the bearings since the turbo rotor will be rotating even after the engine stops due to its momentum.** - To avoid the thermal stressing and unwanted wear in the bearings due to no oil supply, this soak back pump automatically start working after shutting down of the engine. - Soak back pump will be working for 30 to 35 minutes approximately even after engine shutdown. - This ultimately increases the life of the turbo. **Lube Oil Separator** - The oil separator is an elbow shaped cylindrical housing containing a wire mesh screen element. - It is mounted on turbo charger housing. - An elbow assembly connects the separator to the ejector tube assembly in the exhaust stack. - The eductor tube in the exhaust stack creates suction in the engine crankcase and draws up oil vapor from the engine crankcase, while doing so. - The oil drawn will be collected on the wire mesh element and drain back to he engine sump. **Hot Oil Detector** - Normally there is a close relationship between engine coolant temperature and engine lube oil temperature. - Hot oil detector senses the oil temperature and send informations to EM2000. - If the temperature of the oil exceeds approximately 255 degree F (124 degree C) EM 2000 will shut down the engine through governor and the fault will be displayed on the EM2000 screen. ### 2.4 Air Intake System **Air intake system consists of the following components:** - Turbo charger, - Inertial air intake filters, - Baggie type fibre glass air intake filters, - After cooler **Turbo Charger:** - The primary use of the turbo charger is to increase air supply to engine to produce more horsepower and provide better fuel efficiency by the utilization of exhaust gases. - The turbo charger has a single stage turbine with a connecting gear train. - The connecting gear train work in the condition of engine starting/ light load operation and rapid acceleration. - When the engine work on full load (approximately in 6th notch) the energy of the exhaust gases is sufficient to drive the turbo charger and the turbine rotor rotates without any mechanical help from the engine. - At this point, an overriding clutch in the drive gear train disengages and the turbo charger drive is disconnected from the engine gear train. **The rotor shaft assembly of turbo is divided into 3 parts:** - Sun-gear shaft: -When engine is starting or it works on slow speeds or lower notch operations, the sun-gear shaft receive drive from the engine through the planet gear system and a clutch. - Exhaust gas driven turbine: - The burnt exhaust gases are directed to passage through a fixed nozzle ring between exhaust manifold and turbine. - The exhaust gases is directed by the fixed nozzle ring on to the turbine wheel blades and the heat energy is converted into mechanical rotary motion. - The diffuser is another aerodynamic device located in the turbine section of the turbo. - The diffuser is basically an arrangement of 3 to 4 vanes, which are placed behind the turbine blades these provide a smooth transition path for the gas to flow, thereby eliminating turbulence. - Then exhaust gases are expelled out through exhaust duct. - A built-in aspirator tube provided in exhaust ducts contains an "eductor tube" which provide suction in the engine crank case and maintains vacuum in the engine crankcase. - Impeller with diffuser: - On the other end of the rotor assembly, an impeller (compressor) with a diffuser ring is provided. - The impeller induces a partial vacuum in the air inlet casing. - The impeller inducer draws air from the clean air room where the clean air available after passing through cyclonic air inlet filter and secondary through a baggy type fiber glass secondary filter. - The air drawn by the blower is compressed in the blower causing and presses through a compressor diffuser directs the flow of compressed air to provide a smooth air delivery which is free from turbulence. **Inertial Air Intake Filter** - The inertial air inlet filters are cyclonic types consisting of many filter tubes mounted in a single assembly. - The reduction in pressure in the clean air compartment causes the outside air to rush through the filters to fill the depression. - As the air passes through the filter tubes and stationary vanes in the intake throats imparts a spinning motion to the air. - By spinning motion dirt particles are thrown to the outer wall of the tube by a centrifugal force. - These particles are carried to the bleeds duct (dustbin), where they are removed by dustbin blower and thrown out from the locomotive. - The resulting clean air enters in the air compartment. - In addition to clean the filters, the dust bin blower increases their efficiency by increasing the velocity of the air passing from the filter tubes **Baggie Type Air Intake Filter** - The diesel engine requires fine clean air for combustion of the fuel. - The inertial air filters approach 90% efficiency on throttle 8th but it is not adequate to the engine. - A secondary engine air filters are provides to filter the reminder contaminants. - These filters are oil coated and made by fiberglass material. - This material is very efficient in filtration. **Aftercooler** - A four-passage aftercooler is providing on the engines. - Which cools the compressed air before entering the air box by its efficient heat exchange capacity. - Thus, the density of the air also increases and high density fresh, clean and compressed air is available for combustion of the fuel. ### 2.5 Compressed Air System - Compressed air in GM locomotive is used for the locomotive brake system as well as for auxiliary systems such as sanders, bell, horn, windshield wipers, rail lube systems, and radar head air cleaner. - The GM locomotive uses WLNA9BB model three-cylinder air compressor which is a two stage (low-pressure and high-pressure) compressor. - The compressor is water-cooled. - The compressor is mechanically driven by a driveshaft from the front or accessory end of the locomotive engine. - This driveshaft is equipped with flexible couplings to couple the compressor. - The compressor is equipped with three cylinders, two low pressures and one (in the center) high pressure. - Air is sucked through two dry pamic type air filters and compressed by the two low pressure cylinders. - After that the low-pressure compressed air passed through an intercooler. - The intercooler reduced the compressed air temperatures. - A pressure relief valve is provided on the intercooler for intercooler safety. - After this the compressed air moves on to the high-pressure cylinder where it is again compressed to main reservoir pressure. - Between the compressor and main reservoir an aftercooler cooling coil is provided to reduce the air temperature. - The compressor has its' own internal oil pump and pressure lubricating system with an oil filter. - The oil level is checked during running by means of the dipstick mounted on the side of the compressor crankcase. - When adding oil in the compressor it must be in stop position. - At idle speed and normal operating temperature, the oil pressure should be between 18-25 psi. - A plugged opening is provided for installation of an oil pressure gauge. **COMPUTER CONTROLLED BRAKE SYSTEM (CCB)** - The loco is equipped with a KNORR brake system. - The KNORR system is computer-controlled air brake system (CCB). - The CCB equipment is a complete microprocessor-based air brake control system. - All logics are computer controlled. - The driver uses one of the two control stands (cab control unit (CCU) to control the CCB system. - Emergency applications are also initiated pneumatically in parallel with computer initiated emergency applications. ### 2.6 Electrical System - Power Distribution system in GT46MAC locomotives the diesel engine is the source of locomotive power, when the engine is running it directly drives three electrical generators: - Main generator (traction alternator) - Companion alternator - Auxiliary generator **Main generator (traction alternator)** - The main generator (traction alternator) rotates at engine speed generating AC power. - Rectifiers are covered within the generator assembly. - The rectifiers convert the AC power to DC, and the DC output is applied to DC link. - Switch gear and contractors supply DC voltage to traction inverter circuits. - The traction inverters convert the DC link voltage to 3- phase AC power for the traction motors. - There are two separate computers TCC1 and TCC2 which control the traction motors by varying the voltage and frequency which is fed to traction motors to get the proper torque and speed i.e., the output from traction motors. **Companion alternator** - The companion alternator is directly coupled to the traction alternator and is within the main generator assembly itself. - Output is utilized for the following: - To excite the main generator (traction alternator) field. - To drive the two rectifier cooling fan motors. - To drive the inertial blower motors. - To drive the traction inverter blowers. - Various transducers and control devices. **Auxiliary generator** - The auxiliary generator is driven by engine gear train. - The output of aux. Gen. is converted to74V DC in a rectifier &output from the rectifier is utilized for the following: - To excite the companion alternator fields. - Control systems. - Battery charging. - F. P. Motor. - Turbo charger soak-back pump. - Lighting and Misc. equipment. ## 3 Diesel Traction ### 3.1 Diesel Traction - By the end of the 1960s, diesel had almost completely superseded steam as the standard railroad motive power on nonelectrified lines around the world. - The change came first and most quickly in North America, where, during the 25 years 1935-60 (and especially in the period 1951-60), railroads in the United States completely replaced their steam locomotives. - What caused the diesel to supersede the steam locomotive so rapidly was the pressure of competition from other modes of transport and the continuing rise in wage costs, which forced the railroads to improve their services and adopt every possible measure to increase operating efficiency. - Compared with steam, the diesel traction unit had a number of major advantages: - It could operate for long periods with no lost time for maintenance. - In North America the diesel could operate through on a run of 3,200 km (2,000 miles) or more and then, after servicing, start the return trip. - Steam locomotives required extensive servicing after only a few hours' operation. - It used less fuel energy than a steam locomotive, for its thermal efficiency was about four times as great. - It could accelerate a train more rapidly and operate at higher sustained speeds with less damage to the track. - In addition, the diesel was superior to the steam locomotive because of its smoother acceleration, greater cleanliness, standardized repair parts, and operating flexibility (a number of diesel units could be combined and run by one operator under multiple-unit control). - The diesel-electric locomotive is, essentially, an electric locomotive that carries its own power plant. - It brings to a railroad some of the advantages of electrification, but without the capital cost of the power distribution and feed-wire system. - As compared with an electric locomotive, however, the diesel-electric has an important drawback: since its output is essentially limited to that of its diesel engine, it can develop less horsepower per locomotive unit. - Because high horsepower is required for high-speed operation, the diesel is, therefore, less desirable than the electric for high-speed passenger services and very fast freight operations. ### 3.2 Diesel Development - Experiments with diesel-engine locomotives and railcars began almost as soon as the diesel engine was patented by the German engineer Rudolf Diesel in 1892. - Attempts at building practical locomotives and railcars (for branch-line passenger runs) continued through the 1920s. - The first successful diesel switch engine went into service in 1925. - "Road" locomotives were delivered to the Canadian National and New York Central railroads in 1928. - The first really striking results with diesel traction were obtained in Germany in 1933. - There, the Fliegende Hamburger, a two-car, streamlined, diesel-electric train, with two 400-horsepower engines, began running between Berlin and Hamburg on a schedule that averaged 124 km (77 miles) per hour. - By 1939 most of Germany's principal cities were interconnected by trains of this kind, scheduled to run at average speeds up to 134.1 km (83.3 miles) per hour between stops. - The next step was to build a separate diesel-electric locomotive unit that could haul any train. - In 1935 one such unit was delivered to the Baltimore and Ohio and two to the Santa Fe Railway Company. - These were passenger units; the first road freight locomotive, a four-unit, 5,400-horsepower Electro-Motive Division, General Motors Corporation demonstrator, was not built until 1939. - By the end of World War II, the diesel locomotive had become a proven, standardized type of motive power, and it rapidly began to supersede the steam locomotive in North America. - In the United States a fleet of 27,000 diesel locomotives proved fully capable of performing more transportation work than the 40,000 steam locomotives they replaced. - After World War II, the use of diesel traction greatly increased throughout the world, though the pace of conversion was generally slower than in the United States. ### 3.3 Elements of Diesel Locomotive - Although the diesel engine has been vastly improved in power and performance, the basic principles remain the same: drawing air into the cylinder, compressing it so that its temperature is raised, and then injecting a small quantity of oil into the cylinder. - The oil ignites without a spark because of the high temperature. - The diesel engine may operate on the two-stroke or four-stroke cycle. - Rated operating speeds vary from 350 to 2,000 revolutions per minute, and rated output may be from 10 to 4,000 horsepower. - Railroads in the United States use engines in the 1,000-revolutions-per-minute range. - In Europe and elsewhere, some manufacturers have favored more compact engines of 1,500-2,000 revolutions per minute. - Most yard-switching and short-haul locomotives are equipped with diesel engines ranging from 600 to 1,800 horsepower. - Road units commonly have engines ranging from 2,000 to 4,000 horsepower. - Most builders use V-type engines, although in-line types are used on smaller locomotives and for underfloor fitment on railcars and multiple-unit train-sets. - The most commonly employed method of power transmission is electric