Multi-system (rail)

A Multi-system locomotive, also known as a multi-system electric locomotive, multi-system electric multiple unit, or multi-system train, is an electric locomotive which can operate using more than one railway electrification system. Multi-system trains provide continuous journeys over routes which are electrified using more than one system.

A multi-system locomotive is useful for providing a single journey over multiple electrification systems without interruption, either from requiring passengers to change trains or from changing locomotives. Such conditions can occur where a train crosses national boundaries and each country has implemented a different electrification system.

Prior to 1945 there was little demand for multisystem locomotives in Europe. From the 1950s onwards the formation of the European Communities and the consequent increase in the amount of cross border traffic, and the addition of a 25 kV 50 Hz AC system in France in addition to the older 1.5 kV DC system both gave rise to new needs for multivoltage locomotives. Very high capital costs prevent or hinder the adoption of a standard railway electrification system.

At the beginning of the 21st century railway legislation in Europe (the First Railway Package and Second Railway Package, and the creation of a Trans European Rail Freight Network) liberalised cross border freight traffic, giving rise to demand for locomotives to work between European Union countries with different electrification systems and creating a practically new market for multivoltage locomotives such as Bombardier's TRAXX. However increased cost of purchase and maintenance, along with costs of different safety system installations for cross-border work, have reduced the economic viability of multisystem vehicles versus the use of single voltage machines and locomotive changing.

In India 1500 V DC and 25 kV 50 Hz is used for main line trains. The 1500 V DC overhead system (negative earth, positive catenary) is used around Mumbai. The Mumbai region is the last bastion of 1500 V DC electrified lines on Indian Railways. The Western Railway route from Mumbai Central is now completely changed to 25 kV AC. The 25 kV AC system with overhead lines is use throughout the rest of the country. The dual-voltage WCAM series locomotives haul intercity trains out of Mumbai DC suburban region. The new AC/DC EMU rakes used in Mumbai are also designed to operate with both DC and AC traction as the Mumbai area switches over to the 25 kV AC system which has provided access to the locomotives having AC Traction motors to serve in the suburbs.

...
Wikipedia