To ensure that railway operations – over 10,000 trains run on the Schweizer Bundesbahnen (SBB) network every day – run reliably and safely, the catenaries must be regularly inspected, maintained and, if necessary, repaired or replaced. Special maintenance vehicles are used here to transport lifting platforms, cranes, machinery and the necessary material to the maintenance section – usually at night when trains are not running. A locomotive pulls the maintenance vehicles to the construction site, where they are powered by diesel engines. As the catenaries are without electricity during the work, the motors often run all night – at least in idle throttle. This is because the fossil fuel not only moves the vehicle, but also drives generators for maintenance equipment – such as welding equipment – and vehicle heating. Swiss Federal Railways now wants to massively reduce these CO₂ emissions. 

Thanks to a hybrid drive consisting of SINAMICS S120 and SIMATIC standard components, the fuel consumption of maintenance rail vehicles for overhead line construction is halved. With the powerful batteries, the work equipment can be operated purely electrically and the air remains clean. Where previously a large diesel engine spent a lot of time at a less efficient idle, it is now used exclusively for charging the batteries and always runs at the ideal operating point – even its residual energy flows into the batteries. As soon as these are sufficiently charged, the motor switches off automatically.   The hybrid rolling stock can be operated very efficiently with a synchronous motor and the SINAMICS S120 drive system. In combination with the SIEMENS Smart Power Management (SPM) solution, the SINAMICS S120 Active Line Module (ALM) power and regeneration units can be used for battery charging as well as off-grid operation.