[A350XWB]

Originally Posted by binaiks

I am no expert in this, but this is done perhaps to improve efficiency. The ones having clutch-gear stuff (the hydraulic ones) are poor on efficiency - may be thats the reason.

Efficiency is one reason and the other reason is the difficulty to find a clutch strong enough to transfer the torque efficiently without frying it. For a train, the initial tractive effort required is so huge that ordinary clutch arrangements will fail even before the train starts to move (remember that clutch is a friction device). Fluid coupling is used for shunters, but there also, the power loss is huge.

Originally Posted by rajeshsundaram

Totally stupid wish.. but, wish TBHP reviews this engine too!

I hope that I will get a hands on, on the new loco.
I'm currently working on the WDP/G-4 class of locomotives and with some luck, I will be involved in the new loco project also.

OT: GTO, did you take the picture during the railway exhibition in Delhi? If yes, I was also supposed to be there to showcase some developments, but missed the event due to a slipped disc.

[rajeshsundaram]

Originally Posted by A350XWB

I hope that I will get a hands on, on the new loco.
I'm currently working on the WDP/G-4 class of locomotives and with some luck, I will be involved in the new loco project also.

Now I am sure you will make it happen. woww! :-)

[A350XWB]

Originally Posted by rajeshsundaram

Now I am sure you will make it happen. woww! :-)

Thanks a lot for the wish buddy. Have been out of action for some weeks due to health reasons.
Three weeks back, I was at KJM and had a full day with a WDG3C and a WDP4B. Sorry, no pictures as I didn't have my camera with me. But it was a real cool experience spending time with those huge machines

[RGK]

Wealth of information about Indian locos in this thread. Thanks all for sharing.

Read long back that when the loco is braked the electrical energy is transferred back to the grid without any loss. Is this true?

India has to construct more tracks (over coming land acquisition problems) with high speed capabilities like China. India should learn from US to construct freeways and from Europe to build high speed railways.

[ampere]

Originally Posted by RGK

Wealth of information about Indian locos in this thread. Thanks all for sharing.

Read long back that when the loco is braked the electrical energy is transferred back to the grid without any loss. Is this true?

That is called Regenerative Braking.

Regenerative brake - Wikipedia, the free encyclopedia

[mtnrajdeep]

Originally Posted by ampere

- For Diesel engines, you generate a 3Phase from the primary diesel generator. This is again converted to DC and inverted it back to polyphase AC.
This polyphase AC you can manipulate, without changing the basic parameters of the diesel generator of diesel loco. (Just as the case in electric locomotives).

Another point for making the diesel engine run as a generator is because then the engine can be run in it's most efficient rpm range without any link to the speed at which the train/locomotive is running at.

[ampere]

Originally Posted by mtnrajdeep

Another point for making the diesel engine run as a generator is because then the engine can be run in it's most efficient rpm range without any link to the speed at which the train/locomotive is running at.

Exactly. We all marvel at the improvements in semiconductors technology providing us faster CPUs.
But equally amazing development in the field of power electronics has also come about.
Deployment of new solid-state devices for high power applications has transformed fields like railway traction for ever.

[Blue Thunder]

Originally Posted by sen2009

...Its a diesel engine...

Firstly, it is not a diesel engine, it is a diesel-electric locomotive(there are diesel-hydraulic locomotives as well).

The diesel engine, in a diesel-fuelled-locomotive, drives an electric generator; the current produced by the generator is suitably modified (amplified/stepped-up) to power the electric motors, which then drive the wheels.

Originally Posted by sen2009

... so it should run like other diesel engines (in cars etc) with clutch-gear concept....

I dont know how to explain this : but in a nutshell, you would need a really huge engine to pull even a small 5-coach passenger train (for eg), if it were based on a diesel engine driving the wheels directly thru clutch/gear transmission. Also, the fuel efficieny would make it totally economically unviable.

Originally Posted by mtnrajdeep

Another point for making the diesel engine run as a generator is because then the engine can be run in it's most efficient rpm range without any link to the speed at which the train/locomotive is running at.

I would say that is a by-product and not the main reason !

[anky]

I live opp chinchpokili stn central railway mumbai from birth and can see the trains from my house everyday . Can someone tell me how disel electric engines are started . Can a battery start such a large engine . How is it done ?

[ampere]

Originally Posted by anky

I live opp chinchpokili stn central railway mumbai from birth and can see the trains from my house everyday . Can someone tell me how disel electric engines are started . Can a battery start such a large engine . How is it done ?

Theoretically if you ask, the diesel generators always keep running.
So 3-Phase supply is always available for the AC traction drive system.

Its just a question of engaging the series traction (first in line due to its capability to deliver a high starting toque)

But what is the sequence to start from a locomotive operation point of view, you need to look at IRFCA.

I did not understand your reference to the battery part. If you are equating it to a diesel automobile like thing, where we start from battery, then that comparison is not correct.

[sen2009]

Originally Posted by Blue Thunder

Firstly, it is not a diesel engine, it is a diesel-electric locomotive(there are diesel-hydraulic locomotives as well).

The diesel engine, in a diesel-fuelled-locomotive, drives an electric generator; the current produced by the generator is suitably modified (amplified/stepped-up) to power the electric motors, which then drive the wheels.

I dont know how to explain this : but in a nutshell, you would need a really huge engine to pull even a small 5-coach passenger train (for eg), if it were based on a diesel engine driving the wheels directly thru clutch/gear transmission. Also, the fuel efficieny would make it totally economically unviable.

I would say that is a by-product and not the main reason !

This is the most clear and lucid explanation. Thanks a lot.
So, the Diesel generator is supplying the electric motors and then electric motors are turning the wheel.

The obvious query is, why don't we do this in automobiles then? The efficiency factor must play there as well.

One more question - Somewhere I read that a diesel (or petrol) motor cannot deliver any torque at zero RPM, hence one has to slip clutch to get off from start. But an electric motor can deliver any amount of torque (within its ratings) at zero RPM. So, probably this may help the locomotives to get rolling with a huge load.

Is this a reason as well?

[Blue Thunder]

Originally Posted by anky

... Can someone tell me how disel electric engines are started . ...

There is a battery and starter-motor arrangement just like in automobiles. But it is not a simple key start like in automobiles; there is a sequence of steps that need to be followed, check-points to be followed/verified, before the starter motor is engaged and the diesel engine starts running.

And yes, the diesel locomotives are shut down/switched off, when not in use for longer durations.

Originally Posted by sen2009

...The obvious query is, why don't we do this in automobiles then? ...

I used to think about this a lot, when (a long time ago) I came to know that it was a diesel-electric and not just diesel : why not use the same for cars, it would be so cheap to run a (diesel-hybrid) car. I think there is no simple answer to that question.

I think there are a lot of complex factors why the same has not happened in the automobile industry : investment inertia is probably a key factor (automobile companies have already invested a lot in the existing systems - manufacturing and research included).

[RGK]

Originally Posted by Blue Thunder

The diesel engine, in a diesel-fuelled-locomotive, drives an electric generator; the current produced by the generator is suitably modified (amplified/stepped-up) to power the electric motors, which then drive the wheels.
I dont know how to explain this : but in a nutshell, you would need a really huge engine to pull even a small 5-coach passenger train (for eg), if it were based on a diesel engine driving the wheels directly thru clutch/gear transmission.
I would say that is a by-product and not the main reason !

Till I read this post, I was thinking the diesel locomotive completely runs as a diesel engine (as seen in road transport). .
So it is a generator which produces electric current to pull the entire train whereas the electric loco gets the necessary power from the overhead high voltage cables.

Can someone explain how our (Delhi) Metro runs. Recently travelled in the airport express (awesome work by DMRCL).
In Singapore some metros are driverless. An engineer checks all the critical parameters in the first trip and leave. The train services the whole day without the driver. Which are the companies manufacturing Electric locos in India?

[trumpet]

Hi,

Starting a diesel loco is not as simple as an automobile. There is a sequence of steps to be followed, because you are dealing with a diesel generator coupled to an alternator.

This link provides details..
[IRFCA] Starting a WDP-2

[A350XWB]

Originally Posted by Blue Thunder

There is a battery and starter-motor arrangement just like in automobiles. But it is not a simple key start like in automobiles; there is a sequence of steps that need to be followed, check-points to be followed/verified, before the starter motor is engaged and the diesel engine starts running.

There is a small addition here. On the EMD locos, it is almost like an automobile start. Move the isolator switch to Starting position, keep the stater switch at the "prime" position for around 15s and then turn it to crank. This procedure can be used is the loco is still warm. If the loco is cool, (I forgot the exact time, I think it's 24 or 48 hours after the engine has been stopped) the priming has to be done by circulating oil from outside, using a pump.
The whining of the starter motor is so addictive and the vibrations from the 16 cylinder V-engine is surprisingly low.

On a diesel-electric locomotive also, dynamic braking is used, but the energy produced is dissipated using a forced air cooled resistive grid on the locomotive.