Railway engines of different countries
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AC VS DC TRACTION LOCOMOTIVES
The AC (alternating current) Drive, also known as Variable Frequency Drive, has been the standard in industry for many years. While it has been used in locomotives for over two decades (especially in Europe), it has only been recently that the price of the drives has allowed them to be used in most of the new diesel-electric locomotives in the United States.
AC traction for locomotives is a major improvement over the old DC systems. The primary advantages of AC traction are adhesion levels up to 100% greater than DC and much higher reliability and reduced maintenance requirements of AC traction motors.
The tractive effort of a locomotive (whether AC or DC) is defined by the equations:
Tractive effort = Weight on drivers x Adhesion
Adhesion = Coefficient of friction x Locomotive adhesion variable
The friction coefficient between wheel and rail is usually in the range of .40 to .45 for relatively clean, dry rail in reasonable condition and is essentially the same for all locomotives. The locomotive adhesion variable represents the ability of the locomotive to convert the available friction into usable friction at the wheel rail interface. It varies dramatically from about .45 for old DC units to about .90 for modern AC units. This variable incorporates many factors including electrical design, control systems, truck type and wheel conditions.
First generation DC locomotives such as SW1200s, GP9s, SD40s, and GE center cabs typically have adhesion levels of 18% to 20%. More modern units with adhesion control such as SD60s and Dash 8s have adhesion levels of 25% to 27%. The newer AC traction units such as the SD80MAC and the C44AC are usually rated at 37% to 39% adhesion. Thus, the newer locomotives have about twice the adhesion of the older units and the Class I railroads are, in fact, typically replacing two older units with a single new AC unit.
There are three primary reasons that AC traction offers so much more adhesion. First, in a standard DC drive, if wheel slip occurs, there is a tendency for the traction motor to speed up and run away, even to the point of mechanical failure if the load is not quickly reduced. As the wheel slippage increases, the coefficient of friction also drops rapidly to a level of 0.10 or less, and because all the motors are connected together, the load to the entire locomotive must be reduced. Therefore, maximum adhesion is obtained by operating at a level with a comfortable margin of safety below the theoretical maximum. More modern DC systems incorporate a wheel slip control which senses the beginning of a slip and automatically modulates the power in order to retain control. This allows the locomotive to operate safely at a point closer to its theoretical maximum.
The AC system, however, operates in a very different fashion. The variable frequency drive creates a rotating magnetic field which spins about 1% faster than the motor is turning. Since the rotor cannot exceed the field speed, any wheel slip is minimal (less than 1%) and is quickly detected by the drive which instantly reduces load to the axle.
Next, the DC locomotive typically has a number of throttle settings with a set power level for each one. While this sytem is simple and effective, it does not produce a constant motor torque since power is the product of torque and speed. Therefore, the tractive effort varies significantly for each throttle setting depending on speed, making it impossible to obtain maximum adhesion.
The AC locomotive, however, can control to a specific motor torque level allowing the tractive effort to be essentially constant at the higher range of available adhesion. Ths fast acting wheel slip control can counteract any wheel slip so that the torque level can be set close to the upper limits.
The third way that AC traction provides improved adhesion is through weight transfer compensation. When a locomotive is pulling a load, weight tends to transfer from the front axle to the rear axle of each truck. At maximum tractive effort, the weight on the lead axle may be reduced by about 20%. Since the tractive effort is proportional to the weight on drivers, then in a DC system where the motors are fed from a common source, the tractive effort will be determined by the lightest axle. Thus, in effect, the equivalent locomotive weight is reduced by about 20%. With an AC system, however, the drive is able to compensate for the weight transfer. When the lead axle goes light, the AC drive system will reduce power to that axle and apply more power to the rear axle without incurring wheelspin.
The combination of eliminating wheel slip and compensating for weight transfer gives the AC traction system an adhesion of 37% to 39% versus the 18% to 20% of the older DC systems. Therefore, a locomotive with AC traction can provide the same tractive effort as a DC locomotive weighing twice as much or can give twice as much tractive effort for the same weight.
GE and EMD added AC traction to their mainline units and were then able to replace two older DC units with one new AC locomotive. Republic locomotive took a different approach and decided to make a lighter, less costly unit for industrial switching. The DC powered SW9/SW1200, produced in large quantities from 1951 to 1965 and used for heavy yard switching as well as branch line service, was taken as the performance standard. At 230,000 to 240,000 pounds these units are typically rated at about 40,000 pounds tractive effort continuous (somewhat higher intermittent but limited by traction motors and generators). The AC traction RX500 at 144,000 pounds and a conservative 35% adhesion level is rated at 50,400 pounds tractive effort continuous.
With AC traction, it is also important to consider braking. As with traction, braking is a function of weight on drivers. Therefore, when using standard friction braking (tread brakes) the braking capability of the locomotive (excluding train braking) is proportional to the locomotive weight. With AC traction, however, the braking can be much higher because the drive system in braking acts just like the drive does in traction thus eliminating wheel slip. The drive converts the motors to generating mode (dynamic braking) and the electricity produced is dissipated in the braking resistors. Thus the motors are slowing the locomotive without using the air brakes. Again, the adhesion levels are much higher so the locomotive can again be significantly lighter for the same amount of braking. The dynamic braking in AC traction locomotives also allows full braking down to zero speed, unlike DC dynamic braking.
All in all, the AC traction locomotive offers about twice the amount of adhesion as a DC unit. Therefore, a modern lightweight AC locomotive such as the RX500 can provide as much or more tractive effort than an old style DC unit like the SW1200 which weighs 60% more.
The AC (alternating current) Drive, also known as Variable Frequency Drive, has been the standard in industry for many years. While it has been used in locomotives for over two decades (especially in Europe), it has only been recently that the price of the drives has allowed them to be used in most of the new diesel-electric locomotives in the United States.
AC traction for locomotives is a major improvement over the old DC systems. The primary advantages of AC traction are adhesion levels up to 100% greater than DC and much higher reliability and reduced maintenance requirements of AC traction motors.
The tractive effort of a locomotive (whether AC or DC) is defined by the equations:
Tractive effort = Weight on drivers x Adhesion
Adhesion = Coefficient of friction x Locomotive adhesion variable
The friction coefficient between wheel and rail is usually in the range of .40 to .45 for relatively clean, dry rail in reasonable condition and is essentially the same for all locomotives. The locomotive adhesion variable represents the ability of the locomotive to convert the available friction into usable friction at the wheel rail interface. It varies dramatically from about .45 for old DC units to about .90 for modern AC units. This variable incorporates many factors including electrical design, control systems, truck type and wheel conditions.
First generation DC locomotives such as SW1200s, GP9s, SD40s, and GE center cabs typically have adhesion levels of 18% to 20%. More modern units with adhesion control such as SD60s and Dash 8s have adhesion levels of 25% to 27%. The newer AC traction units such as the SD80MAC and the C44AC are usually rated at 37% to 39% adhesion. Thus, the newer locomotives have about twice the adhesion of the older units and the Class I railroads are, in fact, typically replacing two older units with a single new AC unit.
There are three primary reasons that AC traction offers so much more adhesion. First, in a standard DC drive, if wheel slip occurs, there is a tendency for the traction motor to speed up and run away, even to the point of mechanical failure if the load is not quickly reduced. As the wheel slippage increases, the coefficient of friction also drops rapidly to a level of 0.10 or less, and because all the motors are connected together, the load to the entire locomotive must be reduced. Therefore, maximum adhesion is obtained by operating at a level with a comfortable margin of safety below the theoretical maximum. More modern DC systems incorporate a wheel slip control which senses the beginning of a slip and automatically modulates the power in order to retain control. This allows the locomotive to operate safely at a point closer to its theoretical maximum.
The AC system, however, operates in a very different fashion. The variable frequency drive creates a rotating magnetic field which spins about 1% faster than the motor is turning. Since the rotor cannot exceed the field speed, any wheel slip is minimal (less than 1%) and is quickly detected by the drive which instantly reduces load to the axle.
Next, the DC locomotive typically has a number of throttle settings with a set power level for each one. While this sytem is simple and effective, it does not produce a constant motor torque since power is the product of torque and speed. Therefore, the tractive effort varies significantly for each throttle setting depending on speed, making it impossible to obtain maximum adhesion.
The AC locomotive, however, can control to a specific motor torque level allowing the tractive effort to be essentially constant at the higher range of available adhesion. Ths fast acting wheel slip control can counteract any wheel slip so that the torque level can be set close to the upper limits.
The third way that AC traction provides improved adhesion is through weight transfer compensation. When a locomotive is pulling a load, weight tends to transfer from the front axle to the rear axle of each truck. At maximum tractive effort, the weight on the lead axle may be reduced by about 20%. Since the tractive effort is proportional to the weight on drivers, then in a DC system where the motors are fed from a common source, the tractive effort will be determined by the lightest axle. Thus, in effect, the equivalent locomotive weight is reduced by about 20%. With an AC system, however, the drive is able to compensate for the weight transfer. When the lead axle goes light, the AC drive system will reduce power to that axle and apply more power to the rear axle without incurring wheelspin.
The combination of eliminating wheel slip and compensating for weight transfer gives the AC traction system an adhesion of 37% to 39% versus the 18% to 20% of the older DC systems. Therefore, a locomotive with AC traction can provide the same tractive effort as a DC locomotive weighing twice as much or can give twice as much tractive effort for the same weight.
GE and EMD added AC traction to their mainline units and were then able to replace two older DC units with one new AC locomotive. Republic locomotive took a different approach and decided to make a lighter, less costly unit for industrial switching. The DC powered SW9/SW1200, produced in large quantities from 1951 to 1965 and used for heavy yard switching as well as branch line service, was taken as the performance standard. At 230,000 to 240,000 pounds these units are typically rated at about 40,000 pounds tractive effort continuous (somewhat higher intermittent but limited by traction motors and generators). The AC traction RX500 at 144,000 pounds and a conservative 35% adhesion level is rated at 50,400 pounds tractive effort continuous.
With AC traction, it is also important to consider braking. As with traction, braking is a function of weight on drivers. Therefore, when using standard friction braking (tread brakes) the braking capability of the locomotive (excluding train braking) is proportional to the locomotive weight. With AC traction, however, the braking can be much higher because the drive system in braking acts just like the drive does in traction thus eliminating wheel slip. The drive converts the motors to generating mode (dynamic braking) and the electricity produced is dissipated in the braking resistors. Thus the motors are slowing the locomotive without using the air brakes. Again, the adhesion levels are much higher so the locomotive can again be significantly lighter for the same amount of braking. The dynamic braking in AC traction locomotives also allows full braking down to zero speed, unlike DC dynamic braking.
All in all, the AC traction locomotive offers about twice the amount of adhesion as a DC unit. Therefore, a modern lightweight AC locomotive such as the RX500 can provide as much or more tractive effort than an old style DC unit like the SW1200 which weighs 60% more.
Burger Boy
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I think this thread should be moved to the general images forum.
LOCOMOTIVE PRODUCTION UNITS ACROSS THE GLOBE
1. Australia
Avteq - Melbourne
United Group Rail - Newcastle & Perth
EDI Rail - New South Wales
EDI Walkers - Queensland
2. Canada
Bombardier Transportation - Montreal
Railpower Technologies - Vancouver
3. China
China Northern Rail Corporation Limited (CNR)
CSR Corporation Limited (CSR)
CNR Beijing February 7th Locomotive Works
CNR Changchun Railway Vehicles
Changsha Heavy Machinery
CNR Dalian Locomotive and Rolling Stock Company
Qishuyan Locomotive and Rolling Stock Works
CSR Sifang Locomotive and Rolling Stock, Co.
CNR Tangshan Railway Vehicle
Taiyuan Locomotive and Rolling Stock Works
Xiangtan Electric Manufacturing Group Corporation Ltd
CSR Ziyang Locomotive Works
CSR Zhuzhou Electric Locomotive Company
Zhuzhou CSR Times Electric
4. France
Alstom
Société Alsacienne de Constructions Mécaniques
CFD
5. Germany
Adtranz
AEG
Siemens AG
Vossloh
Voith
Hanomag
Henschel
Krupp
Krauss-Maffei
6. India
Bharat Heavy Electricals Limited
Chittaranjan Locomotive Works
Diesel Locomotive Works (DLW)
Golden Rock Locomotive Workshops
Bharat Earth Movers Limited
SAN Locomotive & Engineering Co Ltd. Benglore
7. Pakistan
Locomotive factory , Risalpur
8. Iran
MLC (Mapna Locomotive Engineering and Manufacturing Company)
Wagon Pars
9. Italy
Ipe
Valente
Ansaldo Breda
10. Japan
Kawasaki Heavy Industries Rolling Stock Company
Hitachi, Ltd.
Mitsubishi Heavy Industries
Toshiba
11. Korea
Hyundai Rotem
12. Russia
CJSC Transmashholding
Novocherkassk Electric Locomotive Factory(NEVZ)
Bryanskiy Machine-building Plant
Kolomensky Zavod (KTZ)
BMZ
Sinara Group
Ludinovoteplovoz
Ekaterinburg Electric Locomotive Factory EERZ
Mytischy Subway Carriages Factory (Metrovagonmash)
Saint Petersburg Subway Carriages Factory
13. South Africa
Union Carriage and Wagon
DCD Dorbyl
Girdlestone steam
Transwerk
14. United Kingdom
Alan Keef Ltd (narrow-gauge diesel/steam locomotives, permanent way)
Clayton Equipment Company Ltd (diesel/electric/battery locomotives)
Brush Barclay
Brush Traction (diesel/electric locomotives)
Exmoor Steam Railway (narrow-gauge steam locomotives)
Hunslet Engine Company (diesel locomotives/narrow-gauge steam locomotives)
Cowans Sheldon
TMA Engineering
15. United States
Brookville Equipment Corporation
GE Transportation
Electro-Motive Diesel
Wiese
Wabtec
Colmar
Harsco Corporation
National Railway Equipment Company
Progress Rail Services Corporation
Motive Power & Equipment Solutions, Inc
1. Australia
Avteq - Melbourne
United Group Rail - Newcastle & Perth
EDI Rail - New South Wales
EDI Walkers - Queensland
2. Canada
Bombardier Transportation - Montreal
Railpower Technologies - Vancouver
3. China
China Northern Rail Corporation Limited (CNR)
CSR Corporation Limited (CSR)
CNR Beijing February 7th Locomotive Works
CNR Changchun Railway Vehicles
Changsha Heavy Machinery
CNR Dalian Locomotive and Rolling Stock Company
Qishuyan Locomotive and Rolling Stock Works
CSR Sifang Locomotive and Rolling Stock, Co.
CNR Tangshan Railway Vehicle
Taiyuan Locomotive and Rolling Stock Works
Xiangtan Electric Manufacturing Group Corporation Ltd
CSR Ziyang Locomotive Works
CSR Zhuzhou Electric Locomotive Company
Zhuzhou CSR Times Electric
4. France
Alstom
Société Alsacienne de Constructions Mécaniques
CFD
5. Germany
Adtranz
AEG
Siemens AG
Vossloh
Voith
Hanomag
Henschel
Krupp
Krauss-Maffei
6. India
Bharat Heavy Electricals Limited
Chittaranjan Locomotive Works
Diesel Locomotive Works (DLW)
Golden Rock Locomotive Workshops
Bharat Earth Movers Limited
SAN Locomotive & Engineering Co Ltd. Benglore
7. Pakistan
Locomotive factory , Risalpur
8. Iran
MLC (Mapna Locomotive Engineering and Manufacturing Company)
Wagon Pars
9. Italy
Ipe
Valente
Ansaldo Breda
10. Japan
Kawasaki Heavy Industries Rolling Stock Company
Hitachi, Ltd.
Mitsubishi Heavy Industries
Toshiba
11. Korea
Hyundai Rotem
12. Russia
CJSC Transmashholding
Novocherkassk Electric Locomotive Factory(NEVZ)
Bryanskiy Machine-building Plant
Kolomensky Zavod (KTZ)
BMZ
Sinara Group
Ludinovoteplovoz
Ekaterinburg Electric Locomotive Factory EERZ
Mytischy Subway Carriages Factory (Metrovagonmash)
Saint Petersburg Subway Carriages Factory
13. South Africa
Union Carriage and Wagon
DCD Dorbyl
Girdlestone steam
Transwerk
14. United Kingdom
Alan Keef Ltd (narrow-gauge diesel/steam locomotives, permanent way)
Clayton Equipment Company Ltd (diesel/electric/battery locomotives)
Brush Barclay
Brush Traction (diesel/electric locomotives)
Exmoor Steam Railway (narrow-gauge steam locomotives)
Hunslet Engine Company (diesel locomotives/narrow-gauge steam locomotives)
Cowans Sheldon
TMA Engineering
15. United States
Brookville Equipment Corporation
GE Transportation
Electro-Motive Diesel
Wiese
Wabtec
Colmar
Harsco Corporation
National Railway Equipment Company
Progress Rail Services Corporation
Motive Power & Equipment Solutions, Inc
MM_Haider
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WoW.. Buddy can you please provide some link.. i am sooooo happy to hear that..
kobiraaz
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Bangladesh Railway:
Looks Chinese
That looks better than first class
But seriously, I dread travelling by rail. I have had bad memories by travelling through BR. Travelling by air all the way for me...
i think these are the current ....
2 links are given
first for the korean deal:
Pakistan to buy Korean locomotives
for 150 loco deal:
Pakistan Railway to purchase 150 locomotives from US, China | editors-pick | weekly-updates
CardSharp
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Where is Spain? I heard that Obama was shopping around in Spain for a possible highspeed rail project.
here you for spain:
Vossloh Rail Vehicles
Talgo
CAF
La Maquinista Terrestre y Marítima
Babcock & Wilcock
Cía. Euskalduna
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