First Modernised SSB LRVs

In February 2019, Stuttgarter Straßenbahnen AG (SSB) awarded Voith a contract to modernise and renew the traction inverters of 50 Type S-DT 8.10 and S-DT 8.11 light rail vehicles. In October 2020, the first two of Type S-DT 8.10 (3303/3304 and 3335/3336) have been commissioned. They are scheduled to return to regular service on 30 November.

SSB currently operates 204 LRVs of the specific S-DT 8 Stuttgart design, which were built by Adtranz and Siemens between 1999 and 2005. The 1,435 mm gauge 750 V DC 80 km/h vehicles have a (Bo’) (Bo’) + (Bo’) (Bo’) axle arrangement and a 1,020 kW maximum power. Their length is 38.6 m and tare weight 55.6 t.

Each S-DT 8 includes four traction inverters, which are installed to power all axles, necessary for Stuttgart network topography with gradients of up to 85 ‰. The modernisation of a total of 210 traction inverters (ten are spare inverters) allows a significant reduction in susceptibility to faults and a consistently high availability of the vehicles for the second half of their service life. As part of the modernisation, both the mechanical refurbishment of the housings, switching elements, braking resistors and chokes as well as the replacement of the power electronics are being incorporated.

The new Type DI1000-4AU-01 inverters are being produced at Voith St. Pölten works in Austria and fitted in the vehicles at the SSB Heslach and Möhringen tram depots. All newly installed components and technical solutions must fit perfectly with the existing vehicle interfaces. Voith has therefore developed a power module that draws on proven components but also takes into account all mechanical and electrical interfaces of the existing inverter. 

Targeted optimisation measures like demand based fan control led to a reduction of energy consumption as well as to a reduction in noise levels. Moreover, weight has been saved - each new inverter now weighs 510 kg compared to 540 kg in the initial version. The Voith project is to be completed by the end of 2025.