The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Page 1 of 2 1 2 >
Topic Options
Rate This Topic
#124010 - 06/26/06 04:34 AM Diesel-Electric Locomotives
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
Thanks to Alan Belson for the following. Images will take a while to load.....

 Quote:
Basic principles of Diesel-Electric Traction.

The diesel-electric locomotive is essentially an assembly of three well-known machines, as shown in Fig 46.

A diesel engine crankshaft rotates a generator armature. The current produced causes a traction motor to rotate and drive the wheels through a reducing gear set. Such a simple arrangement would not be satisfactory. Means must be provided to start the engine. It should also be possible to run the engine without running the vehicle. Reversing gear, a cooling system for oil and water is required and the generator will require regulation. Forced ventilation will be needed to keep the drive motor(s) and generator(s) compact, and arrangements for vacuum or pressure braking systems provided, as well as provision of auxiliary electric power supplies.

Fig 47 shows the diagrammatic arrangement of generator and motor windings.




The current for the electromagnetic field of the generator is supplied by a separate constant voltage supply, giving the basic diesel traction arrangement of a separately excited generator electrically connected to a series wound dc motor. This is shown schematically in Fig 48.




Fig 49 shows a main generator’s field windings supplied by an engine driven auxiliary generator via a load regulator, the latter’s field windings being supplied by a battery which it keeps charged by means of a charging regulator [not shown]. The main generator output feeds the traction motor. The load regulator is a variable resistance, which in practice is automatic, being under the control of the engine’s governor mechanism.

In Fig 50 is shown the addition of a ‘field diverting resistance’ in parallel with the motor’s field, which will weaken the motor field strength when introduced. This enables the motor’s traction characteristics to be varied.




Fig 51 shows arrangements to enable motor reversal, as field current flow reversal causes the motor armature to reverse rotate.

Fig 52 shows arrangements for starting the diesel engine. Battery current flowing through the main generator starting field and its armature causes the generator to function as a series wound motor. Battery capacity and the starting field-windings are arranged to provide sufficient torque to turn the engine over at sufficient rpm for starting. To prevent current flowing to the traction motors, their circuits are disconnected during the starting operation.

Fig 53 shows the battery charging arrangements.



Fig 54 shows the services connected to the respective main and auxiliary generators.




[This message has been edited by pauluk (edited 06-26-2006).]

Top
Tools for Electricians:
#124011 - 06/26/06 04:35 AM Re: Diesel-Electric Locomotives
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
 Quote:
Fig 55 shows a schematic practical diesel electric control arrangement.




The inherent characteristics of an engine driven generator and a series wound direct current traction motor are that when a generator runs at constant speed supplying a traction motor, any increase in current demand produces a voltage decrease, so that the power tends to remain constant. This contributes to the condition required whereby locomotive speed may vary while engine speed and output remain constant. An electrical arrangement which will take up the drive smoothly and which will give the required torque-conversion automatically is necessary. This is accomplished either by variation of engine speed or variation of the generator field excitation, resulting in conversion of engine horsepower to variable torque and speed at the driving wheels. Although maximum traction effort may be required to move a train from standstill, the required horsepower will be less than that needed to maintain maximum speed.

The torque exerted by a series wound dc traction motor is proportional to armature current and the magnetic circuit flux. At full engine output the ratio of flux from the maximum current to the maximum voltage conditions may be as high as 3:1 while the current to the motor may vary over a range of approximately 2:1. It is therefore feasible to an electric transmission to have a torque-conversion range of approximately 6:1 while full engine horsepower is applied.


The speed and traction performance of the locomotive is fixed by the available horsepower of the diesel engine, making due allowance for transmission losses and the power required for the auxiliary services.
This point is illustrated in Fig 56, where any point on the curve ‘ADBC’ gives substantially the same horsepower. In theory this curve could be extended indefinitely at both ends, but is limited at the top end ‘A’ by the top speed required in service and at the low end ‘B’ by traction adhesion between wheels and rails. In practice, with a given generator, the limiting features are the maximum field strength on one hand and the commutation at the high current end characteristic on the other.




The curve ‘ADBC’ shown in Fig 56 can be readily converted into a generator curve of constant electrical power, with current in place of speed and voltage in place of traction effort. This is shown in Fig 57 by the curve ‘ACB’. The type of generator normally used for this application would have an inherent characteristic shown in the curve ‘EADBG’, while the available horsepower, [expressed in volts and amps], would be shown by the curve ‘ACB’. The engine cannot cope with that portion, ‘ADB’ of the curve ‘EADBG’ but two ways of dealing with this difficulty are available. The generator characteristics can be designed so the curve ‘EADBG’ does not cut the curve ‘ACB’; but at best this will provide full engine horsepower at one point only. Alternatively, regulation mechanisms can be provided so that the portion ‘ADB’ of the curve is forced to approximate to ‘ACB’. In these conditions, full engine horsepower is available over the whole operating range. The traction motors give the necessary speed and tractive effort to correspond with the generator’s voltage and current range. The motor armatures are connected to the driving wheels by reduction gears. The shape of the locomotive-speed to tractive-effort characteristic is not affected by a change of gear ratio. The only effect of a ratio change is to move the performance range up or down the horsepower curve in Fig. 56.

While it is not possible to construct a constant power generator [or at least in wasn’t 50 years ago], it is possible to construct one which approximates this ideal. One way to do this is to incorporate self-exited shunt-windings, which, with a separately exited field, work additive to the main windings.




A schematic of such an arrangement is shown in Fig. 58. The self-excited shunt field ‘GSF’ is additive to the separately excited field ‘GF’. The curves ‘1,2,3,4’ represent the generator output at constant speed for different strengths of the field ‘GF’. Curve ‘5’ represents available horsepower. Field ‘S’ is the starting field for cranking the diesel engine, and the starting circuit is shown in heavy lines.

Alan









[This message has been edited by pauluk (edited 06-26-2006).]

Top
#124012 - 06/27/06 09:48 PM Re: Diesel-Electric Locomotives
Scott35 Offline

Broom Pusher and
Member

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
Thanks to Alan for the submissions, and to Paul, for posting everything!

These examples are great for passing on the basics of Diesel-Electric Locomotives.

One minor point:

The text describes starting of the Prime mover (Diesel Engine) via the Main Generator (by applying Power to the Main Genny, as to make it rotate).

This was done on a few "First Generation" Diesels - such as EMD's "E" Series and a few Models from General Electric and Alco, however, many of the "latter 1st Generations" by EMD - such as the infamous "F" Series (FTs, F3s and the well known F7s), along with the "Newbee GP" Series (GP-7, GP-9) had Starter Motors.

For 2nd Generation Locomotives in the General Motors / Electro-Motive Division line (GM / EMD), most - if not all, of the Yard Switchers (AKA "Yard Goats") still used the Main Genny as a Starter Motor.
No "Road / Switcher" units used the Main Genny as a Starter - all contained specific duty Starter Motors.

I am unsure if General Electric's 2nd Generation Yard Goats used Starter Motors or the Main Genny.

As for Alcos', there were no new Models produced by the mid 1970's, as they began Bankruptcy procedures by then (sad).

Glad to see the Railfans alive at ECN! Feels like Home again!

For those still kind of curious to the Diesel-Electric Locomotive priniple, it's simply a "Motor-Generator" set, sitting on top of a Frame, which has Electric Motors on the Axles; and these Axle mounted Motors are driven by the Motor-Generator set riding on the Frame.

Scott35
_________________________
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

Top
#124013 - 06/27/06 11:18 PM Re: Diesel-Electric Locomotives
Av-guy Offline
Member

Registered: 12/28/04
Posts: 22
Loc: Bangkok,Thailand
I' d reccomend this page for anyone who wants to know more about diesel-electric locos
http://www.rr-fallenflags.org/manual/manual.html

Top
#124014 - 06/28/06 07:42 AM Re: Diesel-Electric Locomotives
Alan Belson Offline
Member

Registered: 03/23/05
Posts: 1801
Loc: Mayenne N. France
Scott, the text is a precis, [ to cut out convoluted waffle, repetition and the blatently obvious ], of a section in an early 50's[?] English Electric 'internal use' booklet, from which I posted some pics in a previous thread. Apologies if this led to the conclusion that the main generator was always used as a starter-motor. Whether this arrangement continued on later British locos I don't know, but as Engineers are always looking over other Engineers' shoulders to steal better ideas.........

Alan
_________________________
Wood work but can't!

Top
#124015 - 06/28/06 07:52 AM Re: Diesel-Electric Locomotives
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
 Quote:
the text is a precis, [ to cut out convoluted waffle, repetition and the blatently obvious ], of a section in an early 50's[?] English Electric 'internal use' booklet,


My apologies for neglecting to mention that fact from Alan's e-mail.

Top
#124016 - 06/28/06 08:51 AM Re: Diesel-Electric Locomotives
Scott35 Offline

Broom Pusher and
Member

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
Alan (and Paul);

I am the one who should be apologizing here!

My post does look a bit harsh, however, that was not the intentions at all!

I should have used a much more concise approach to explain the Starter Motor vs. Main Generator stuff, as I am very happy that you (Alan) submitted the text + Pictures, and that you (Paul) uploaded these items and create this thread.

Again, I am very sorry if my post came off as arrogant or crude to anyone.

Scott35
_________________________
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

Top
#124017 - 06/29/06 03:08 PM Re: Diesel-Electric Locomotives
gideonr Offline
Member

Registered: 12/18/04
Posts: 152
Loc: Edinburgh, Scotland, UK
Excuse my ignorance, but haven't most of them been changed to alternators? The last one I had a wee tour of had, with lots of space freed up as the alternator was physically a lot smaller.

Top
#124018 - 06/29/06 07:39 PM Re: Diesel-Electric Locomotives
Scott35 Offline

Broom Pusher and
Member

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
gideonr:

 Quote:

haven't most of them been changed to alternators?


In many of the "Early to Mid Era 1st Generation" Locomotives, made by EMD and General Electric, the Prime Mover was driving a DC Generator.

Around the late 1960's - with production of the "Later End of the 1st Generation" Locomotives, the makers began selling Locomotives with 3 Phase AC Alternators as an option, and by the early 1970's, 3 Phase AC Alternators became standard equipment*¹.

On the EMD / General Motors side, production of Locomotives with the "567 Series" Prime Mover (Diesel Engine) were normally coupled to DC Generators.

As the "645 Series" Prime Movers took over in 1966, they started to be coupled to 3 Phase AC Alternators more and more.

By the time the "710 Series" Prime Movers took over, they were All*¹ coupled to 3 Phase AC Alternators.


EMD's Yard Switchers still came standard with DC Main Generators. These cover the Models' ranging from the early TR-6 "Cow And Calf", through the SW-8, SW-1200, SW-1500 and the MP-1500

BTW: The EMD Prime Movers have always been produced by General Motors. The first one was the "Winton Model 201-A", which had a Bore and Stroke of 8" x 10".

The Model 201-A was succeeded in late 1938 by the "567 Series", which is a 2 Stroke Prime Mover, with a Bore and Stroke of 8½" x 10"
(567 In³ per cylinder).

The 567 was succeeded in 1966 by the "645 Series", which is also a 2 Stroker, but with a Bore and Stroke of 9 1/16" x 10"
(645 In³ per cylinder).

Around 1984, the 645 was succeeded by the "710 Series", which was the last of the normal production 2 Stroke Diesel Prime Movers from GMDD / Detroit Diesel.
It's Bore and Stroke were 9 1/16" x 11"
(710 In³ per cylinder).

I believe the 710G might be a 4 Stroker, but not sure.
The newer Model Passenger Locomotive - the "F59PHI" has, what sounds like, a 4 Stroke "Main" Prime Mover, along with a 4 Stroke Auxiliary / HEP Prime Mover.
The F59PH and F59PHI use the 710G Series Prime Mover, for the "Main" Prime Mover.

To my knowledge of the newest Prime Movers being developed by GM / EMD, the "265 Series" is the current one.
This is a 4 Stroke Prime Mover with A Bore and Stroke of 10.4" x 11.8"
(1002 In³ per cylinder)

I kind of went off the topic regarding Main Gennys, with the Prime Mover stats, but I thought this might be of interest.

Let me know if anyone wants some information regarding Main Generators used by EMD or GE, or any other Locomotive related information

Scott35
_________________________
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

Top
#124019 - 06/29/06 09:51 PM Re: Diesel-Electric Locomotives
frenchelectrican Offline

Member

Registered: 02/06/03
Posts: 938
Loc: Wi/ Paris France { France for ...
Scott:

The 710 series EMD diesel engine is still two stroke unit and the 710G is the latest model and they improve some design to meet the emmision i think tier 1 or 2 i am not sure because it kinda like blur along the way.

most 710 series do have either electric starting motor useally two of them or air starter if in staionary units as for starting motors they are pretty instering hook up they hook up the starting motor in series to use the 72 volt battery system which the starter motor is rated for 36 volt each but older unit can use the 36 volt with 36 volt battery [ kinda rare ]and yes the 710 emd do have starter fuse along on it it is 800 amp at 72 volt so you get the idea how much juice to turn it over.

the Ge units genrally have electric starter motor and a hand full have air starter as well

my freind he work on railroad with new AC traction system and he really like alot and he say hard to stall the AC compared to the DC traction motors can do espcally on " drag " lines aka hevey coal trains typically about 10-15K tons loads :eek

i will ansnwer more question later


Merci , Marc
_________________________
Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)


Top
Page 1 of 2 1 2 >



ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals