27 MICROMOBILITY https://www.rutronik.com/ Issue 2 2025 Power Electronics Europe www.power-mag.com For the mobility of tomorrow Traction inverters are crucial for the performance and efficiency of modern electric and hybrid drivetrains. Especially for the increasingly popular micromobility market, they must meet special requirements in terms of their size, weight, efficiency, and costs. Rahul Naik, Field Application Engineer in the Automotive Business Unit (ABU) at Rutronik Micromobility refers to lightweight, often electrically powered, transportation designed for short distances in urban environments. Prime examples include escooters, e-bikes and e-skateboards. Due to their efficiency, comfort, and environmental friendliness, these mobility solutions have become very popular – especially for distances that are too far to walk comfortably but too short for conventional vehicles. The traction inverter is a key component in the drive system of electric vehicles. It converts direct current (DC) from the vehicle battery into alternating current (AC), which powers the electric motor to drive the wheels. The traction inverter also manages the flow of current from the battery to the motor, controlling speed, torque, and regenerative braking. It plays a crucial role in determining the overall performance, efficiency, and responsiveness of the vehicle. Lightweight, compact, and costefficient Micromobility places special demands on traction inverters – they have to be compact, lightweight, and capable of efficiently managing the power needs of the small electric motors. Technological advancements have propelled the development of traction inverters, resulting in smaller, lighter, and more efficient designs. Traditionally, bipolar traction inverters with an insulated control electrode (IGBTs) based on Si technology were used for power conversion. The use of semiconductors with a wide-bandgap offers improvements in terms of efficiency and thermal behavior: Modern materials such as silicon carbide (SiC) and gallium nitride (GaN) enable higher switching frequencies, lower power losses, and greater power density. Additionally, effective cooling methods are necessary to maintain optimal performance and reliability under demanding operating conditions. The challenge of dissipating the heat generated during operation has been solved by advances in thermal management. Reference designing as a team Together with its partner Vishay, the Automotive Business Unit at Rutronik has developed a traction inverter that meets the requirements of 48 V micromobility (Fig. 1). A decisive step was selecting the right components. In addition to current market requirements, the term “micro” also implies size requirements. Besides installation space, factors such as compatibility, heat dissipation, mechanical load, and component life cycle were also considered when selecting the components. The result is a model implementation of a universal traction inverter designed for 48 V electrical systems for drivetrains in lightweight L7e electric vehicles (fourwheeled vehicles with a maximum power output of 15 kW and a maximum speed of more than 45 km/h) and lower. The reference design is based on cutting-edge, high-performance components such as power MOSFETs, TVS diodes, switching diodes and rectifiers, capacitors, resistors, NTC and PTC thermistors, as well as input filters (inductors and EMI filters). The 48 V traction inverter has a continuous power output of 10 kW and a peak power output of 15 kW. The single PCB design reduces the complexity of the overall system. The reference design demonstrates the circuit structure (Fig. 2) and the suitability of the selected components for the application (Table 1). As such, it serves as a customer guide for selecting components when developing a similar charger. Traction inverter offers new opportunities The effects of traction inverter technology extend well beyond individual vehicles, shaping the entire landscape of electric mobility. As electric vehicles become more prevalent, economies of scale and technological advancements will lower the Figure 1: Prototype of the traction inverter (source: Vishay) Figure 2: Printed circuit board of the traction inverter. Upper side with the DC link capacitors MAL218397998E3 (left). The surface-cooled MOSFETs are located on the underside of the PCB. The Power Metal Strip resistors WSLP5931 (right) are located in the center (source: Vishay)
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