DIESEL ELECTRIC TRACTION • This method of Traction is economically adopted in areas where the cost of diesel oil is low.(U.S.A). • This system is also adopted in areas where coal for steam traction is not available in plenty and water is sometimes scarce. • Diesel Electric Traction system employs a self – contained motive power unit using diesel engine which drives DC Generator. • This supplies current to the traction motors which are geared to driving axles. • The efficiency of diesel electric locomotive (26 to 30%) is more than that of steam locomotive(5 to 7%) and less than that of electric locomotive(34 to 38%).
TYPES OF DIESEL ELECTRIC LOCOMOTIVES • The main line diesel electric locomotive having engines of output not exceeding 1500 kW and speeds 160 km/h. • The shunting diesel electric locomotive having an engine of 225 to 375kW output and speed between 25 to 50 km/h. • The diesel electric multiple unit stock of which each motor has an engine of 135 to 150 kW output and train is capable of having speeds between 80 to 110 km/h. • The diesel electric rail car having an engine of 75 to 450kW output which may operate as a single car or with one or more trailer coaches.
DIESEL ELECTRIC LOCOMOTIVES • The diesel engine employed for diesel electric locomotives is usually high speed type with three or four different running speeds with different output power. • The generator maybe self excited type or separately excited type. • Diesel Electric Locomotive is the most versatile power unit.
DISADVANTAGES • Diesel Electric Locomotive is very expensive in the initial cost. • Life of diesel engine is low. • Locomotive requires cooling of engine in addition to motors and generators. • Regenerative Braking cannot be employed with diesel electric traction but rheostatic braking can be employed.
CHARACTERISTICS OF DIESEL ENGINE • Its Torque is fairly constant for various speeds and HP increases fairly uniformly with speed. • It has a small overload capacity of only 10%. • For Traction work, Torque is inversely proportional to speed and therefore and therefore constant torque of the diesel engine has to be modified to suit traction requirement by the use of a suitable torque converter.
- Fall '14
- H N SHANKAR