Electric locomotive

British Rail Class 90 90021 in First ScotRail livery at Edinburgh Waverley

Deutsche Bahn DBAG Class 152 pulling a freight train

New Jersey Transit ALP-46 AC locomotive based on the DBAG Class 101

"Electric Trains" redirects here. For the 1995 Squeeze single, see Electric Trains (song).

An electric locomotive is a locomotive powered by electricity from overhead lines, a third rail or an on-board energy storage device (such as a chemical battery or fuel cell). Electrically propelled locomotives with on-board fuelled prime movers, such as diesel engines or gas turbines, are classed as diesel-electric or gas turbine electric locomotives because the electric generator/motor combination only serves as a power transmission system. Electricity is used to eliminate smoke and take advantage of the high efficiency of electric motors; however, the cost of railway electrification means that usually only heavily-used lines can be electrified.

Characteristics

One advantage of electrification is the lack of pollution from the locomotives themselves. Electrification also results in higher performance, lower maintenance costs and lower energy costs for electric locomotives.

Power plants, even if they burn fossil fuels, are far cleaner than mobile sources such as locomotive engines. Also the power for electric locomotives can come from clean and/or renewable sources, including geothermal power, hydroelectric power, nuclear power, solar power and wind turbines. Electric locomotives are also quiet compared to diesel locomotives since there is no engine and exhaust noise and less mechanical noise. The lack of reciprocating parts means that electric locomotives are easier on the track, reducing track maintenance.

Power plant capacity is far greater than what any individual locomotive uses, so electric locomotives can have a higher power output than diesel locomotives and they can produce even higher short-term surge power for fast acceleration. Electric locomotives are ideal for commuter rail service with frequent stops. They are used on high-speed lines, such as ICE in Germany, Acela in the US, Shinkansen in Japan, China Railway High-speed in China and TGV in France. Electric locomotives are also used on freight routes that have a consistently high traffic volume, or in areas with advanced rail networks.

Electric locomotives benefit from the high efficiency of electric motors, often above 90%. Additional efficiency can be gained from regenerative braking, which allows kinetic energy to be recovered during braking to put some power back on the line. Newer electric locomotives use AC motor-inverter drive systems that provide for regenerative braking.

The chief disadvantage of electrification is the cost for infrastructure (overhead power lines or electrified third rail, substations, control systems). Public policy in the US currently interferes with electrification—higher property taxes are imposed on privately owned rail facilities if they have electrification facilities. Also, US regulations on diesel locomotives are very weak compared to regulations on automobile emissions or power plant emissions.

In Europe and elsewhere, railway networks are considered part of the national transport infrastructure, just like roads, highways and waterways, and therefore are often financed by the state. Operators of the rolling stock pay fees according to rail use. This makes possible the large investments required for the technically and in the long-term also, economically advantageous electrification. Because railroad infrastructure is privately owned in the US, railroads are unwilling to make the necessary investments for electrification.

History

Electric locomotive of the Baltimore Belt Line, 1895. The steam locomotive was not detached for passage through the tunnel. The overhead conductor was a ∩ section bar at the highest point in the roof, so a flexible, flat pantograph was used

Alco-GE Prototype Class S-1, NYC & HR no. 6000 (DC)

File:Kando Kalman mozdony.jpg

AC locomotive in Valtellina (1898-1902). Power supply: 3-phase 15 Hz AC, 3000 V. Designed by Kálmán Kandó in Ganz Company, Hungary and supplied by Westinghouse.

A GE steeplecab electric locomotive. This example is fitted with trolley poles for service on an interurban railroad.

A Milwaukee Road class ES-2, an example of a larger steeplecab switcher for service on an electrified heavy-duty railroad

The first known electric locomotive was built by a Scotsman, Robert Davidson of Aberdeen in 1837 and was powered by galvanic cells ('batteries'). Davidson later built a larger locomotive named Galvani which was exhibited at the Royal Scottish Society of Arts Exhibition in 1841. It was tested on the Edinburgh and Glasgow Railway in September of the following year but the limited electric power available from batteries prevented its general use. The first electric passenger train was presented by Werner von Siemens at Berlin in 1879. The locomotive was driven by a 2.2 kW motor and the train, consisting of the locomotive and three cars, reached a maximum speed of 13 km/h. During four months, the train carried 90,000 passengers on a 300 metre long circular track. The electricity was supplied through a third, insulated rail situated between the tracks. A stationary dynamo nearby provided the electricity. The world's first electric tram line opened in Lichterfelde near Berlin, Germany, in 1881. It was built by Werner von Siemens (see Berlin Straßenbahn). In Britain, Volk's electric railway was opened in 1883 in Brighton (see Volk's Electric Railway). In the US, electric trolleys were pioneered in 1888 on the Richmond Union Passenger Railway, using equipment designed by Frank J. Sprague.

Much of the early development of electric locomotion was driven by the increasing use of tunnels, particularly in urban areas. Smoke from steam locomotives was noxious and municipalities were increasingly inclined to prohibit their use within their limits. Thus the first successful working, the City and South London Railway underground line in the UK, was prompted by a clause in its enabling act prohibiting use of steam power. This line opened in 1890, using electric locomotives built by Mather and Platt. Electricity quickly became the power supply of choice for subways, abetted by the Sprague's invention of multiple-unit train control in 1897. Surface and elevated rapid transit systems generally used steam until forced to convert by ordinance.

The first use of electrification on a mainline was on a four-mile stretch of the Baltimore Belt Line of the Baltimore and Ohio Railroad (B&O) in 1895. This track connected the main portion of the B&O to the newly built line to New York and it required a series of tunnels around the edges of Baltimore's downtown. Parallel tracks on the Pennsylvania Railroad had shown that coal smoke from steam locomotives would be a major operating issue, as well as a public nuisance. Three Bo+Bo units were initially used, at the south end of the electrified section; they coupled onto the entire train, locomotive and all and pulled it through the tunnels. Railroad entrances to New York City required similar tunnels and the smoke problems were more acute there. A collision in the Park Avenue tunnel in 1902 led the New York State legislature to outlaw the use of smoke-generating locomotives south of the Harlem River after 1 July 1908. In response, electric locomotives began operation in 1904 on the New York Central Railroad. In the 1930s, the Pennsylvania Railroad, which also had introduced electric locomotives because of the NYC regulation, electrified its entire territory east of Harrisburg, Pennsylvania.

Introduction of alternating current

The first practical AC electric locomotive was designed by Charles Brown, then working for Oerlikon, Zürich. In 1891, Brown had demonstrated long-distance power transmission, using three-phase AC, between a hydro-electric plant at Lauffen am Neckar and Frankfurt am Main West railway station, a distance of 280 km. Brown, using the experience he had gained while working for Jean Heilmann on steam-electric locomotive designs, had observed that three-phase motors had a higher power-to-weight ratio than DC motors and, because of the absence of a commutator, were simpler to manufacture and maintain. However, they were much larger than the DC motors of the time and could not be mounted in underfloor bogies: they could only be carried within locomotive bodies. In 1896, Oerlikon installed the first commercial example of the system on the Lugano Tramway. Three-phase motors, which run at constant speed and provide regenerative braking, are well suited to steeply graded routes and the first mainline three-phase locomotives were installed by Brown (by then in partnership with Walter Boveri) in 1899 on the Burgdorf—Thun line, Switzerland. Each thirty-tonne locomotive had two 150 h.p. motors. A development by Kálmán Kandó of the Ganz works, Budapest, working with Westinghouse of Italy, introduced an electro-mechanical converter, allowing the use of three-phase motors powered from single-phase alternating current, thus eliminating the need for two overhead conductor wires. The first implementation of industrial frequency single-phase AC supply for locomotives came from Oerlikon in 1901, using the designs of Hans Behn-Eschenburg and Emil Huber-Stockar; installation on the Seebach-Wettingen line of the Swiss Federal Railways was completed in 1904. The 15 kV, 50 Hz 345 kilowatts (460 hp), 48 tonne locomotives used transformers and rotary converters to power DC traction motors.

Italian railways were the first in the world to introduce electric traction for the entire length of a mainline rather than just a short stretch, using a system from Westinghouse, designed by Kálmán Kandó and a team from the Ganz works. The 106 km Valtellina line was opened on 4 September 1902. The electrical system was three-phase at 3 kV 15 Hz. The converter transformed single-phase current into three-phase alternating current within the locomotive. The voltage was significantly higher than used earlier and it required new designs for electric motors and switching devices. During the period of electrification of the Italian railways, some tests were made as to which type of power supply to use: in some sections there was a 3,600 V 16⅔ Hz three-phase power supply, in others there was 1,500 V DC, 3 kV DC and 10 kV AC 50Hz supply. During the 1930s, 3kV DC power was chosen for the entire Italian railway system. (Nowadays, 1,500 V DC is still used on some lines near France and 25kV 50Hz is used on high speed trains) Kandó designed a three phase AC traction in Evian Les Bains (Switzerland) in 1898.

In the United States, the Chicago, Milwaukee, St. Paul and Pacific Railroad (the Milwaukee Road), the last transcontinental line to be built, electrified its lines across the Rocky Mountains and to the Pacific Ocean starting in 1915. A few East Coast lines, notably the Virginian Railway and the Norfolk and Western Railway, found it expedient to electrify short sections of their mountain crossings. However, by this point, electrification in the United States was more associated with dense urban traffic and the centre of development shifted to Europe, where electrification was widespread.

A Swiss Re 420 leads a freight train down the South side of the Gotthard line, which was electrified in 1922. The masts and lines of the catenary can be seen.

In 1923, the first phase-converter locomotive in Hungary was constructed on the basis of Kandó’s designs and serial production began soon after. The first installation, at 50 Hz, 16 kV, was in 1932 on the 56 km section of the Hungarian State Railways between Budapest and Komárom. This proved successful and the electrification was extended to Hegyeshalom in 1934.

In Europe, electrification projects initially focused on mountainous regions for several reasons: coal supplies were difficult, hydroelectric power was readily available, and electric locomotives gave more traction on steeper lines. This was particularly applicable in Switzerland, where today close to 100% of lines are electrified. An important contribution to the wider adoption of AC traction came from SNCF of France after World War 2. The company had assessed the industrial-frequency AC line routed through the steep Höllental Valley, Germany, which was under French administration following the war. After trials, the company decided that the performance of AC locomotives was sufficiently developed to allow all its future installations, regardless of terrain, to be of this standard, with its associated cheaper and more efficient infrastructure. The SNCF decision, ignoring as it did the 2,000 miles (3,200 km) of high-voltage DC already installed on French routes, was influential in the standard selected for other countries in Europe.

The 1960s saw the electrification of many European main lines (Eastern Europe included). European electric locomotive's technology had improved steadily from the 1920s onwards. By comparison, the Milwaukee Road class EP-2 (1918) weighed 240 t, with a power of 3,330 kW and a maximum speed of 112 km/h; in 1935, German E 18 had a power of 2,800 kW, but weighed only 108 tons and had a maximum speed of 150 km/h. On 29 March 1955, French locomotive CC 7107 reached a speed of 331 km/h. In 1960 the SJ Class Dm 3 locomotives introduced on the Swedish Railways produced a record 7,200 kW. Locomotives capable of commercial passenger service at 200 km/h appeared in Germany and France in the same period. Further improvements resulted from the introduction of electronic control systems, which permitted the use of increasingly lighter and more powerful motors that could be fitted entirely inside the bogies (standardising from the 1990s onwards on asynchronous three-phase motors, fed through GTO-inverters).

In the United States, the use of electric locomotives declined in the face of dieselization. Diesels shared some of the electric locomotive’s advantages of over steam and the cost of building and maintaining the power supply infrastructure, which had always worked to discourage new installations, brought on the elimination of most mainline electrification outside the Northeast. Except for a few captive systems (e.g. the Black Mesa and Lake Powell), by 2000, electrification was confined to the Northeast Corridor and some commuter service; even there, freight service was handled by diesels.

In the 1980s, development of very high-speed service brought a revival of electrification. The Japanese Shinkansen and the French TGV were the first systems for which devoted high-speed lines were built from scratch. Similar programs were undertaken in Italy, Germany and Spain; in the United States the only new mainline service was an extension of electrification over the Northeast Corridor from New Haven, Connecticut to Boston, Massachusetts, though new light rail systems, using electrically powered cars, continued to be built.

On 2 September 2006, a standard production Siemens Electric locomotive of the Eurosprinter type ES64-U4 (ÖBB Class 1216) achieved a speed of 357 km/h, the record for a locomotive-hauled train, on the new line between Ingolstadt and Nuremberg.

Electric locomotive types

The operating controls of the 1 gauge cogwheel electric locomotive BDeh 4/4 view, operating in line Luzern-Engelberg. The wheel controls motor power, not driving direction.

Electric locomotive used in mining operations in Flin Flon, Manitoba. This locomotive is on display and not currently in service.

An electric locomotive can be supplied with power from

• Rechargeable energy storage systems, as battery or ultracapacitor-powered mining locomotives.
• A stationary source, such as a third rail or overhead wire.

This is in marked contrast to a diesel-electric locomotive, which combines an onboard diesel engine with an electrical power transmission or store (battery, ultracapacitor) system.

The distinguishing design features of electric locomotives are:

• The type of electrical power used, either alternating current or direct current.
• The method for store (batteries, ultracapacitors) or collecting (transmission) electrical power.
• The means used to mechanically couple the traction motors to the driving wheels (drivers).

Direct and alternating current

The most fundamental difference lies in the choice of direct (DC) or alternating current (AC). The earliest systems used direct current as, initially, alternating current was not well understood and insulation material for high voltage lines was not available. Direct current locomotives typically run at relatively low voltage (600 to 3,000 volts); the equipment is therefore relatively massive because the currents involved are large in order to transmit sufficient power. Power must be supplied at frequent intervals as the high currents result in large transmission system losses.

As alternating current motors were developed, they became the predominant type, particularly on longer routes. High voltages (tens of thousands of volts) are used because this allows the use of low currents; transmission losses are proportional to the square of the current (e.g. twice the current means four times the loss). Thus, high power can be conducted over long distances on lighter and cheaper wires. Transformers in the locomotives transform this power to a low voltage and high current for the motors. A similar high voltage, low current system could not be employed with direct current locomotives because there is no easy way to do the voltage/current transformation for DC so efficiently as achieved by AC transformers.

Italian freight locomotive E554 working with three-phase current. Note the two current collectors with separate heads for each phase. Picture taken in Liguria 1974.

AC traction seldom uses two-phase lines in place of single phase lines. The transmitted three-phase current drives induction motors, which do not have sensitive commutators and permit easy realisation of a regenerative brake. Speed is controlled by changing the number of pole pairs in the stator circuit and by switching additional resistors in the rotor circuit. The two-phase lines are heavy and complicated near switches, where the phases have to cross each other. The system was widely used in the northern part of Italy until 1976 and is still in use on some Swiss rack railways. The simple feasibility of a fail safe electric brake is an advantage of the system, while the speed control and the two-phase lines are problematic.

The Swedish Rc locomotive was the first series locomotive that used thyristors with DC engines.

Rectifier locomotives, which used AC power transmission and DC motors, were common, though DC commutators had problems both in starting and at low velocities. Today's advanced electric locomotives use brushless three-phase AC induction motors. These polyphase machines are powered from GTO-, IGCT- or IGBT-based inverters. The cost of electronic devices in a modern locomotive can be up to 50% of the total cost of the vehicle.

Electric traction allows the use of regenerative braking, in which the motors are used as brakes and become generators that transform the motion of the train into electrical power that is then fed back into the lines. This system is particularly advantageous in mountainous operations, as descending locomotives can produce a large portion of the power required for ascending trains.

Most systems have a characteristic voltage and, in the case of AC power, a system frequency. Many locomotives over the years were equipped to handle multiple voltages and frequencies as systems came to overlap or were upgraded. American FL9 locomotives were equipped to handle power from two different electrical systems and could also operate as conventional diesel-electrics.

While recently designed systems invariably operate on alternating current, many existing direct current systems are still in use – e.g. in South Africa and the United Kingdom (750 V and 1,500 V); Netherlands, Japan, Mumbai, Ireland (1,500 V); Slovenia, Belgium, Italy, Poland, Russia, Spain (3,000 V) and the cities of Washington DC (750 V).

Power transmission

A modern pantograph. The device shown is technically a half-pantograph.

See also: Railway electrification system

Electrical circuits require two connections (or for three phase AC, three connections). From the very beginning, the trackwork itself was used for one side of the circuit. Unlike model railroads, however, the trackwork normally supplies only one side, the other side(s) of the circuit being provided separately.

The original Baltimore and Ohio Railroad electrification used a sliding shoe in an overhead channel, a system quickly found to be unsatisfactory. It was replaced with a third rail system, in which a pickup (the "shoe") rode underneath or on top of a smaller rail parallel to the main track, somewhat above ground level. There were multiple pickups on both sides of the locomotive in order to accommodate the breaks in the third rail required by trackwork. This system is preferred in subways because of the close clearances it affords.

However, railways generally tend to prefer overhead lines, often called "catenaries" after the support system used to hold the wire parallel to the ground. Three collection methods are possible:

• Trolley pole: a long flexible pole, which engages the line with a wheel or shoe.
• Bow collector: a frame that holds a long collecting rod against the wire.
• Pantograph: a hinged frame that holds the collecting shoes against the wire in a fixed geometry.

Of the three, the pantograph method is best suited for high-speed operation. Some locomotives are equipped to use both overhead and third rail collection (e.g. British Rail Class 92).

Driving the wheels

One of the Milwaukee Road EP-2 "Bi-polar" electrics

During the initial development of railroad electrical propulsion, a number of drive systems were devised to couple the output of the traction motors to the wheels. Early locomotives used often jackshaft drives. In this arrangement, the traction motor is mounted within the body of the locomotive and drives the jackshaft through a set of gears. This system was employed because the first traction motors were too large and heavy to mount directly on the axles. Due to the number of mechanical parts involved, frequent maintenance was necessary. The jackshaft drive was abandoned for all but the smallest units when smaller and lighter motors were developed,

Several other systems were devised as the electric locomotive matured. The Buchli drive was a fully-spring loaded system, in which the weight of the driving motors was completely disconnected from the driving wheels. First used in electric locomotives from the 1920s, the Buchli drive was mainly used by the French SNCF and Swiss Federal Railways. The quill drive was also developed about this time and mounted the traction motor above or to the side of the axle and coupled to the axle through a reduction gear and a semi-flexible hollow shaft - the quill. The Pennsylvania Railroad GG1 locomotive used a quill drive. Again, as traction motors continued to shrink in size and weight, quill drives gradually fell out of favour.

Another drive example was the "bi-polar" system, in which the motor armature was the axle itself, the frame and field assembly of the motor being attached to the truck (bogie) in a fixed position. The motor had two field poles, which allowed a limited amount of vertical movement of the armature. This system was of limited value since the power output of each motor was limited. The EP-2 bi-polar electrics used by the Milwaukee Road compensated for this problem by using a large number of powered axles.

Modern electric locomotives, like their Diesel-electric counterparts, almost universally use axle-hung traction motors, with one motor for each powered axle. In this arrangement, one side of the motor housing is supported by plain bearings riding on a ground and polished journal that is integral to the axle. The other side of the housing has a tongue-shaped protuberance that engages a matching slot in the truck (bogie) bolster, its purpose being to act as a torque reaction device, as well as a support. Power transfer from motor to axle is effected by spur gearing, in which a pinion on the motor shaft engages a bull gear on the axle. Both gears are enclosed in a liquid-tight housing containing lubricating oil. The type of service in which the locomotive is used dictates the gear ratio employed. Numerically high ratios are commonly found on freight units, whereas numerically low ratios are typical of passenger engines.

Wheel arrangements

A GG1 electric locomotive

The Whyte notation system for classifying steam locomotives is not adequate for describing the varieties of electric locomotive arrangements, though the Pennsylvania Railroad applied classes to its electric locomotives as if they were steam or concatenations of such. For example, the PRR GG1 class indicates that it is arranged like two 4-6-0 class G locomotives that are coupled back-to-back.

In any case, the UIC classification system was typically used for electric locomotives, as it could handle the complex arrangements of powered and unpowered axles and could distinguish between coupled and uncoupled drive systems.

Electric traction around the world

Asia

Japan

The rail system of Japan consists of the following (as of 2005):

• 20,264 km (12,591 mi) of 1,067 mm (42.0 in) Cape gauge, of which 13,280 kilometres (8,250 mi) is electrified;
• 3,204 km (1,991 mi) of 1,435 mm (56.5 in) standard gauge, all electrified;
• 117 km (73 mi) of 1,372 mm (54.0 in) Scotch gauge, all electrified;
• 11 km (6.8 mi) of 762 mm (30.0 in) narrow gauge, all electrified.

Electrification systems used by the JR group, Japan's formerly state owned operaters, are 1,500V DC and 20kV AC for conventional lines and 25kV AC for Shinkansen. Electrification with 600V DC and 750V DC are also seen in private lines. The frequency of the AC power supply is 50 Hz in Eastern Japan and 60 Hz in Western Japan.

See also: List of railway electrification systems in Japan

Japan has come close to complete electrification largely due to the relatively short line distances and mountainous terrain which make electrical service a particularly economical investment. Additionally, the mix of freight to passenger service is weighted much more toward passenger service (even in rural areas) than in many other countries, and this has helped drive government investment into electrification of many remote lines.

Electrification began in earnest for local railways in the 1920s and main lines electrification began following World War II using a universal 1,500V DC standard and eventually, a 20kV standard for rapid intercity main lines (this is often overlaying 1,500V DC lines) and a 25kV AC standard for high-speed Shinkansen lines). Because most of the electrification infrastructure was destroyed in the war, the only variances to this standard with significant traffic are a few of the older subway lines in Tokyo and Osaka. The Tōkaidō Main Line, Japan's busiest line, completed electrification in 1956 and Tōkaidō Shinkansen was complete in 1964. By the mid 1970s, most main lines had been converted. During the 1970s and into the 1980s, when a fast growing Japanese economy encouraged massive infrastructure spending, almost every line with any significant traffic was electrified. Though the massive debts incurred for these upgrades (along with the more publicised expense of Shinkansen expansions) led to the privatization and break-up of the national rail company. By the time of the break up in 1987, electric service had penetrated to every line with significant traffic. In the 1990s, and 2000s, rural infrastructure was the focus of a lot of government stimulus funding and this included some rail electrification on infrequently used lines, as well as quite a lot of funding for further expanding the Shinken network (which, as with all high speed trains, is electric). The latter was mostly in the form of loans rather than direct investment as in the former.

Malaysia

Keretapi Tanah Melayu of Malaysia operated 25 kV AC electric multiple unit services, starting from their KTM Komuter in 1995. In December 2009, a fleet of new ETS are arrived.

Australia

Both Victorian Railways and New South Wales Government Railways, which pioneered electric traction in Australia in the early 20th century and continue to operate 1,500 V DC Electric Multiple Unit services, have withdrawn their fleets of main line electric locomotives.

In both states, the use of electric locomotives on principal interurban routes proved to be a qualified success. In Victoria, because only one major line (the Gippsland line) had been electrified, the economic advantages of electric traction were not fully realised due to the need to change locomotives for trains that extended beyond the range of the electrified network. VR's entire electric locomotive fleet was withdrawn from service by 1987 and the Gippsland line electrification was dismantled by 2004. Similarly, the new fleet of 86 class locomotives introduced to NSW in 1983 had a relatively short life as the costs of changing locomotives at the extremities of the electrified network, together with the higher charges levied for electricity use, saw diesel-electric locomotives make inroads into the electrified network and the electric locomotive fleet was progressively withdrawn. Electric power car trains are still used for urban passenger services.

Queensland Rail, conversely, implemented electrification relatively recently and utilises the more recent 25 kV AC technology with around 1,000 km of the QR narrow gauge network now electrified. It operates a fleet of electric locomotives to transport coal for export, the most recent of which are those of the 3,000 kW (4,020 HP) 3300/3400 Class. Queensland Rail is currently rebuilding its 3100 and 3200 class locos into the 3700 class, which use AC traction and only need three locomotives on a coal train rather than five. Queensland Rail is getting thirty 3800 class locomotives from Siemens in Munich, Germany, which will arrive during late 2008 to 2009. QRNational (Queensland Rail's Coal and Freight after separation) has increased the order of 3800 class locomotives from Germany. They continue to arrive late into 2010.

Europe

NER No.1, Locomotion museum, Shildon

Electrification is widespread in Europe. Due to higher density schedules, the operating costs of the locomotives are more dominant with respect to the infrastructure costs than in the US and electric locomotives have much lower operating costs than diesels. In addition, governments were motivated to electrify their railway networks due to coal shortages experienced during the First and Second World Wars.

It should also be noted that diesel locomotives have little power compared to electric locomotives, given the same weight and dimensions. For instance, the 2,200 kW of a modern British Rail Class 66 were already met in 1927 by the electric SBB-CFF-FFS Ae 4/7 (2,300 kW), which is even a bit lighter. However, for low speeds, tractive effort is more important than power. This is why diesel engines are competitive for slow freight traffic (as it is common in the US) but not for passenger or mixed passenger/freight traffic like on many European railway lines, especially where heavy freight trains must be run at comparatively high speeds (80 km/h or more).

These factors led to high degrees of electrification in most European countries. In some countries like Switzerland, even electric shunters are common and many private sidings can be served by electric locomotives. During World War 2, when materials to build new electric locomotives were not available, the Swiss Federal Railways installed electric heating elements, fed from the overhead supply, in the boilers of some steam shunters to deal with the shortage of imported coal.

The recent political developments in many European countries to enhance public transit have led to another boost for electric traction. High-speed trains like the TGV, ICE, AVE and Pendolino can only be run economically using electric traction and the operation of branch lines is usually less in deficit when using electric traction, due to cheaper and faster rolling stock and more passengers due to more frequent service and more comfort. In addition, gaps of un-electrified track are closed to avoid replacing electric locomotives by diesels for these sections. The necessary modernisation and electrification of these lines is possible due to financing of the railway infrastructure by the state.

India

In India, both AC and DC type of electrified train systems operate today. A 1,500 V DC-based train system is only operating in the Mumbai area. It is being converted to the 25 kV AC system. The rest of the India, where routes are electrified fully, operate under the 25 kV AC overhead wire. As of 2006, Indian railways haul 80% of freight and 85% of passenger traffic with electric locomotives.

Russia and former USSR

Soviet electric locomotive VL60^p_k (ВЛ60^п_к), c. 1960

Russia and other countries of the former USSR have a mix of 3,300 V DC and 25 kV AC electric railroads due to historical reasons.

The special "junction stations" (around 15 over the whole former USSR - Vladimir, Mariinsk near Krasnoyarsk etc.) were equipped with contact wiring switchable from DC to AC. Locomotive replacement is essential at these stations and is performed together with the contact wiring switching.

Most Soviet, Czech (USSR ordered the passenger electric locomotives to Czech Skoda factory), Russian and Ukrainian locomotives can only operate as DC or as AC. For instance, VL80 is an AC machine, with VL10 being something like a DC version of VL80. There were some half-experimental small-series like VL82, which could switch from AC to DC and were used in small amounts around the city of Kharkov in Ukraine. Also, the latest Russian passenger locomotive EP10 (experimental only?) is dual-system.

Historically, first the 3,300 V DC wiring was used due to vehicle simplicity. The first experimental track was in Georgian mountains, then the suburban zones of the largest cities were electrified for motor-car locomotive-less trains to be used - very advantageous due to much better dynamic of such a train compared to the steam one, which is important for the suburban service with frequent stops. Then the large mountain line between Ufa and Chelyabinsk was electrified.

For some time, electric railways were only considered to be suitable for suburban or mountain lines. In around 1950, a decision was made (according to the legend - by Joseph Stalin) to electrify the highly-loaded plain prairie line of Omsk-Novosibirsk. After this, electrifying the major railroads with 3,000 V DC became a mainstream.

25 kV AC contact wiring started in the USSR in around 1960, when the industry managed to build the rectifier-based AC-wire DC-motor locomotive (all Soviet and Czech AC locomotives were such; only the post-Soviet ones switched to electronically controlled induction motors). The first major line with AC power was Mariinsk-Krasnoyarsk-Tayshet-Zima; the lines in European Russia like Moscow-Rostov-on-Don followed.

In 1990s, some DC lines were rebuilt as AC ones to allow the usage of the huge 10 MWt AC locomotive of VL85. The line around Irkutsk is one of them. The DC locomotives freed by this rebuild were transferred to St. Petersburg region.

The Trans-Siberian Railway has been partly electrified since 1929 and entirely electric hauled since 2002. The system is 25 kV AC 50 Hz after the junction station of Mariinsk near Krasnoyarsk, 3,000 V DC before it and train weights are up to 6,000 tonnes.

United States

For most large systems, the cost of electrifying the whole system is impractical and generally only some divisions are electrified. In the United States, only certain dense urban areas and some mountainous areas were electrified and the latter have all been discontinued. The junction between electrified and non-electrified territory is the locale of engine changes; for example, Amtrak trains had extended stops in New Haven, Connecticut as diesel and electric locomotives were swapped, a delay which contributed to the electrification of the remaining segment of the Northeast Corridor in 2000.

In North America, the flexibility of diesel locomotives and the relative low cost of their infrastructure has led them to prevail except where legal or other operational constraints dictate the use of electricity. An example of the latter is the use of electric locomotives by Amtrak and commuter railroads in The Northeast.

Battery locomotive

A London Underground battery-electric locomotive at West Ham station

A battery locomotive (or battery-electric locomotive) is a type of electric locomotive powered by on-board batteries; a kind of battery electric vehicle. Such locomotives are used where a conventional diesel or electric locomotive would be unsuitable. An example of use is the hauling of maintenance trains on electrified lines when the electricity supply is turned off, such as by the London Underground battery-electric locomotives.

Another use for battery locomotives is in industrial facilities – as an alternative to the fireless locomotive – where a combustion-powered locomotive (i.e., steam- or diesel-powered) could cause a safety issue, due to the risks of fire, explosion or fumes in a confined space.

Kennecott Copper

In 1928, Kennecott Copper ordered four 700-series electric locomotives with on-board batteries. These locomotives weighed 85 tons and operated on 750-volt overhead trolley wire with considerable further range whilst running on batteries. The locomotives provided several decades of service using Nickel-iron battery (Edison) technology. The batteries were replaced with lead-acid batteries, and the locomotives were retired shortly afterward. All four locomotives were donated to museums, but one was scrapped. The others can be seen at the Boone and Scenic Valley Railroad, Iowa, and at the Western Railway Museum in Rio Vista, California.

See also

• Battery is our business

• Railway electrification system
• Hybrid train
• Air brake (rail)
• Railway brakes
• Boxcab
• Emily Davenport - electric locomotive pioneer
• Charles Grafton Page - electrical pioneer
• Battery powered railcars

External links

• Battery is our business
• Electric traction
• Electric engines
• Battery is our business
• Railroad tapping into wind and solar power