Electro-diesel locomotive


An electro-diesel locomotive is 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 the wires, and giving 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.
Note that, as well as the electric multiple unit and diesel multiple unit, where no discrete locomotive is present, even electro-diesel multiple units exist.

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. Some of these, such as the British Rail Class 74, were converted from electric locomotives. The Southern Region of British Railways used these locomotives to cross non-electrified gaps and to haul boat trains that used tramways at the ports of Southampton and Weymouth. For economy, the diesel engine and its generator are considerably smaller than the electric capacity. The Southern types were of 1,600 hp or 'Type 3' rating as electrics, but only 600 hp as diesels. Later classes had as much as 2,500 hp 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.

Primarily diesel

This is effectively a diesel locomotive with auxiliary electric motors, usually operating from 750 V DC third rail where non-electric traction is banned. 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; 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

With modern electronics, it is much easier to construct an electro-diesel locomotive or multiple-unit which is equally at home running at high speeds both "under the wires" and under diesel power. These will 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.

Europe

Germany

An experimental electro-diesel locomotive, DEL120, was built by London Underground in 1940 but was not a success. Two types have been built whose electricity source was a 750 V DC third rail.
Electro-diesel locomotives whose electricity source is overhead line include:
In Russia, a number of electro-diesels were built which had both pantographs and diesel prime movers. These included:

Canada

Several, primarily diesel locomotive types and a multiple-unit have been built to operate off a third rail into the New York City terminals of Grand Central Terminal and Penn Station. The following are in service:
, US-CT
The following were retired from New York City service:

South Africa

India


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.