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Maintaining trams and urban railways more efficiently

In collaboration with Bombardier, BENNING has developed a mobile 24 V DC power supply for rail vehicles.

Every day, millions of commuters depend on the reliable and fault-free operation of trams and railways. Technical failures of rolling stock lead to overcrowded stations, congested roads and major delays - which in turn lead to considerable economic loss. Faults are often caused by insufficient or irregular maintenance. A BENNING power supply system reduces the cost of service and repair.

About Bombardier Transportation in Bautzen

In 26 countries 39,700 employees develop and manufacture ingenious rail transportation solutions. The locations in Germany provide sophisticated engineering services and form the backbone of production in Europe.

In Bautzen rolling stock has been built for commuter and intercity trains since 1896, making the works one of the most traditional in the rail industry. Back in the 1930s Dresden's legendary "Großer Hecht" tram was manufactured here.


Bombardier Transportation has developed the plant into a centre of excellence for trams and light rail, which now employs around 1,200 development and production staff on a total area of 300,974 m2. The site is also equipped for static and dynamic tests on rolling stock.

If a single rail vehicle develops problems it usually means that all vehicles of the same type must quickly be checked. This reduces the number of vehicles available and considerably increases the pressure on public transport.

Extreme cost pressures

The current situation in the transportation sector is characterised by significant competition and cost pressures. As a result, considering the rolling stock’s entire lifecycle costs (LCC) has become increasingly important for railway operators. Specifically, the need to save energy and maintenance costs comes into focus. To achieve this, among other things, Bombardier relies on faster and more efficient processes in repair and preventive maintenance as part of normal service intervals. To contribute to the reduction of these costs, vehicle manufacturers like Bombardier provide customers with software-based systems for calculating the LCC, as well as technical solutions that can be integrated into the maintenance processes.

At the Bombardier plant (photo below), the mobile 24V DC power supplies contribute to more efficient maintenance processes every day
At the Bombardier plant (photo below), the mobile 24V DC power supplies contribute to more efficient maintenance processes every day

New design - new requirements

Low-floor vehicles have been designed to improve convenience when entering and exiting trams and trains. As a result, auxiliary systems can no longer be arranged under the carriage body, where they easily were provided with power during servicing. Due to the limited space it can now only be placed on the roof, which makes efficient and safe servicing more difficult to arrange as a continuous power supply to the vehicles must be ensured.

This especially affects the functionality of the brake computers and monitoring devices to be supplied with 24 V DC. Without a parallel coupling, the on-board batteries would run down in a few hours. Due to safety regulations, service and assembly work may not be supplied through the current collector on the vehicle roof in warehouses and depots.

Previous solutions for realisation of the necessary power supply were unwieldy and therefore had considerable potential for optimisation from a time/efficiency viewpoint.

For this reason, BENNING has worked closely with Bombardier in Bautzen on a special charger for supplying power to tram and trains in repair shops, test bays and depots. Key requirements for this project were high mobility, with low weight and components tuned for tough industrial applications, combined with the lowest possible investment costs.

Robust yet mobile and compact housing and the connecting cables are practically sized at 10 m
Robust yet mobile and compact housing and the connecting cables are practically sized at 10 m

Mobile, compact, sturdy

The result was a compact, portable BENNING 24 V charging system that can be connected directly to the on-board batteries. With connecting cables for the battery supply on the right side and a total length of 10 m, the charging system is adequately sized to reach the battery case on the roof of a vehicle without any difficulties.

The necessary AC cord is carried on the left side of the device. Despite all the power cables, the gross weight of the system is only 75 kg and the size remains modest at a height of 1.3 m and a width and depth of 0.6 m. By using fixed castors (forward steerable) it is also highly mobile. The castors are wide enough for it to be safely pulled over railheads with little effort.

For all typical batteries

Nickel-cadmium and VRLA batteries are commonly used in operation. Due to the availability of different battery types and vary- ing numbers of required battery cells, differ- ent charging voltages are necessary, de- pending on the vehicle. BENNING standard components from the TEBECHOP 3000 HDI industry product series are used with a ro- bust housing from the BENNING cabinet range.
The device has a voltage range of 21.6 V to 30.0 V and can cover three predefined charging levels. User-friendly adjustment is via a three-stage selector switch on the front door of the device, enabling user- friendly adjustments. A determined voltage level avoids voltage adjustment confusion. In the first two selection stages nickel-cadmium batteries with 20 cells and a respective charge volt- age of 1.6 V/cell (equalisation charge) and 1.44 V/cell (charge) are supplied. The third charging stage is for the charging behaviour of the lead acid batteries with twelve cells, and a charg- ing voltage of 2.4 V/cell.

Four TEBECHOP HDI modules and the MCU control unit are placed in the upper section of power supply systems.
Four TEBECHOP HDI modules and the MCU control unit are placed in the upper section of power supply systems.

Modular and reliable

To minimise maintenance costs, the unit contains up to four rectifier modules in a 3U hot plug carrier. The modules can be easily replaced during operation - an innovation which significantly reduces the cost of repairs. For a high output capacity the rectifier modules provide an output current of 60 A. When using three modules, symmetrical loading of the supply network is ensured. The sinusoidal current consumption results in only minor repercussions for the supply system. Due to the placement with a maximum of four motor modules, in n + 1 redundancy configuration, the failure of one module only results in minor consequences for the charger’s overall operation, in turn maximising availability and MTBF (mean time between failures).
The use of the vehicle in service does not have to be interrupted. This also applies to outdoor applications, where the BENNING device with protection type IP 65 is used.

High efficiency, low operating costs

The device is characterised by high efficiency and low related operating costs. Even at 25% load, efficiency is over 90%; in the range of 50% to 75% it reaches its maximum of 94%.

User-friendly in every detail

Current and voltage on the output side are displayed via an integrated control and management system (MCU 2500), which also allows the adjustment of corresponding output voltages.
In addition, access via a laptop is provided, enabling quick configuration of the device via the BENNING service software.

Sustainable solutions for the global market

Following the successful introduction of the chargers at Bombardier in Bautzen, various rail operators decided to use the flexible and robust chargers. Currently, talks with railway companies from China and Switzerland are taking place, which are also keen to arrange their service and maintenance processes more efficiently with the help of the BENNING 24 V charging system.

Further information

contact: Gunnar Damaske
telephone: +49 (0) 3 37 08 / 3 18 74

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