Three-phase AC railway electrification

Three-phase AC railway electrification was used in Italy, Switzerland and the United States in the early twentieth century.

(However, both regenerative braking and 16+2⁄3 Hz were successfully implemented also for single-phase systems, like for the Swiss Ce 6/8 II and III "Crocodile" type.)

Pole changing and cascade (concatenation) working was used to allow two or four different speeds, and resistances (often liquid rheostats) were required for starting.

[9] This motor characteristic led to a mishap in the Cascade Tunnel to a GN east-bound freight train with four electric locomotives, two on the head and two pushing.

A three-phase system is also prone to larger lengthwise gaps between sections, owing to the complexity of two-wire overhead, and so a long pickup base is needed.

In Italy this was achieved with the long bow collectors reaching right to the ends of the locomotive, or with a pair of pantographs, also mounted as far apart as possible.

The dual conductor pantograph system is used on four mountain railways that continue to use three-phase power (Corcovado Rack Railway in Rio de Janeiro, Brazil, Jungfraubahn and Gornergratbahn in Switzerland and the Petit train de la Rhune in France).

Train using a multiphase electrification system on the Petit train de la Rhune , France
Two Italian three-phase locomotives Class E.432
In some places in Italy, three-phase catenary was reconfigured to work on the standard 3000 V DC electrification scheme in Italy, as seen here at the defunct San Lorenzo al Mare station in Liguria in 1991 (closed 2001). Regular DC catenary is on the left while reconfigured three-phase catenary is on the middle and on the right.
FS Class E.550 (Italy 1906–65)
FS Class E330 (Italy 1914–63). Note the long bow collectors, with their pickup points at the far ends of the locomotive.
3-phase pantograph on a Corcovado Rack Railway train in Brazil