Bächli AG : Swiss Engineering For The Railways Of The Future

Bächli AG develops custom rail boxes for high-performance, standards-compliant, and energy-efficient rail vehicles.

The rail industry faces a deman- ding technical challenge: rail vehicles must be more powerful, more energy-efficient, more com- pact, and reliable over the long term. At the same time, require- ments for safety, compliance with standards, documentation, and system integration are increasing.

Bächli AG addresses these re- quirements with custom, ready- to-install electrical system units. These units not only bring indivi- dual components together but are also developed, tested, and docu- mented as well-designed system solutions.

Bächli AG: Swiss Development Partner for the Rail Industrye

Bächli AG, headquartered in Kriens-Ober- nau, has been developing and manufactu- ring high-quality inductive components and electrical engineering system solutions for over 75 years. Its product range includes transformers, chokes, and filters, as well as integrated assemblies for demanding industrial applications. In railway technolo- gy, this expertise is particularly valuable in situations where standard solutions do not sufficiently meet requirements regarding installation space, weight, thermal beha- vior, interfaces, or documentation.

As a Swiss family-owned company, Bächli integrates engineering, design, manufactu- ring, testing, and documentation through close collaboration. Short lines of commu- nication between development and produc- tion make it possible to resolve technical is- sues early on and incorporate insights from manufacturing directly into the product de- sign. For rail projects with tight timelines, demanding certification requirements, and numerous system interfaces, this close in- tegration is a tangible advantage.

Bächli does not see itself merely as a com- ponent supplier, but rather as a technical development partner. Customers receive support from the initial requirements ana- lysis through feasibility studies and variant analyses all the way to manufacturing, testing, and project documentation. The goal is to develop a solution that functions electrically, can be mechanically integrated, remains thermally stable, and transparent- ly meets the relevant regulatory require- ments.

Bächli Rail Boxes: Compact System Units for Rail Vehiclesäe

A prime example of this systemic ap- proach is the Bächli Rail Box. These are project-specific, ready-to-install electrical assemblies that, depending on the vehicle design, can be integrated onto the roof, in the underfloor area, in the engine room, or as a control cabinet solution. They com- bine electrical components into a compact, tested assembly with clearly defined inter- faces to the vehicle.

Such a Rail Box can incorporate, for example, mains chokes, DC line filters, transformers, connection and protection components, sensors, terminals, cable glands, grounding concepts, as well as cus- tomer-specific electrical and mechanical in- terfaces. The specific configuration always depends on the vehicle, the operating envi- ronment, the electrical system architecture, and the customer’s specifications.

However, the added value lies not merely in combining multiple components within a single housing. What is crucial is that the in- dividual functions are already coordinated electrically, thermally, and mechanically during the engineering phase. This allows for a reduction in the number of interfaces, minimizes the integration effort for the vehicle manufacturer, and enables techni- cal risks to be assessed at an early stage. The customer receives a ready-to-install functional unit that is designed, tested, and documented for the intended application.

The rail boxes are designed to be installed in the vehicle as a pre-assembled plug-in solution. Mechanical mounting points, elec- trical connections, grounding, cable entries, interfaces, and documentation are tailored to the intended installation scenario. The vehicle manufacturer mounts the box in the designated location, connects it to the de- signated interfaces, and receives a tested, ready-to-use assembly. This reduces the integration effort and provides planning certainty.

Engineering Designed with the Application in Mind

Every Bahn-Box project begins with the specific application. The starting point can vary greatly: In some projects, a com- plete specification with defined electrical, mechanical, and regulatory requirements is already available. In other projects, only basic parameters such as voltage le- vel, power, installation space, or vehicle concept are available at the outset. Bächli supports customers in both situations.

If a specification is available, it is techni- cally analyzed, scrutinized, and translated

into a robust product design. If the requi- rements have not yet been fully defined, Bächli works with the customer to deve- lop a well-founded specification proposal. This process takes into account electrical parameters such as voltage, current, fre- quency, power, inductance, losses, and insulation requirements, as well as ther- mal constraints, cooling, protection class, serviceability, weight, mounting, shock and vibration requirements, and relevant rail standards.

The systems are designed for the relevant voltage levels in railway technology. Bächli develops and manufactures railway enclo- sures and high-voltage systems up to 3 kV and can also meet requirements arising from grid conversions or project-specificp

system architectures up to 4 kV. Bächli thus has expertise in the central main systems and the associated peripheral components within the vehicle.

This engineering process is deliberately iterative. The initial constraints give rise to conceptual variants, calculations, 3D de- signs, and integration proposals. Potential trade-offs—such as those between power density, temperature, weight, cost, and ins- tallation space—are evaluated transparent- ly. Before a design freeze, mechanical and thermal evaluations, FEM analyses, manu- facturing feedback, or additional customer reviews can be incorporated. Step by step, this process yields a solution that is techni- cally robust and economically sound.

Technical Integration: Electrically, Thermally, and Mechanically Coordinated

The requirements for a rail box vary signi- ficantly depending on the installation loca- tion. For rooftop installations, low weight, a robust enclosure design, corrosion pro- tection, drainage, protection against envi- ronmental influences, secure mounting, and controlled heat dissipation play a key role. For underground installations, the fo- cus is on mechanical durability, protection against dirt, moisture, splashing water, snow, ice formation, or rockfall, as well as reliable thermal design. In machine rooms or indoor environments, on the other hand, accessibility, airflow, device interfaces, and ease of maintenance are crucial.

Bächli does not consider these require- ments in isolation. Rather, electrical design, thermal behavior, mechanical construction, and manufacturing requirements are eva- luated together. As a result, a line reactor or filter is optimized not only for inductance, current-carrying capacity, and power loss, but also for the installation situation, coo- ling concept, wiring configuration, housing design, and interfaces with the vehicle.

This holistic approach is particularly im- portant in railway technology. A component optimized purely for electrical performance may be disadvantageous in a vehicle if it takes up too much installation space, is difficult to manage thermally, or requires complex mechanical integration. Conver- sely, a compact design must not come at the expense of service life, testability, or compliance with standards. The strength of a Bächli Rail Box lies in its ability to inte- grate these requirements at an early stage and derive a coordinated overall design from them.

Thermal design is a key factor in achieving compact designs. To achieve this, Bächli uses modern cooling technologies, air-ther- mal simulations, and various computational approaches for heat dissipation and airflow. This allows cooling, airflow, installation space, and weight to be optimized together as early as the concept phase. In suitable projects, this can result in assemblies that are up to one-third lighter and, at the same time, significantly more compact than a conventional standard design.

Fan design and temperature control are also integrated into the system design. In- ternal temperature control loops reduce the need for external control measures; EMC-compliant fan technology saves instal- lation space around the drive and supports the integration of the entire drive system. In addition, a fan design with automatic mois- ture separation can help to remove mois- ture in a controlled manner and extend the service life of the system box. The rail boxes are designed for a long service life; depen- ding on the project, a life cycle of up to 40 years can be assumed.

This design contributes significantly to the product’s longevity and safety. Even ex- ceptional operating conditions or fault sce- narios—such as high short-circuit forces, localized winding stresses, or overload situations—are taken into account in the design. The goal is to achieve high product stability and ensure behavior that limits consequential damage and, as far as pos- sible, prevents complete system failure. High inductance linearity and defined tem- perature margins support reliable opera- tion throughout the entire life cycle.

In addition to electrical functionality, mechanical integration is an essential component of product development. Hou- sings, mounts, support frames, mounting points, and connection areas must safely withstand the loads encountered during rail operation throughout their intended service life. These include the unit’s own weight, installation and transport loads, ac- celerations in the longitudinal, transverse, and vertical directions, vibrations, shocks, and localized stresses at bolted joints and welds.

EN 15085 is of particular importance for welded assemblies. Bächli holds the re- levant certification and can incorporate requirements for welding design, manu- facturing, quality assurance, testing, and documentation as early as the develop- ment phase. This is especially relevant for roof-mounted and underfloor solutions, where housings and fasteners are directly exposed to mechanical stresses and envi- ronmental influences.

Depending on project requirements, de- signs are evaluated mathematically, sup- ported by FEM analyses, or validated through structural analyses as well as shock and vibration tests. This involves assessing stresses, deformations, natural frequencies, resonance risks, notch effects, welds, and fastening points. Potential weak points can thus be identified before the design freeze and addressed through design improvements.

Mains chokes and DC-line filters as key functions

Common core components in rail power boxes include mains chokes, line chokes, or DC line filters. They perform key functions in electrical rail systems: They limit current surges, smooth out current waveforms, reduce unwanted mains disturbances, and support the electromagnetic compatibility of the entire system. At the same time, they protect power electronics modules from dynamic loads and contribute to the stable operation of the traction or auxiliary power supply.

Several parameters are critical for the de- sign. Inductance influences the dynamic be- havior of the circuit. The rated current and overload capacity determine the electrical load capacity. Losses, winding temperature, and cooling have a direct impact on efficien- cy, service life, and installation space. The saturation behavior of the magnetic circuit, insulation coordination, mechanical moun- ting, and integration into the vehicle deter- mine whether the component will function reliably in real-world rail operations.

When it comes to such components, Bächli combines many years of experience in the design of inductive components with a broad understanding of how they interact with power electronics, vehicle electrical systems, traction systems, auxiliary sys- tems, and EMC requirements. This enables the development of solutions that are not viewed in isolation, but rather function wit- hin the vehicle’s overall electrical system.

At the heart of many Bächli Rail Boxes units is a transformer, a choke, or a filter. Drawing on their wealth of experience, Bächli engineers use calculation, simu- lation, and design tools to optimize these core components for each specific applica- tion. In doing so, they take a holistic view of the magnetic circuit, windings, insulation, thermal reserves, short-circuit resistance, protection concept, and mechanical inte- gration.

Compliance and Complete Documentation

In the rail industry, in addition to a product’s technical function, providing verifiable evi- dence of that function is also important. Requirements from standards, customer specifications, and certification processes must be accurately implemented and do- cumented. Bächli takes this documentation into account not just at the end of the pro- ject, but already during the design phase.

Bächli AG’s scope of services includes not only development and manufacturing but also testing and verification. Extensive electrical tests are conducted in the com- pany’s in-house testing laboratory and documented on a project-by-project ba- sis. These include routine and type tests, partial discharge tests up to 50 kV, induc- tance measurements at test currents up to 20,000 A, high-voltage tests up to 30,000 V, and insulation resistance measurements up to 100 GΩ.

For external testing, such as shock and vibration tests, environmental testing, or other accredited testing procedures, Bächli collaborates with long-standing testing la- boratory partners. This ensures that the

customer receives a tested and fully docu- mented system solution without having to coordinate the testing and documentation process themselves.

Depending on requirements, project docu- mentation may include drawings, connec- tion and circuit diagrams, bills of mate- rials, test plans, test reports, calculation documents, material and manufacturing records, welding documentation, assem- bly information, as well as project-specific conformity and certification documents. Upon request, it is prepared in the required project language and is part of the technical scope of delivery.

This documentation is not a byproduct but rather part of the technical scope of delivery. It reduces coordination efforts, increases traceability, and provides certainty during subsequent inspections, maintenance work, spare parts processes, or retrofit projects. Especially in international rail projects with many partners and interfaces, complete and consistent documentation is a key contributor to project reliability.

Compact and energy-efficient solutions throughout the entire life cycle

Installation space and weight are among the most important design factors in rail vehicle manufacturing. Electrical compo- nents must deliver high performance in a limited space while remaining thermally manageable, easy to maintain, and durable. In this context, “compact” does not simply mean “smaller,” but rather technically ba- lanced. Performance, losses, temperature, the insulation system, cooling, strength, airflow, and service life must all be consi- dered together.

Energy efficiency is both an economic and a technical factor. Every electrical loss ge- nerates heat, places a strain on adjacent systems, and incurs additional costs over the entire operating life. Low-loss trans- formers, chokes, and filters can reduce the thermal load, ease the burden on cooling systems, and support the availability of the overall system. When considering life-cycle costs, a more efficient design can therefore have a significantly greater impact than simply optimizing acquisition costs.

That is why Bächli develops products with the entire life cycle in mind. This en- compasses the design of new systems as well as replacement solutions, moderni- zations, repairs, and retrofit projects. Exis- ting vehicles often have limited space, yet they must meet today’s requirements for reliability, efficiency, and compliance with standards. This is precisely where the com- bination of component expertise, system knowledge, and flexible manufacturing of- fers a decisive advantage.