Sustainable Rail Transportation With High Power SiC Modules: Part 1

The process of electrification of railways, though crucial for achieving net-zero climate targets, is nevertheless far from being complete.  Let’s delve into how high-power semiconductor technologies are accelerating the decarbonization of rail transport, making it cleaner, safer, and smarter.

Decarbonization of transportation: Unraveling the global picture

According to the International Energy Agency (IEA), transportation was responsible for 22% of global CO2 emissions in 2022. To achieve a net zero climate target, public transportation needs to change from vehicles powered by fossil fuels to environmentally friendly means of transport, like electrified trains powered by renewable energy.

Fig. 1: Transportation caused ~22% of global CO2 emissions in 2022.

Rail transport’s greenhouse gas emissions are approximately one-fifth of those from air travel – a fraction that further decreases for electrified trains powered by renewable energy. The expansion and electrification of rail infrastructure are therefore essential for cutting CO2 emissions and hitting climate targets.

Fig. 2: Map of the world with length of rail networks and percentage electrified.

Unlike electric cars, electric locomotives have been widely used for over a hundred years. Nevertheless, the process of electrification of railway tracks is far from complete. In fact, global comparison of railway electrification rates reveals significant differences. Taking the lead is India with ~85% railway electrification, followed by Japan, with ~80% share of electrified track. Rapidly catching up is China, which has the world’s largest high-speed rail system, with a ~70% electrification rate. In Europe, ~60 % of railway track is electrified. Meanwhile, the Americas trail behind, with diesel still powering the majority of trains.

Getting on track with a net zero scenario requires the electrification of diesel trains. This can be done by powering the electrified trains via overhead lines or third-rail systems. Where electrification of railway track is not viable, hybrid propulsion trains are needed. These are the trains that, on non-electrified track sections, can be powered from onboard batteries or hydrogen fuel cells. Energy-efficient power semiconductors are at the core of this transition to green railway traction.

Fig. 3: Environmentally friendly means of transport: electrified trains powered by renewable energy.

Optimized power use for every aspect of trains

At Infineon, we take pride in providing energy-efficient and reliable solutions for traction converters in railway transportation. Our power semiconductors contribute to energy savings in multiple parts of the train, wherever there is a need for efficient energy conversion, for example:

• Converting energy from the overhead line to the motor: that is, in the line converter between the overhead line/catenary and the DC-link capacitor, as well as in the motor inverter, between the DC-link capacitor and the train motor
• Transitioning power from the battery or hydrogen fuel cell to the motor: that is, in the DC-DC converter between the battery or hydrogen fuel cell and the DC-link capacitor; and in the motor inverter, between the DC-link capacitor and the train motor
• Powering auxiliary systems like air conditioning, ventilation, and lighting
  

Fig. 4: Simplified schematic of a propulsion system of a battery train.

While energy efficiency is often top-of-mind, trains also need to be able to operate in extreme conditions with demanding mission profiles over service lifetimes of 30 years or more. Harsh climates with freezing temperatures, heat, and humidity, as well as the frequent acceleration and braking required by trains, can cause thermomechanical stress and result in aging. Therefore, in addition to being energy efficient and providing high power density, power semiconductors need to offer high quality and reliability.

New silicon carbide power modules optimized for rail

Infineon is raising the bar in the field of power and technology with its two new 3.3 kV-rated silicon carbide (SiC) modules with robust .XT interconnection technology:

• FF2000UXTR33T2M1: Room temperature on-state resistance of 1.9 mOhm and nominal current rating of 1000 A
• FF2600UXTR33T2M1: Room temperature on-state resistance of 2.5 mOhm and nominal current rating of 750 A

These modules are designed to deliver high power (~1.5 MW) to applications with demanding mission profiles, like railway traction. The key features of the XHP 2 CoolSiC MOSFET — low power losses and high power density — can be directly translated to multiple system benefits: energy-efficiency, system size and weight reduction and audible noise reduction.

Fig. 5: Infineon’s XHP 2 CoolSiC MOSFET 3.3kV with .XT technology.

To find out more about these power modules and how they contribute to the decarbonization of transportation, watch our Mobility Tech Talk.