A German project has developed and manufactured a low-inductance capacitor that, together with a heat sink and housing, forms an integrated mechanical unit. The design uses a narrow, zinc-plated polypropylene film to minimise the internal resistance, reducing power losses by 20 percent in electric vehicles operating at 800V rather than today’s 400V.
The 18mm wide film used for the capacitor is 2.4 μm thick and equipped with a 3 Ω / 37 Ω (wedge-shaped) zinc coating especially for this project. This allows the winding to achieve a capacity of 78.75 µF. Two windings are connected in parallel within one bank which has a capacity of 2x 157.5 µF. For the entire capacitor, which consists of 4 parallel connected banks, this results in a capacity of 2x 630 µF. The internal electrical connections between the windings and the connecting terminals are manufactured primarily from copper sheets.
The H3Top joint research project includes Robert Bosch, Infineon Technologies, Daimler, FTCAP (part of the Mersen group) and the RWTH Aachen University.
“For this application, we developed a DC link capacitor with an extremely low-inductance design and very high current carrying capacity”, said André Tausche, managing director of FTCAP. “But another special feature is that it is an integrated solution. The capacitor is connected directly to the heat sink, which in turn contains all bore holes and mounts for the other electronic components.”
This enables a very compact design and efficient use of the heat sink, which simultaneously cools the semiconductors mounted on top of the integrated unit. “A special feature is the heat sink, which is potted together with the windings to ensure optimal heat dissipation,” said Tausche. This makes it possible to attach the semiconductor modules directly to the heat sink. “The insights gained from the H3Top project will be used beyond the project for other research and development work,” said Tausche.