Electro-diesel locomotive


An electro-diesel locomotive is a type of locomotive that can be powered either from an electricity supply or by using the onboard diesel engine. For the most part, these locomotives are built to serve regional, niche markets with a very specific purpose.

Overview

Electro-diesel locomotives are used to provide continuous journeys along routes that are only partly electrified without a change of locomotive, avoid extensive running of diesel under overhead electrical wires and giving a solution where diesel engines are banned. They may be designed or adapted mainly for electric use, mainly for diesel use or to work well as either electric or diesel.
In most cases, electro-diesel locomotives use diesel–electric transmission and the same traction electric motors when moving in both diesel and electric mode, although with different power source. However, locomotives with diesel-mechanical or diesel-hydraulic transmission and separate electric motors were also created.
Note that, as well as the electric multiple unit and diesel multiple unit, where no discrete locomotive is present, an electro-diesel multiple unit train is called electro-diesel multiple unit or bi-mode multiple unit.

Types

Primarily electric

This is effectively an electric locomotive with a relatively small auxiliary diesel prime mover intended only for low-speed or short-distance operation. For economy, the diesel engine and its generator are considerably smaller than the electric capacity, which occupies most of the interior space of a locomotive. Unlike typical diesel locomotives, where the diesel engine is located in the center of the frame, in mainly electric dual-mode locomotives the auxiliary diesel engine and generator can be located at the side of the engine room.
The output power of a diesel-generator in mainline locomotives of this type is similar to the power of engines of small shunting locomotives and is significantly smaller than the nominal power of electric motors when they are powered from the electric supply. For example, the Southern Railway types were of or 'Type 3' rating as electrics, but only as diesels. Later classes had as much as on electric power, but still the same diesel engines. Despite this large difference, their comparable tractive efforts were much closer and so they could start and work equally heavy trains as diesels, but not to the same speeds.
These locomotives are usually operated on electrified railway lines that have non-electrified sections in the short final part of the route, the so-called "last mile". That can be a small branch lines, stations with non-electrified siding tracks or tracks with another type of electrification, lines at cargo terminals, industrial facilities, construction sites, wharves, factories, mines, quarries at loading points where overhead lines cannot be used due to the need to load cargo. That eliminates the need to change a mainline locomotive to a shunter locomotive. Also in case of a third rail electrification, these locomotives can be used to cross non-electrified gaps or tracks with unpowered third rail.
The Southern Region of British Railways used mainly-electric dual-mode locomotives from the 1960s onwards to cross non-electrified gaps and to haul boat trains that used tramways at the ports of Southampton and Weymouth, and also at freight yards. Some of these locomotives were originally built as electro-diesel locomotives at the factory, others were converted from electric locomotives.
Since the 2010s, in continental Europe, several locomotive manufacturers have started to produce electric locomotives with an optional small "last mile diesel", and this name was getting popular. These are electric locomotives with a small diesel engine of truck type, used in low speed, low gear, for operation at small flat freight yards or with short freight trains at branch lines, eliminating the need for a shunter locomotive.
At the same time, locomotives with more powerful diesel engines, which are also capable of self-powered operations when hauling a normal freight train at low speeds, were also produced. In terms of power, locomotives of this class takes an intermediate position between primarily electric locomotives with auxiliary diesel engines and fully dual-mode locomotives, though they are mostly limited to last mile operations.

Primarily diesel

This is effectively a diesel locomotive with auxiliary electric capacity for power supply from electric network, usually operating from a low-voltage catenary, where non-electric traction is banned. These locomotives are generally based on conventional diesel-electric locomotives and can be converted relatively easily by adding current collectors, contactors and voltage regulation equipment when powered from an electric supply. Due to the low input voltage and current limitations in electric mode, the power output on the traction motors and the maximum speed of such a locomotive are lower than when powered by a diesel engine.
The primary function for these models is to provide a "one-seat ride" between the electrified and non-electrified sections of a rail system or to allow trains to run through tunnels or other segments of track where diesel locomotives are generally prohibited due to their production of exhaust.
In the United States, such locomotives are used for certain trains servicing the New York City terminals of Grand Central Terminal and Penn Station, as the various rail tunnels into Manhattan have exhaust restrictions. Once out of the tunnels, the engines are started and operation is as a normal diesel locomotive.

Full dual-mode

This type of dual-mode locomotives has a high power and traction force at home running at high speeds both "under the wires" and under diesel power. These locomotives normally operate under pure electric traction where possible, and use the diesel engines to extend the journeys along non-electrified sections which would not be cost effective to electrify. They may also be used on long cross-country routes to take advantage of shorter sections of electrified main lines.
Historically, most mainline dual-mode locomotives have had mainly electric or mainly diesel designs, as it was difficult to fit a powerful diesel engine and powerful electric capacity into a single unit while maintaining the permissible axle load. Mostly, full-fledged dual-mode electric-diesel locomotives were either small shunting and narrow-gauge locomotives with a low-powered diesel engine, which had a comparable power outputs in electric and diesel modes, or two-unit industrial freight locomotives with separate electric and diesel sections, united by a common control system and power supply for traction electric motors.
Since the 2010s, thanks to the development of technologies and the emergence of sufficiently powerful and compact high-speed turbocharged diesel engines, as well as compact power electronics, it has become possible to create single full-fledged dual-mode and even tri-mode locomotives with an acceptable axle load. With modern electronics, it is much easier to construct such locomotives.
The electrical equipment and the diesel generator usually occupy more or less equal space in the engine room, depending on the power and size of the diesel. Although the power output of the diesel generator and traction electric motors of such locomotives is usually significantly lower than when powered from overhead lines in pure electric mode, it is still sufficient to maintain normal speed with a train. For example, in Stadler Euro Dual locomotives, the diesel engine power can vary from in diesel mode and up to in electric mode.

Hybrid locomotive

A specialized type of electro-diesel locomotive is the hybrid locomotive. Here, the electricity comes from a battery charged by the diesel engine rather than from an external supply. An example is the Green Goat switcher GG20B by Railpower Technologies, a subsidiary of R.J. Corman Railroad Group since 2009.

List of electro-diesel locomotives by country

Europe

Georgia

  • ETG, an experimental electro-diesel shunter with hydraulic transmission converted at Tbilisi locomotive depot in 1967 from AMG5 diesel-hydraulic shunting locomotive by replacing its diesel prime mover with less powerful diesel engine and two electric motors from VL22m locomotive. The locomotive operated for several years and was withdrawn in the 1970s.

    Germany

  • Gmeinder class 478.6 diesel and third-rail.
  • Voith Futura, a 2009 CREAM Project concept locomotive rebuilt from DB 240 002.
  • Bombardier TRAXX "Last Mile Diesel", mainly electric. Orders signed 2010, to be delivered probably 2012.
  • Siemens Vectron Dual Mode

    Poland

  • Pesa 111Ed Gama Marathon – mainly electric, with auxiliary diesel engine enabling last-mile operation on non-electrified tracks. Gama Marathon was first presented in 2012 at InnoTrans Berlin. The locomotive then underwent a series of tests with rail operators Lotos Kolej and PKP Intercity, after successful conclusion it was offered on the market. In July 2015 the Polish train-operating company Locomotiv bought the prototype and signed order for further two Marathons.
  • Newag Dragon – version of this electric freight locomotive for the Freightliner's Polish branch, Freightliner PL Sp. z o.o. is equipped with auxiliary diesel engine.
  • Newag Griffin – a version of this electric freight locomotive, leased to Lotos Kolej in 2017 for 7 years with a provision to extend the lease, is equipped with auxiliary diesel engine.

    Russia

In Russia, a number of electro-diesels were built which had both pantographs and diesel prime movers. These included:
Narrow-gauge dual-mode locomotives:
Industrial freight locomotives:
  • OPE1, full dual-mode freight locomotives, used mostly in quarries and some another industrial railways with overhead wires, produced by Novocherkassk Electric Locomotive Plant. Each locomotive consists of two sections with dedicated electric and diesel power equipment, which can operate as a standalone single-ended electric or diesel locomotives, some of them are also equipped with a motorized dump car.
  • OPE1A, OPE1B and PE3T, full dual-mode freight steeplecab locomotives for quarry railways with overhead wires with AC electrification or , produced by Dnipro Electric Locomotive Plant, Ukraine. A complete locomotive consists of primary electric A unit with a cab, one diesel-electric B-unit with a lowered body and one motorized dump car, however most OPE1A locomotives were produced without diesel B-units and with two motorized dump cars.
  • LEW EL10 EL20, mainly electric locomotives for quarry railways with overhead wires. Each locomotive is equipped with two motorized dump cars.
Mainline freight locomotives:
  • 2EV120, mainly electric two-unit freight locomotive, produced by Engels Locomotive Plant and derived from Bombardier TRAXX. Locomotive using both and overhead wires and can be equipped with auxiliary "Last Mile Diesel".