In addition to providing AC voltage (for example, three-phase 400V AC @  50 Hz) required for the vehicle power system, auxiliary converters also deliver the required battery voltage (for example 110 V DC). To achieve this, they convert the DC voltage provided at the converter input. “They ensure that passengers can charge laptops and smartphones; the air conditioning and ventilation systems are running; and the on-board restaurant can offer hot and cold drinks and food,” Siemens noted. “Without them, connectivity, information or entertainment services on trains would not be available. As part of the system, SiC reduces the overall costs in the on-board electrical system and the energy consumption of the auxiliary converter. It also enables more compact and lighter converter designs, along with a modular and service-friendly design to ensure lower maintenance costs.”

The auxiliary converter makes use of power semiconductors in a half-bridge topology that are based on Infineon’s CoolSiC MOSFET 1200 V technology. Depending on the design, 8 to 16 half-bridge modules are installed for each converter.

Siemens Mobility illustration

The two German companies point to the impetus behind this technology as “the global population experiencing rapid growth, more people around the world moving from the countryside to the city, inner-city challenges posed by the urbanization megatrend, and an increase in the average traveling distance. As a result, the challenges for train systems are also increasing.”

Siemens Mobility uses the new converter on various vehicle platforms. “As a result, the platforms are maintenance-friendly, reliable, economical and, above all, power efficient,” said Dr. Peter Wawer, President of Infineon’s Industrial Power Control Division. “With SiC, we achieve higher switching speed as well as efficiency to reduce the size of transformers, capacitors, cooling elements and the housing unit. The advantages of this semiconductor material are evident and are now being leveraged in rail-bound vehicles.” 

“Our vehicles should not only offer the highest level of passenger comfort but also enable our customers to operate them sustainably over the entire product life cycle,” said Albrecht Neumann, CEO of Rolling Stock at Siemens Mobility. “Energy-efficient on-board power systems can make a major contribution to economical and environmentally-friendly railway operations.” 

According to the IEEE, “Silicon Carbide (SiC) is an emerging semiconductor material that has been widely predicted to be superior to both Si and GaAs in the areas of microwave power devices, power electronic switching devices, high temperature analog and digital electronics, non-volatile memories and UV sensors.”