Under Europe's incompatible catenary voltages a review of multi-system traction technology

The electrification of European railways started very early in the 20th century, using different DC and AC technologies. But only after the onset of the common European Market, the need for traction material arose, able to operate in the four remaining supply systems freely. While with the classic traction technologies special (and uneconomic) constructions were needed, the three-phase drive technology with Voltage Source Inverters and Four-Quadrant line-side converters enabled by its modularity rather simple and economic solutions. The introduction of 6.5-kV IGBTs allowed further standardization.