Rail Power Supplies Going More Power Electronic [Technology Leaders]

In recent years, interest has risen in using electrified rail operations as an environmentally friendly and efficient way of producing passenger and freight services. New high-speed lines are being designed and built throughout Europe and China, and there is also an increasing interest in high speed rail services in southeast Asia and the United States. To meet this demand, the electrification of railways has rendered increased interest both for new lines and for upgrading existing systems to higher power capacity. Historically, the first rail electrifications were designed as low-voltage dc systems, where the dc voltage was typically generated by dc generators. The limitations in the voltage capability of dc machines and related equipment limited the voltage considerably. More than 100 years later, we still have dc traction systems generated by rectifiers connected to the three-phase grid with voltages in the range of 650 or 750 V up to 3 kV. Because of large voltage drops and excessive losses, it is required that the connecting points to the three-phase system are located with a relatively short mutual distance.