Feature: Power
Figure 1: Mersen provided the suitable DC link capacitor for the InMOVE research project
and reduces development costs for the electric drive components. However, this requires integrated power components with a compact design. The overall concept of the project therefore was to use innovative mechatronic technologies. The specifications required
implementation of an 800V system with a switching frequency of 13.5kHz and a current-carrying capacity of 70-80A. In addition, the equivalent series resistance (ESR) had to be low, to minimise power losses. Other requirements included the capacitors to withstand temperatures up to 125°C, offer long service life and have low production costs. The initial goal was to develop
a temperature-optimised DC link capacitor based on two different dielectrics. To this end, electrolytic and film capacitors were considered, since both can handle high currents and high temperatures. However, tests showed that film capacitors could not meet the project’s requirements, due to their high production costs based on the materials available on the market now.
Different approaches Within the consortium, several general concepts for suitable aluminium electrolytic capacitors were then developed, with one main consideration being cooling, since the higher ESR could result in higher power loss and higher temperatures under load.
24 February 2023
www.electronicsworld.co.uk One version consisted of twelve
narrow, long, standard capacitors, whereas another version had flat, wide capacitors. Although Version 1 would have been cheap to make, the probability of failure would have been greater due to the large number of capacitors. In addition, the length of the housing resulted in a poor thermal connection to the cooler, as the design reduced the base cooling surface. Version 2 was based on two capacitors
designed for optimal cooling with a threaded connection – the FTCAP GW
Figure 2: The individual solution for InMOVE is based on the threaded capacitors of the GW series, designed for optimal cooling
series from Mersen. A special stepped base in combination with a Sil-Pad ensures optimal thermal dissipation. The stepped base and a ring clamp allow virtually seamless mounting of the capacitors on a heat sink; see Figure 2. The heavy-duty, laser-welded solid
aluminium housing contributes to a long service life, and an innovative multi-pin cover ensures a low ESR and thus a high current carrying capacity. Although the cover is difficult to manufacture and involved a great deal of development, the consortium settled on Version 2.
Figure 3: During the InMOVE project, Mersen conducted research to determine which electrolytes have a broad temperature range and the required electromechanical properties for the project
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