Head end power or
electric train supply (
ETS) is a
rail transportRail transport is a means of conveyance of passengers and goods by way of wheeled vehicles running on rail tracks. In contrast to road transport, where vehicles merely run on a prepared surface, rail vehicles are also directionally guided by the tracks they run on...
term for the electrical power distribution system on a passenger train. The power source, usually a locomotive at the front or “
head” of a train or a generator car, generates all the electricity used for lighting, electrical and other "hotel" needs. The maritime equivalent is
Hotel Electric PowerHotel Electric Power is a maritime term referring to electricity generated and used aboard a ship for purposes other than propulsion such as lighting, communications, climate control, refrigeration, water desalination and treatment, entertainment, etc...
(HEP).
United Kingdom
Originally, trains hauled by a
steam locomotiveA steam locomotive is a railway locomotive that produces its power through a steam engine. These locomotives are fueled by burning some combustible material, usually coal, wood or oil, to produce steam in a boiler, which drives the steam engine...
would be provided with a supply of steam from the locomotive's boiler for heating the carriages. When
diesel locomotiveA diesel locomotive is a type of railroad locomotive in which the prime mover is a diesel engine, a reciprocating engine operating on the Diesel cycle as invented by Dr. Rudolf Diesel...
s and electric locomotives replaced steam, the steam heating was then supplied by a
steam-heat boilerSteam generator is the term used to describe a type of boiler used to produce steam for climate control and potable water heating in railroad passenger cars...
. This was oil-fired (in diesel locomotives) or heated by an electric element (in electric locomotives). Oil-fired steam-heat boilers were appallingly unreliable. They caused more locomotive failures on any class to which they were fitted than any other system or component of the locomotive, and this was a major incentive to adopt a more reliable method of carriage heating.
At this time, lighting was powered by
batteriesAn electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power...
which were charged by a
dynamoIn electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric charge to flow through an external electrical circuit. It is analogous to a water pump, which causes water to flow...
underneath each carriage when the train was in motion, and
buffet carA buffet car is a passenger car of a train, where snacks and beverages can be bought at a counter and consumed. Typically, passengers are not allowed to consume brought-along food and drinks in the car, and are therefore only able to eat in this area by buying their food in the car.- Further...
s would use
bottled gasBottled gas is a term used for substances which are gaseous at standard temperature and pressure and have been compressed and stored in carbon steel, stainless steel, aluminum, or composite bottles known as gas cylinders.-Gas state in cylinders:...
for cooking and water heating.
On modern
Diesel multiple unitA diesel multiple unit or DMU is a multiple unit train consisting of multiple carriages powered by one or more on-board diesel engines. They may also be referred to as a railcar or railmotor, depending on country.-Design:...
trains, such as the
Virgin TrainsVirgin Trains is a train operating company in the United Kingdom. It operates long-distance passenger services on the West Coast Main Line between London, the West Midlands, North West England, North Wales and Scotland...
VoyagerThe Class 220 Voyager are a class of diesel-electric high-speed multiple-unit trains built by Bombardier Transportation in 2000 and 2001....
, the engine mounted below each vehicle provides power for that vehicle.
Electric Train Heat (ETH) and Electric Train Supply (ETS)
Later diesels and
electric locomotiveAn electric locomotive is a locomotive powered by electricity from overhead lines, a third rail or an on-board energy storage device...
s were equipped with
Electric Train Heating (
ETH) apparatus, which supplied electrical power to the carriages to run electric heating elements installed alongside the steam-heat apparatus, which was retained for use with older locomotives. Later carriage designs abolished the steam-heat apparatus, and made use of the ETH supply not only for heating, but also to power lighting, ventilation,
air conditioningAn air conditioner is a home appliance, system, or mechanism designed to dehumidify and extract heat from an area. The cooling is done using a simple refrigeration cycle...
, fans, sockets and kitchen equipment in the train. In recognition of this ETH was eventually renamed
Electric Train Supply (
ETS).
Each coach has an index relating to the maximum consumption of electricity that that coach could use. The sum of all the indices must not exceed the index of the locomotive. One "ETH index unit" equals 5 kW; a locomotive with an ETH index of 95 can supply 475 kW of electrical power to the train.
North America
During the
age of steamA steam locomotive is a railway locomotive that produces its power through a steam engine. These locomotives are fueled by burning some combustible material, usually coal, wood or oil, to produce steam in a boiler, which drives the steam engine...
, cars were heated by low pressure
saturated steamIn thermodynamics, the state of saturation of a fluid indicates that the fluid is at its boiling point temperature. This term can be applied in several ways:*Saturated liquid: fully in the liquid state but is about to vaporize....
supplied by the locomotive. Electricity for car lighting and
ventilationHVAC refers to technology of indoor or automotive environmental comfort. HVAC system design is a major subdiscipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics, and heat transfer...
was derived from
batteriesAn electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power...
charged by axle-driven
generatorIn electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric charge to flow through an external electrical circuit. It is analogous to a water pump, which causes water to flow...
s on each car or from
engine-generatorAn engine-generator is the combination of an electrical generator and an engine mounted together to form a single piece of equipment. This combination is also called an engine-generator set or a gen-set...
sets mounted under the carbody.
The first advance over this system was developed on the
Boston and Maine RailroadThe Boston and Maine Corporation , known as the Boston and Maine Railroad until 1964, was the dominant railroad of the northern New England region of the United States for a century...
, which had placed a number of steam locomotives and passenger cars into dedicated commuter service in
BostonBoston is the capital of and largest city in Massachusetts, and is one of the oldest cities in the United States. The largest city in New England, Boston is regarded as the unofficial "Capital of New England" for its economic and cultural impact on the entire New England region. The city proper had...
. Due to the low average speeds and frequent stops characteristic of commuter operation, the axle generators' output was insufficient to keep the batteries charged, resulting in passenger complaints about lighting and ventilation failures. In response, the railroad installed higher capacity generators on the locomotives assigned to these trains, and provided electrical connections to the cars. The cars used steam from the locomotive for heating.
When diesel locomotives were introduced to passenger service, they were equipped with
steam generatorSteam generator is the term used to describe a type of boiler used to produce steam for climate control and potable water heating in railroad passenger cars...
s to provide steam for car heating. However, the use of axle generators and batteries persisted for many years. This started to change in the late 1950s, during which time the
Chicago and North Western RailwayThe Chicago and North Western Transportation Company was a Class I railroad in the Midwest United States. It was also known as the North Western. The railroad operated more than of track as of the turn of the 20th century, and over of track in seven states before retrenchment in the late 1970s...
removed the steam generators from their
EMD F7The EMD F7 was a Diesel-electric locomotive produced between February 1949 and December 1953 by the Electro-Motive Division of General Motors and General Motors Diesel . It succeeded the F3 model in GM-EMD's F-unit sequence, and was replaced in turn by the F9. Final assembly was at GM-EMD's La...
and
E8The EMD E8 was a , A1A-A1A passenger train locomotive manufactured by General Motors' Electro-Motive Division of La Grange, Illinois. The cab version, or E8A, was manufactured from August, 1949 to December, 1953, and 449 were produced – 446 for U.S., and 3 for Canada...
locomotives in commuter service and installed
diesel generatorA diesel generator is the combination of a diesel engine with an electrical generator to generate electrical energy....
sets. This was a natural evolution, as their commuter trains were already receiving low-voltage, low-current power from the locomotives to assist axle generators in maintaining battery charge. In some cases, commuter cars were equipped with
propanePropane is a three-carbon alkane with the molecular formula , normally a gas, but compressible to a transportable liquid. A by-product of natural gas processing and petroleum refining, it is commonly used as a fuel for engines, oxy-gas torches, barbecues, portable stoves, and residential central...
engine-powered air conditioning. The resulting separate systems of lighting power, steam heat, and engine-driven air conditioning increased the maintenance workload, as well as parts proliferation, thus leading to the full-scale adoption of HEP, where a single power source would handle all these functions.
While commuter fleets were quickly converted to HEP, long distance trains continued to operate with steam heat and battery-powered electrical systems. This gradually changed following the transfer of intercity passenger rail service to
AmtrakThe National Railroad Passenger Corporation, doing business as Amtrak , is a government-owned corporation that was organized on May 1, 1971, to provide intercity passenger train service in the United States. "Amtrak" is a portmanteau of the words "America" and "track". It is headquartered at Union...
, ultimately resulting in full adoption of HEP in the USA and the discontinuation of the old systems.
Following its formation in 1971, Amtrak's initial locomotive purchase was the Electro-Motive (EMD)
SDP40FThe EMD SDP40F was a 6-axle Diesel-electric locomotive built by General Motors Electro-Motive Division from 1973 for Amtrak service. Power was provided by an EMD 645E3 16-cylinder turbocharged Diesel engine, which generated 3000 tractive horsepower .-Origins:The SDP40F was the first locomotive...
, an adaptation of the widely-used
SD40-2The EMD SD40-2 is a C-C locomotive produced by EMD from 1972 to 1989.The SD40-2 was first introduced in January 1972 as the mid-range offering in EMD's six-axle "Dash-2" series, competing against the GE U30C and the MLW M630...
3000 horsepower freight locomotive, fitted with a passenger style carbody and steam generating capability. The SDP40F permitted the use of modern motive power in conjunction with the old steam heated passenger rolling stock acquired from private railroads, giving Amtrak time to procure purpose-built cars and locomotives.
In 1975, Amtrak started to take delivery of the all-electric
AmfleetAmfleet is a series of intercity railroad passenger cars built for the operator Amtrak by the manufacturer Budd Company in two series during the late 1970s and early 1980s. Today, Amfleet cars are used extensively throughout the Amtrak system outside the western United States...
car, hauled by
General ElectricGeneral Electric Company , or GE, is an American multinational conglomerate corporation incorporated in Schenectady, New York and headquartered in Fairfield, Connecticut, United States...
(GE)
P30CHThe GE P30CH was one of the first brand-new Diesel-electric locomotives built for Amtrak in the company's early years. The design was based on the GE U30C, but had a cowl carbody like its EMD competitors.25 P30CHs were ordered by Amtrak in 1974, just after Amtrak ordered 40 EMD SDP40Fs in 1973...
and, later, EMD F40PH locomotives, both unit types being equipped to furnish HEP. Following the introduction of the Amfleet fleet, the (also all-electric)
SuperlinerThe Superliner is a double decker passenger car used by Amtrak on long haul trains that do not use the Northeast Corridor. The initial cars were built by Pullman-Standard in the late 1970s and a second order was built in the mid 1990s by Bombardier Transportation...
railcar was placed into operation for servicing long-distance western routes. Amtrak subsequently converted a portion of the steam heated fleet to all-electric operation using HEP, and retired the remaining unconverted cars.
Engine
The HEP generator can be driven by either a separate engine mounted in the locomotive or generator car, or by the locomotive's
prime moverIn engineering, a prime mover is an engine that converts fuel to useful work. In locomotives, the prime mover is thus the source of power for its propulsion. The term is generally used when discussing any locomotive powered by an internal combustion engine...
.
Separate engines
Engine types vary, but in the US, they are mainly
CaterpillarCaterpillars are the larval form of members of the order Lepidoptera . They are mostly herbivorous in food habit, although some species are insectivorous. Caterpillars are voracious feeders and many of them are considered to be pests in agriculture...
3412 V12 and
CumminsCummins Inc. is a Fortune 500 corporation that designs, manufactures, distributes and services engines and related technologies, including fuel systems, controls, air handling, filtration, emission control and electrical power generation systems...
K-Series Inline 6 models. In the past,
Detroit DieselAs a corporation, Daimler Trucks North America has decided to rename the company "DETROIT".Detroit Diesel Corporation is an American-based diesel engine producer headquartered in Detroit, Michigan, USA...
8V-71 and 12V-71 engines were also used. Such engine/generator sets are generally installed in a compartment in the rear of the locomotive that is isolated from the main
engine roomOn a ship, the engine room, or ER, commonly refers to the machinery spaces of a vessel. To increase the safety and damage survivability of a vessel, the machinery necessary for operations may be segregated into various spaces, the engine room is one of these spaces, and is generally the largest...
, drawing fuel from the locomotive's fuel tanks.
Smaller under-car engine/generator sets for providing electricity on short trains are also manufactured, Stadco being one such brand.
Locomotive prime mover
In many applications, the locomotive's prime mover provides both propulsion and head end power. In most cases, the prime mover must run at a constant speed (RPM) to maintain the required 50 Hz or 60 Hz AC line
frequencyFrequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
. For example, an EMD locomotive operating in HEP mode will run the prime mover at a constant 900 RPM (which is full RPM), driving the generator at 1500 RPM (50 Hz) or 1800 RPM (60 Hz) through a gearbox. For noise reduction purposes, the locomotive's main (traction) generator can also be configured to supply HEP, usually at 600 or 720 RPM. However, this mode is only available when the locomotive is stationary.
The advent of power electronics has allowed the prime mover to operate over a larger speed range and still supply a constant HEP voltage and frequency by means of
inverterAn inverter is an electrical device that converts direct current to alternating current ; the converted AC can be at any required voltage and frequency with the use of appropriate transformers, switching, and control circuits....
s.
When derived from the prime mover, HEP is generated at the expense of traction power. For example, the
General ElectricGeneral Electric Company , or GE, is an American multinational conglomerate corporation incorporated in Schenectady, New York and headquartered in Fairfield, Connecticut, United States...
3200 hp P32 and 4000 hp P40 locomotives are derated to 2900 hp, respectively, when supplying HEP.
The
Fairbanks-MorseFairbanks Morse and Company was a manufacturing company in the late 19th and early 20th century. Originally a weighing scale manufacturer, it later diversified into pumps, engines, windmills, locomotives and industrial supplies until it was merged in 1958...
P-12-42The P-12-42, also known as the Speed Merchant, was a streamlined, locomotive built between 1957–1958 by Fairbanks-Morse, specifically to operate on each end of the Talgo train produced by American Car and Foundry...
was one of the first HEP equipped locomotives to have its prime mover configured to run at a constant speed, with traction generator output regulated solely by excitation.
One of the first tests of HEP powered by an EMD locomotive's prime mover was in 1969, on Milwaukee Road
EMD E9The EMD E9 was a , A1A-A1A passenger train-hauling diesel locomotive built by General Motors' Electro-Motive Division of La Grange, Illinois between April 1954 and January 1964. 100 cab-equipped lead A units were produced, along with 44 cabless booster B units. All were for service within the...
#33C, which was converted to have a constant speed rear engine.
Electrical loading
HEP power supplies the lighting,
HVACHVAC refers to technology of indoor or automotive environmental comfort. HVAC system design is a major subdiscipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics, and heat transfer...
, dining car kitchen and battery charging loads. Individual car electrical loading ranges from 20 kW for a typical car to more than 150 kW for a
Dome carA dome car is a type of railway passenger car that has a glass dome on the top of the car where passengers can ride and see in all directions around the train. It also can include features of a coach, lounge car, dining car or observation...
with kitchen and dining area, such as Princess Tours
Ultra-DomeColorado Railcar was a manufacturer of railroad rolling stock, railcars and diesel multiple unit commuter vehicles. Both products come in single- and double-level versions. It shut down in 2008, with its assets being purchased by US Railcar.-History:...
cars operating in
AlaskaAlaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
.
North America
Because of the lengths of trains and the high power requirements, HEP is supplied, in
North AmericaNorth America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, as
three-phaseThree-phase electric power is a common method of alternating-current electric power generation, transmission, and distribution. It is a type of polyphase system and is the most common method used by grids worldwide to transfer power. It is also used to power large motors and other heavy loads...
AC at 480
VThe volt is the SI derived unit for electric potential, electric potential difference, and electromotive force. The volt is named in honor of the Italian physicist Alessandro Volta , who invented the voltaic pile, possibly the first chemical battery.- Definition :A single volt is defined as the...
(standard in the US and for Canada's
Via RailVia Rail Canada is an independent crown corporation offering intercity passenger rail services in Canada. It is headquartered near Montreal Central Station at 3 Place Ville-Marie in Montreal, Quebec....
,
AMTThe Agence métropolitaine de transport is the umbrella organization that plans, integrates, and coordinates public transportation services across Canada's Greater Montreal Region, including the Island of Montreal, Laval , and communities along both the North Shore of the Rivière des Mille-Îles...
(Montreal) and others), 575 V (
GO TransitGO Transit is an inter-regional public transit system in Southern Ontario, Canada. It primarily serves the Greater Toronto and Hamilton Area conurbation, with operations extending to several communities beyond the GTHA proper in the Greater Golden Horseshoe...
, Toronto), or (rarely) 600 V.
TransformerA transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field...
s are fitted in each car for reduction to lower voltages.
United Kingdom
In the UK, ETS is supplied at 800 V to 1000 V AC/DC two pole (400 or 600 A), 1500 V AC two pole (800 A) or at 415 V 3 phase on the
HSTThe InterCity 125 was the brand name of British Rail's High Speed Train fleet. The InterCity 125 train is made up of two power cars, one at each end of a fixed formation of Mark 3 carriages, and is capable of , making the train the fastest diesel-powered locomotive in regular service in the...
.
Russia
Russian cars use electric heating with either 3 kV DC voltage on DC lines or 3 kV AC voltage on AC lines provided by locomotive's main transformer. Newer cars are mostly made by Western-European manufacturers and are equipped similarly to RIC cars.
Europe (RIC cars, except Russia and UK)
RICThe International Coach Regulations or RIC were first agreed in 1922 and covered the international use of railway passenger coaches between European railways. Until 1982 the RIC was looked after by the Swiss Federal Railways, but since then the International Union of Railways has taken...
cars must be able to be supplied at all the following four voltages: 1,000 V AC 16 2/3 Hz, 1,500 V AC 50 Hz, 1,500 V DC and 3,000 V DC. The first one is used in Norway, Sweden, Germany, Austria and Switzerland, where the
catenary systemOverhead lines or overhead wires are used to transmit electrical energy to trams, trolleybuses or trains at a distance from the energy supply point...
15 kV 16 2/3 Hz is used. The second one (1.5 kV AC) is used in countries which use catenary system (Russia, Denmark, France, UK, Italy and Finland). In both cases, the proper voltage is provided by the locomotive's main transformer or an AC alternator in diesel locomotives. In countries using DC power (either 1.5 kV or 3 kV DC), the voltage collected by the pantograph is supplied directly to the cars. (Russia, Belgium, Italy, Poland, Slovakia and Spain use 3 kV and France and Holland use 1.5 kV.)
Older European cars used high voltage (or steam) only for heating, while light and fans power was provided by axle-driven generator. Today, with the progress in solid state electronics (Thyristors and IGBTs), most cars have switching power supply, which takes any RIC voltage (1.0 – 3.0 kV) and supplies the car with all the needed lower voltages. Low voltages differ depending on manufacturers, but typical values are:
- 24 V – 48 V DC for on-board electronics (powered from battery when HEP disabled)
- 24 V – 110 V DC for feeding fluorescent lamps' electronic ballasts (powered from battery when HEP disabled)
- Single phase 230 V AC for passenger sockets, refrigerators etc. (sometimes powered from battery, as above)
- Three phase 400 V AC for air cond. compressor, heating, ventilation fans (air cond. is nowadays never powered from battery due to power consumption, fans are)
Electric heating was typically high-voltage powered, but the unusual voltages are not common on the market and the equipment is expensive.
A standard RIC-compliant heater has six resistors which are being switched accordingly to voltage: 6 in series(3 kV DC), 2 × 3 in series (1.5 kV AC or DC) or 3 × 2 in series (1 kV AC). The selection and switching of a proper configuration is automatic for the sake of safety. Passengers can only operate
thermostatA thermostat is the component of a control system which regulates the temperature of a system so that the system's temperature is maintained near a desired setpoint temperature. The thermostat does this by switching heating or cooling devices on or off, or regulating the flow of a heat transfer...
.
China
In China, ETS is supplied at 380 V three-phase by generator car, but 600 V DC on 25T passenger car.
Alternatives
Although most locomotive-hauled trains take power directly from the locomotive, there have been examples (mainly in continental
EuropeEurope is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
) where restaurant cars would take power directly from the
overhead wiresA railway electrification system supplies electrical energy to railway locomotives and multiple units as well as trams so that they can operate without having an on-board prime mover. There are several different electrification systems in use throughout the world...
. For example, the German restaurant cars WRmz 135 (1969), WRbumz 139 (1975) and ARmz 211 (1971) were all equipped with pantograph.
Finnish dining/catering cars have a built-in Diesel-generator set that is used even when a locomotive-supplied power is available.
When the State of Connecticut first started
Shore Line EastShore Line East is a commuter rail service operating in southern Connecticut, USA. A fully owned subsidiary of the Connecticut Department of Transportation , SLE provides service seven days a week along the Northeast Corridor from New London west to New Haven, with continuing service to Bridgeport...
they were using in many cases old freight equipment which were not able to supply HEP. With the actuation of locomotives with HEP these have since been removed.
Where a passenger train has to be hauled by a locomotive with no HEP supply (or an incompatible HEP supply) a separate generator van may be used such as on the
Amtrak CascadesThe Amtrak Cascades is a passenger train route operated by Amtrak in partnership with the states of Washington and Oregon in the Pacific Northwest of the United States and the province of British Columbia in Canada...
train or
Iarnród ÉireannIarnród Éireann is the national railway system operator of Ireland. Established on 2 February 1987, it is a subsidiary of Córas Iompair Éireann . It operates all internal intercity, commuter and freight railway services in the Republic of Ireland, and, jointly with Northern Ireland Railways, the...
's CAF Mark 4 Driving Van Trailer (with twin MAN 2846 LE 202 (320 kW) / Letag (330 kVA) engine / generator sets, assembled by GESAN).
KiwiRailKiwiRail Holdings Limited is the rail operations subsidiary of the New Zealand Railways Corporation, which trades as KiwiRail. Headquartered in Wellington, New Zealand, KiwiRail is the largest rail transport operator in New Zealand. Since July 2010 John Spencer has been the Chairman...
(New Zealand) use
AG classThe NZR FM guards van is a rail vehicle in New Zealand originally used on freight trains but now used primarily on passenger trains, reclassified AG.-First batch, 1977:...
luggage-generator vans for their
Tranz ScenicTranz Scenic is the long-distance passenger train brand of KiwiRail, formed from the New Zealand Railways Corporation InterCity Rail services. Tranz Scenic was renamed along with the other operating divisions of Tranz Rail in 1995...
passenger services;
Tranz MetroTranz Metro, part of KiwiRail, is the operator of Metlink suburban trains owned by the Greater Wellington Regional Council in the Wellington Region of New Zealand....
on the Wairarapa line use SWG class passenger carriages with part of the interior adapted to house a generator.
In the future, the old RIC- voltages will be replaced by the much more cost-effective solution with 50 or 60 Hz three-phase 400/415 V (50 Hz) or 480 V (60 Hz). Three-phase is the backbone of the global power network and most electrical power equipment is today designed for three-phase supply. For example, in UK and Sweden the high-speed trains IC125 and X2000 have 50 Hz 3-phase power bus.
External links