Fraunhofer IZM’s novel SiC inverter hits 99% efficiency in a 1-liter package for 800 V EV drives

Fraunhofer IZM has unveiled a groundbreaking 500-kW inverter designed for 800 V electric vehicle (EV) drives, achieving a remarkable peak efficiency exceeding 99% within a compact 1-litre package. Developed in collaboration with Mitsubishi Heavy Industries, the inverter delivers 500 A RMS per phase and boasts an exceptionally low effective inductance of around 1 nanohenry, enabling ultra-fast switching speeds of 65 V/ns. This combination of high power density and efficiency represents a significant advancement in inverter technology for high-voltage EV applications. The inverter’s performance is the result of four key engineering innovations. First, the power modules employ a two-level half-bridge topology with twelve silicon carbide (SiC) MOSFETs embedded directly onto the printed circuit board, reducing component height and parasitic inductance. An RC snubber circuit between each module and the DC-link capacitor further suppresses oscillations, allowing the MOSFETs to switch at their physical limits, which reduces losses and cooling demands. Second, the cooling system features a flat, extruded aluminium heat sink with over 40 thin, corrugated channels, optimising heat exchange while maintaining a minimal form factor and keeping production costs low. The third innovation lies in the busbar connections, which are laser-welded directly onto the circuit board, eliminating space-consuming screws and lowering inductance. The vertical arrangement of the input busbars also allows their magnetic fields to partially cancel, further reducing inductance. Lastly, the DC-link capacitors, developed with PolyCharge, use NanoLam technology configured to achieve 2 nH total inductance at 300 microfarads capacitance. Despite higher thermal losses typical of NanoLam capacitors, copper contacts and integration beneath the cooler casing maintain the operating temperature below 130 °C, ensuring reliability. Wiljan Vermeer of Fraunhofer IZM’s Power Electronic Systems group highlighted the design’s efficiency and compactness, noting it surpasses conventional inverter solutions by a factor of five in power density and outperforms leading current systems by 2.5 times. The inverter will be showcased at the upcoming PCIM Europe conference in Nuremberg from 9 to 11 June, where further technical details and potential applications are expected to be discussed. This development marks a significant step forward in the quest for more efficient, compact, and powerful inverters tailored for the next generation of electric vehicles.