Three-phase motor in railway traction

The first use of the three-phase traction motor was on systems which supplied three-phase power direct to the locomotive, with two contact wires above each track. This system was later replaced either by single-phase AC systems using AC commutator motors, or by high voltage DC railways. In the United States, Alexanderson introduced the split-phase technique, using a locomotive mounted single-phase motor coupled to a three-phase generator. The methods used before 1960 for supplying three-phase traction motors needed complex fixed works, or else they required locomotive mounted equipment which was heavy and large. Between 1962 and 1965, Brush pioneered current-inverter three-phase traction using a diesel-electric locomotive as a test bed. A Co-Co diesel-electric locomotive successfully introduced three-phase traction motor technology into modern practice in 1971. The DB Class 120 electric locomotive established current-inverter technology, and the asynchronous motor, in modern traction between 1980 and 1982. By the mid-1980s there were accepted as standard practice.