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#60990 - 01/14/06 10:07 AM Diesel Electric Trains.  
iwire  Offline
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
I know we have members here that are into trains so I figure the answer is among you.

When I see the diesel electric commuter trains Photo coming into the station they sound like the diesel is idling. When they leave they sound like they rev up.

When I think of a generator I imagine a constant speed to maintain a voltage.

So what is going on?

If the generator is ramped up and down how is the voltage maintained for the aux systems like electronics, lighting, HVAC etc.

Do they have more than one source of power?

Pleases fill me in. [Linked Image]

Bob Badger
Construction & Maintenance Electrician

Work Gear for Electricians and the Trades

#60991 - 01/14/06 11:00 AM Re: Diesel Electric Trains.  
Radar  Offline
Joined: Apr 2004
Posts: 349
Los Angeles, CA
Yea, I think they have big diesel generators for traction power and smaller generators for hotel loads (lighting, heating & AC, etc.).

I ride a diesel loco commuter train to work every day, and it has happened in the past that the auxiliary generator will break down but the train can still get underway. No lights or ventilation - but we're moving.


There are 10 types of people. Those who know binary, and those who don't.

#60992 - 01/14/06 12:01 PM Re: Diesel Electric Trains.  
Active 1  Offline
Joined: Feb 2003
Posts: 687
Grayslake IL, USA

#60993 - 01/14/06 12:49 PM Re: Diesel Electric Trains.  
e57  Offline
Joined: May 2003
Posts: 2,876
Outside of the more specific train related items on Active's links above.

Ever hear a generator engine sound change when a heavy load is applied, or changed dramaticaly? RPMs dont change much on generators with precise Hz/RPM fuel controls, but the sound changes due to the loading of the engine, and the fuel mixture to maintain that RPM. Sounds like its rev'ed up. More likely that the gate (choke) to the turbo charger is opened up more, introducing a high pitched whine. And exhuast compression is higher.

During proper maintanance of generators it's required to \"load bank\" the gennie to reduce "wet stacking" of the engine and exuast systems. When you do this, you control the load applied to the gennie stepping up to ~80% of rated load. (And run it hard for several hours) But as you step it up, you'll get a good feel for pitch change vs. load, but RPM's have not changed much. At no load it may sound like a high idle, at full load it sounds like a semi charging down the freeway. Or a train leaving the station....

[This message has been edited by e57 (edited 01-14-2006).]

Mark Heller
"Well - I oughta....." -Jackie Gleason

#60994 - 01/14/06 12:59 PM Re: Diesel Electric Trains.  
RODALCO  Offline
Joined: Dec 2005
Posts: 854
Titirangi, Akld, New Zealand
Thanks Active1 for that link.

That link explains it all.

Here in NewZealand on long distance trains, usually only 1 dieselelectric engine and 3 or 4 passenger wagons are used.

The DX loco is a 2750 HP machine which is used for traction only. The engine idles at stops and by increasing the revs of the diesel and excitation of the generator, power is available for the DC traction motors.

For AC power a 200 kVA generator is in the luggage car and provide power 230/400 volts @ 50 Hz for lights, heating, airco etc.

The diesel hydraulics we use in Auckland use per 2 wagon set, 2 diesel engines connected to voith hydraulic transmission for traction and have a diesel genset underhung under the trailing wagon (leading wagon) Also 230 / 400 Volts ( not sure how many kVA ).

The DC electrics in Wellington 1500 Vdc use DC motor gensets which take power from the OH catenary wire.

The product of rotation, excitation and flux produces electricty.

#60995 - 01/14/06 01:45 PM Re: Diesel Electric Trains.  
Rewired  Offline
Joined: Jan 2006
Posts: 558
Hamilton, Ontario, Canada
In regards to e57:
Ahh yes! A working Turbo Diesel.. Music to my ears!
I have been around the small one at the retirement home I wired when they load tested it.. no load it does sound like its "racing".. The cover at the top of the gennie stack just flaps open and closed. nothing special...
Apply load and lookout. [Linked Image]
Immediately you hear the engine tone change but it doesnt drop in speed, you also hear the turbo "spool up" right away.
From outside you see the stack cover nailed wide open and can hear the growl from within.. The whole contraption makes you think there is a jet-engine hiding behind the big ventilation grill in the wall.

This is only a "baby" @ 500KW I was told hahaha


#60996 - 01/14/06 01:56 PM Re: Diesel Electric Trains.  
e57  Offline
Joined: May 2003
Posts: 2,876
Many larger gennies of 1Mw or more often have a load bank built in. If not, load against another gennie of equal size in parralel, slightly out of sync.... Two big engines in fight!
If you do that, the power is not usable! as it is artificially a wierd freq....

[This message has been edited by e57 (edited 01-14-2006).]

Mark Heller
"Well - I oughta....." -Jackie Gleason

#60997 - 01/14/06 11:28 PM Re: Diesel Electric Trains.  
dereckbc  Offline
Joined: Oct 2003
Posts: 156
Tulsa, OK
Bob, I do not know much about the systems, but they use two engines. One for the traction motors, and another for everything else.

#60998 - 01/15/06 07:46 AM Re: Diesel Electric Trains.  
iwire  Offline
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Thanks gentlemen.

The links Tom provided where interesting.

It seems that there are different ways of obtaining the same result.

Still keep the info coming.

Thanks, Bob

Bob Badger
Construction & Maintenance Electrician

#60999 - 01/15/06 11:46 AM Re: Diesel Electric Trains.  
bigrockk  Offline
Joined: Jan 2003
Posts: 174
Middle of Canada
I used to work on freight locomotives (older dc traction types,) so I will see what I can recall about one type of locomotive, specifically the GM, SD40-2. Forgive me if there are some minor errors but it has been awhile.

The main "generator" (AR10) is actually two, three phase alternators. Two separate three-phase stator windings are wound onto one frame and these share one rotating field. The three phase stator windings are brought out of the alternator (right bank and left bank) and immediately terminate on diode banks to rectify the three-phase to D.C. The D.C. is feed to the traction motors through "reversers" and power contactors. Traction motors are connected in series/parallel at lower speeds and to counter the effects of back EMF, they are connected in full parallel at higher speeds.

The fields current for the "AR10" is feed from an SCR assembly that is controlled (in the most basic sense) from throttle position and feedback signals.

Bolted to the back of the AR10 alternator is another alternator referred to as the D14. This was used to supply power for cooling fans, blower motors control circuits etc. There was no control on this alternator so the higher the rpm of the diesel engine the higher the output from the alternator.

A completely separate three phase, self excited alternator that was feed directly to a rectifier bank was used to supply 74V D.C. for things such as battery charging, lighting,
heating, control etc.

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