SiC is a key technology for reducing CO2 emissions in railway transportation

PCIM Magazine: From the perspective of a power semiconductor manufacturer: power from overhead lines, power from batteries, or power from fuel cells or hydrogen—are there differences in the circuit design concepts? As a power semiconductor specialist, do you prefer one of these four power supply types, and if so, why?

Jean-Sébastien Straetmans: From a high-level block diagram perspective, a rolling stock electrical architecture can be divided into a traction system and an auxiliary system.

In a DC architecture, the traction system typically consists of an input filter between the catenary and the DC link, followed by an inverter that connects the DC link to the traction motor. In an AC architecture, the input filter is replaced by a transformer and a line-side converter upstream of the DC link.

In hybrid architectures, such as those using batteries or fuel cells, the main difference compared to an AC architecture is that the battery or fuel cell is connected to the DC link via a DC/DC converter.

From a power semiconductor perspective, these architectures differ mainly in topology and voltage levels rather than in fundamental design principles. Infineon offers a broad portfolio of power semiconductor solutions that support all architectures and designs, for both traction and auxiliary systems. This allows us to address the full range of railway power supply concepts without a preference for any single approach.

Rail technology and the 2030 emissions targets. If you compare the current situation with that of 2024, would you say the situation has improved, or rather worsened? What would need to be done to come reasonably close to the emissions targets?

There are currently several large-scale national investment programs aimed at expanding railway infrastructure and accelerating electrification. Examples include China’s 15th Five-Year Plan in combination with the Belt and Road Initiative, India’s Viksit Bharat vision, and major European programs such as Germany’s Deutschlandtakt 2030. A key technology for reducing CO2 emissions in railway transportation is silicon carbide (SiC) power semiconductors. Infineon offers a leading portfolio of SiC modules for both traction and auxiliary systems, supporting the rail industry in making meaningful progress toward emission reduction targets.

For a long time, power semiconductor applications in railway technology primarily relied on silicon-based solutions such as MOSFETs and IGBTs. You are increasingly turning to SiC in railway technology. Given the limited development in the electric vehicle sector, a significant amount of SiC is likely to become available for railway technology. What is the current share of SiC solutions in railway technology, and what do you estimate it will be in 2030?

Silicon carbide needs to be viewed in a broader context. Infineon has made significant investments in SiC technology to address the growing demand driven by decarbonization and digitalization.

Digitalization, particularly through AI and data centers, requires ever higher levels of energy efficiency. At the same time, decarbonization is a central element of global energy policies, and recent energy crises have highlighted the importance of efficient energy use. Decarbonization happens across the entire energy chain. It spans energy generation, for example through sun and wind, energy transmission and distribution through highly efficient grids, and energy consumption. Railway transportation is one part of this energy consumption phase. Silicon carbide has become a critical enabling technology across many sectors, including rail, and its adoption continues to grow on a global scale.

400 V or 800 V? Which power semiconductor architecture is preferred in the railway sector? Would the consistent use of 800 V architectures in railway technology be sensible and forward-looking, or are the planning cycles for such decisions in this sector simply too long, and will 800 V architectures, if at all, only be used in railway technology in a few years?

As already outlined earlier, there is no single preferred voltage architecture from a power semiconductor perspective. Infineon offers a comprehensive portfolio that supports both 400 V and 800 V architectures. Depending on the customer’s system strategy, we can provide solutions optimized for cost efficiency or best-in-class performance. This allows railway system designers to select the voltage architecture that best fits their long-term platform and application requirements.

On-board and off-board. How is Infineon’s business divided between on-board and off-board applications? Or is the use of power semiconductors primarily focused on on-board applications?

Railway investment programs typically include both a rolling stock component and an infrastructure component. Infrastructure covers not only signaling and information management systems, but also the physical rail infrastructure required for passenger and freight transport. In the context of electrification, this includes power infrastructure along the rail network, such as catenary systems and railway substations. Infineon addresses both sides of the equation. We offer power semiconductor solutions for on-board applications in rolling stock, as well as for off-board energy management and signaling systems within the railway infrastructure.

Two years ago, you mentioned that Infineon offers a product portfolio for autonomous driving that is also suitable for rail applications. Have you been able to translate this approach into concrete projects and revenue so far?

Infineon has a broad and scalable semiconductor portfolio that serves automotive applications as well as a wide range of other industries, including railway technology. This puts us in a strong position to support rolling stock manufacturers, regardless of whether their concepts involve conventional operation or autonomous systems. Our approach is technology-driven and platform-based, enabling customers to adapt their designs to different levels of automation as required.

Infineon is in the fortunate position of offering all current types of power semiconductors: silicon, SiC, and GaN. What opportunities do you see for GaN in railway technology? Will vertical GaN be the first to become a major player, or are there also opportunities for lateral GaN?

In lower-voltage applications, such as rolling stock auxiliary systems, designers must balance several factors, including performance, weight and compactness, modularity, and overall cost. Infineon is recognized as a leader in wide-bandgap technologies, including GaN, and we actively support our customers in evaluating these design decisions. At present, the dominant technologies in railway applications remain SiC MOSFETs and silicon IGBTs.

The questions were asked by Engelbert Hopf.