Electrify to decarbonize

For railway operations to function reliably and safely – more than 10,000 trains run daily on the SBB network – the overhead lines must be regularly inspected, maintained and, if necessary, repaired or replaced. Special maintenance vehicles are used for this purpose, which transport lifting platforms, cranes, machines and the required material to the maintenance section – usually at night when the timetable is paused. A locomotive pulls the maintenance vehicles to the construction site, where they are operated with diesel engines. Recently, five hybrid rail vehicles have been in use for overhead line work, powered by a Siemens 1PH8 Simotics M compact synchronous motor with four lithium-ion batteries.

The hybrid maintenance vehicles stand out: The yellow chassis competes with the stylish LED lights for attention. However, not everything is new about the vehicles, reveals Ralph Kessler, CEO at automation specialist Späni Elektro-Mechanik AG, who developed and built the hybrid vehicle together with machine manufacturer Tafag AG: "The undercarriage consists of a former freight car. This was completely restored. We removed one axle of the car and installed a 69-kW Simotics compact synchronous motor instead." An advantage of this solution: The cars are already certified. Complete new development and obtaining all approvals would involve very high costs.

The front car area is occupied by the so-called energy module, an impressive structure that also houses the driver's cab. It contains a 15-kW diesel generator with a particle filter, the Sinamics S120 drive system, the four batteries, the power electronics with two S7 controls for operation and battery management, the entire hydraulics as well as the brake pneumatics.

The components outside the heatable energy module are designed in "Siplus extreme" for particularly harsh environmental conditions: Mechanical, chemical or biological stress, condensation and temperatures down to minus 25 degrees cannot harm the components.

With the lifting platform structure, the vehicle weighs around 37 tons. Thanks to this high weight, the car does not need to be supported, even when the platform, which is up to 14 m high, swings far to the side over two tracks. This work facilitation is appreciated by the maintenance personnel, as overhead line work in the middle of the night and in all weather conditions is often a challenge.

The first trips with the new maintenance vehicles are promising: Kessler estimates that the new diesel engine consumes 50 percent less fuel than the previous one. Today, the combustion engine – if at all – is 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 engine automatically shuts off and the vehicle functions electrically again.