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Technical & Operating Comparison between WAP-7 & WDP-4 on Various Parameters and which one is Economical from every Aspect  
1 Answers
Feb 15 2016 (23:10)

Entry# 1924     
Technical & Operating Comparison between WAP-7 & WDP-4 on Various Parameters and which one is Economical from every Aspect

★★  Info Update
Feb 15 2016 (22:06)
Blog Post# 1739931-0     
Guest: 7fc2cb96   Added by: xxx  Feb 15 2016 (23:10)
*********WAP-7 VS WDP-4(Electric Speed star VS Diesel Speed star of IR) *******
Question: Operating WAP 7 and WDP4 , which one is more economical, considering cost of maintenance of Over Head Wire and other stuff ?
answer is given by Mr Vignesh Kumar
Ans: Since this question is very specific to two locomotives used in India, let's look into some of the important specifications of both the locos.
Let's look at WAP-7 first --My favorite ;)(Here "My favorite" means Favorite of Mr Vignesh Kumar who gives this Answer)
Gear Ratio: 72:20
Axle load: 20.5t
Power: 6,350 hp (4,740 kW)
Tractive Effort: 36.0t
Weight: 123 ton ((121 long tons; 136 short tons))
Maximum speed Test Speed: 160 km/h (99 mph)
Operational Maximum:140 km/h (87 mph)
Power output Maximum: 6,350 hp (4,735 kW)
Continuous: 6,000 hp (4,474 kW)
**** Some WAP-7 Figures are corrected as these are wrong in the Link Provided below from the Following Link:
click here
Now let's look at WDP4
Engine: GM-EMD 16-710
Transmission: Electric (AC - AC)
Power: 4000hp
Tractive Effort: 27.0t (264.8kN). Some sources say 27.5t (269.8kN)
Weight: 118t
Engine rpm: 950
Weight: 118t
Fuel tank capacity: 6000l
Max Speed: 160-180 km/hr but restricted to 110km/hr
Let's compare Electric Locomotive vs Diesel Locomotive Efficiency
According to O-Keating's The Electric Engine, the major advantage of the electric locomotive engine over diesel engine is that electric engine uses a rather simple and straightforward technology. The electric engine pulls power directly from the power grid and requires only a transformer and a regulator to bring down the power to acceptable levels. Diesel engines on the other hand uses diesel to produce energy, which is then transformed into electricity, and then again into kinetic energy, making them only around 40 percent efficient for the diesel consumed.
IRFCA's Diesel vs Electric debate however argue that the total cycle efficiency of electric engine from power plant to wheels of the engine is much less than the diesel loco.
Electric Locomotive v/s Diesel Locomotive Technology
Electric engines are lightweight, constituting only motors and wheel axles, and have almost no moving parts. Diesel engines on the other hand have a large number of moving parts such as pistons, valves, turbines, and chains. Electric engines are therefore easier to maintain whereas the moving parts of a diesel engine require constant maintenance.
The lightness of the electric engine contributes to lesser wear and tear of the tracks in comparison with the diesel engine. Diesel engines however are capable of 10 percent higher load hauling capability.
The following picture depicts the story for Electric (on the left) and diesel locomotives.
The energy loss for electric locomotives happen at the power station and in transmission and not in the loco itself. As power stations get more efficient these loss too will reduce, making electric more efficient.
Electric locomotives have regenerative braking which feeds back the power when the loco is braking, thus making them even more efficient.
Electric Locomotive v/s Diesel Locomotive Speed
These are the results of the trail runs conducted by Indian Railways.
Note: All trials conducted with a 24-coach 1430 tonne passenger rake
The WDP4 and WAP7 are highlighted in blue. A WAP7 can accelerate quicker than the WDP4. If the the WAP7 is operated on a 25KM route then it will be able to attain a max speed of 120-130km/hr, but it takes 25.66 Kms for the WDP5 to acheive a speed of 110km/hr, meaning on a 25km route it will be able to do a max of 70-80 before it has to slow down again.Electric engines do not produce much heat and noise, meaning that most of the energy produces converts into foreword motion. Diesel engines, on the other hand waste generate much heat and noise, diverting the energy away from forward motion.
Electric motors have the ability to produce as much torque as the power supplied. The primary disadvantage of the diesel locomotive engine is the amount of electricity the diesel engine generates limiting the power supply, making such engines incapable of attaining higher speeds.
The speed record for an electric locomotive engine is 320 mph, and for a diesel locomotive engine 148 mph.
Electric Locomotive v/s Diesel Locomotive Commercial Consideration
A major commercial consideration for railways to prefer electric locomotive engines to diesel locomotive engines is cost and availability of diesel. Diesel is an expensive non-renewable fuel source whereas electricity is a cheaper and infinite source of energy.
The major advantage of the diesel locomotive engine is its ability to work under all conditions and at all terrains, and the major disadvantage of the electric locomotive engine compared to the diesel locomotive engine is the requirement for power supply in the form of overhead electric lines. The capital cost of laying 5 to 6 kilometers of traction wires is equivalent to the cost of a new diesel locomotive. In addition to the cost and difficulties of installing overhead power lines and sub-stations to supply power, the possibility of disruption of train services is always a live concern for the following reasons:
power disruption
damage to the overhead lines or posts supporting the electric lines
The pantograph on top of the locomotive not making proper contact with the electric wires
If the cost of infrastructure needed to setup the overhead lines and sub stations are to be taken into consideration then electric trains are not as efficient as EMD ones.
Diesel locomotive is in fact an Electric Locomotive carrying its own powerhouse. While the earlier versions of the diesel locomotives were indeed inefficient, today’s modern diesel locomotives with Electric transmission have all the benefits of modern technology. For routes with less traffic density it is more efficient to use diesel, as the breakeven point is pretty high.
Source of this Info and attached images: click here
Attached Loco Images:
WAP7-GZB-30241 --- This beautifully repainted WAP7 of Ghaziabad ELS was framed by Sam at NDLS trip shed while it was taking afternoon nap on 11th July 2014.
Link: click here
Courtesy: Sam
WDP4-SGUJ-20003 --- The Siliguri king caught napping at Patna Jn. on east end of PF-2 by Sam on a wet morning of Oct 2013.
Link: click here
Courtesy: Sam
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