Modern rotary converters for railway applications

Electrically-powered railway traction in many countries of the world use single-phase, low-frequency systems. In the United States it is 25 Hz, whereas in Europe 16.67 Hz is applied. Supplying this single-phase energy is done by different means. Dedicated generators driven by hydraulic, steam and gas turbines are applied on the networks. Frequency converters are also applied to transfer energy from the three-phase public grid to the single-phase railway system. Static frequency-converter technology has emerged in recent years as an alternative to rotary equipment for exchanging energy between the railway and public grids. At the same time, rotating equipment technology has advanced. So far, the rotating equipment appears to retain sufficient advantages over the static options that most railway system owners, at least in Europe, continue to install rotary converters. This paper highlights some of the salient issues involved in choosing between rotary and static power frequency converters, with an emphasis on the most recent designs applied in Europe and their potential application in the United States.