ABSTRACT
The possible combinations and topologies have been described in Chapter 2. The electrical source is normally the most signicant choice and the one that is usually imposed by the track infrastructure owner. An electrical overhead system offers a clear operational cost advantage but with high initial capital costs. Once a decision is made as to the power source, the remaining choices relate to the traction motors and their supporting power conditioning. The AC machines, and generally squirrel-cage induction machines, are the dominant technology choice for modern designs. The AC machine is cheaper and much more robust than the DC machine. The existence of affordable high-performance inverters and inverter control strategies allows an AC machine to be controlled as easily as a DC machine. Induction machines, driven by gate-turn-off-based inverters, were reported in railway applications from 1984 onwards [1]. Since that time, the DC traction motors have been steadily displaced; however, signicant numbers of DC traction motors are still in service in legacy ¬eets.
