Three-phase AC railway electrification was used in Italy, Switzerland and the United States in the early twentieth century. Italy was the major user, from 1901 until 1976, although lines through two tunnels also used the system; the Simplon Tunnel between Switzerland and Italy from 1906 to 1930 (but not connected to the Italian system), and the Cascade Tunnel of the Great Northern Railway in the United States from 1909 to 1939. The first standard gauge line was in Switzerland, from Burgdorf to Thun (), from 1899 to 1933.
Advantages
The system provides regenerative braking with the power fed back to the system, so is particularly suitable for mountain railways (provided the grid or another locomotive on the line can accept the power). The locomotives use three-phase induction motors. Lacking brushes and commutators, they require less maintenance. The early Italian and Swiss systems used a low frequency ( Hz), and a relatively low voltage (3,000 or 3,600 volts) compared with later AC systems.
Disadvantages
The overhead wiring, generally having two separate overhead lines and the rail for the third phase, was more complicated, and the low frequency used required a separate generation or conversion and distribution system. Train speed was restricted to one to four speeds, with two or four speeds obtained by pole-changing or cascade operation or both.
Historical systems
The following is a list of the railways that have used this method of electrification in the past:
The Cascade Tunnel of the Great Northern Railway. The Ferrovia della Valtellina in Italy. The Giovi Railway between Genoa and Pontedecimo in Italy. The Italian part of the Mont-Cenis line Turin–Modane. Many other lines in Northern Italy. The Santa Fe - Gergal line in Spain. The Burgdorf–Thun railway in Switzerland. The Simplon Tunnel between Switzerland and Italy.
Current systems
The system is only used today for rack (mountain) railways, where the overhead wiring is less complicated and restrictions on the speeds available less important. Modern motors and their control systems avoid the fixed speeds of traditional systems, as they are built with solid-state converters.
The four current such railways are
The Corcovado Rack Railway in Rio de Janeiro Brazil. The Gornergratbahn in Switzerland. The Jungfraubahn in Switzerland. The Petit train de la Rhune in France, still using the original locomotives of 1912
All use standard frequency (50 Hz, or 60 Hz (Brazil)) rather than low frequency, using between 725 and 3,000 volts.
Voltage and frequency
This list shows the voltage and frequency used in various systems, historical and current.
Various, Siemens Factory Experiments 1892
200 V / 25 Hz Panama Canal 1915
350 V / 40 Hz Lugano Tramway 1895
460 V / 60 Hz Panama Canal Authority, date unknown
500 V / ??Hz Ganz Factory Experiment 1896
550 V / 40 Hz Gornergratbahn, at opening, 1898
600 V / 60 Hz Taoyuan International Airport Skytrain, at opening, 2003
600 V / 50 Hz Bukit Panjang LRT line, at opening, 1999
650 V / 50 Hz Zhujiang New Town APM System, at opening, 2010
725 V / 50 Hz Gornergratbahn, current
750 V / 40 Hz Burgdorf–Thun railway, 1899–1933
750 V / 40 Hz Hasle-Rüegsau–Langnau railway, 1919–1932
1,125 V / 50 Hz Jungfrau Railway
3,000 V / 15 Hz Ferrovia della Valtellina 1902 - 1917
3,300 V / 16.7 Hz Galleria del Sempione, SBB 1906 - 1930
3,000 V / 15.8 Hz Valtellina FS 1917 - 1930
3,600 V / 16.7 Hz Valtellina FS 1930 - 1953
3,600 V / 16.7 Hz Genoa-Turin, Turin-Frejus-Modane Gallery (F) and other lines in Piedmont and Liguria from 1910 to 1976 3,600 V / 16.7 Hz Trento-Bolzano-Brennero, Bolzano-Merano FS 1929 - 1965 3,600 V / 16.7 Hz Genova-La Spezia e Fornovo FS 1926 - 1948 3,600 V / 16.7 Hz Sondrio-Tirano (Ferrovia Alta Valtellina) 5,200 V / 25 Hz Gergal-SantaFe FC Sur - Spagna 6,600 V / 25 Hz Cascade Range, Great Northern Railway (U.S.), 1909 - 1927 7,000 V / 50 Hz Experiments, Torino-Bussoleno FS 1927 - 1928
Converter systems
This category does not cover railways with a single-phase (or DC) supply which is converted to three-phase on the locomotive or power car, e.g., most railway equipment from the 1990s and earlier using solid-state converters. The Kando system of the 1930s developed by Kálmán Kandó at the Ganz Works, and used in Hungary and Italy, used rotary phase converters on the locomotive to convert the single-phase supply to three phases, as did the Phase-splitting system on the Norfolk and Western Railroad in the United States.