SWISS catenary specialist Furrer + Frey, working with southwest Germaen energy utility company Stadtwerken Tübingen, has developed a rapid charging system for mainline trains, which they say could provide an alternative to “electrification islands” or discontinuous electrification to enable BEMUs to operate on otherwise non-electrified lines.

The “Voltap” system is similar in concept to technology already in use in several countries for electric buses and trams. However, this system is designed for high-voltage ac electricity supplies of up to 1.2 MW compared with the usual 850V dc supplied by most tram and bus applications.

The Voltap system provides the charge via a short section of rigid overhead conductor rail, with initial tests undertaken in Tübingen, Germany, suggesting that a standard 50Hz energy utility supply at 10kV or 20kV ac can be converted via a transformer to 15kV in Germany or 25kV elsewhere.

The tests, monitored by TÜV Süd, suggest that the ‘standard’ industrial supply at 50Hz can be used for 15kV traction supply rather than the specialist 16.66Hz normally used for railway traction current in Germany and some other countries. This is possible as the charging process will only be undertaken whilst stationary and modern batteries are designed for 50Hz supplies.

Further tests with a BEMU are due to take place.