Feature: Power
Additional tests at the Kiel University of Applied Sciences confirmed, however, that the hotspot temperature in the capacitor does not exceed 110°C when it is installed in a real cooler. As a result, the consortium now has a suitable DC link capacitor to help implement the 80kW drive module.
Figure 4: FTCAP aluminium electrolytic capacitors from Mersen are available in many versions and can be individually adapted for particular applications
Thermally-compatible electrolytes During implementation of the Version 2 capacitors, Mersen first determined what electrolytes were available for an aluminium electrolytic capacitor in the 125°C temperature range. Lab tests showed that whilst one potential 125°C electrolyte was able to withstand the high temperatures, it did not have the required properties of dielectric strength, conductivity and viscosity. In cooperation with the consortium, the company continued its research for a suitable 110°C electrolyte type; see Figure 3. A prototype capacitor had the
necessary mechanical and electrical properties, and delivered the thermal and electric functionalities at the required AC load of 70A. In a current load test, the temperatures were checked simultaneously at specific capacitor positions. In addition, tests were carried out with external temperature control using a Peltier element. To achieve the necessary alternating current of 70A at 13.5kHz, an excitation coil with a power exciter was integrated by means of a coupling coil in a series-resonant circuit consisting of a test capacitor, a resonant
capacitor and a resonant coil. The tests showed that the capacitor is capable of an AC load of 70A. Since temperature control with a
Peltier element can be used only as an initial approximation of the real cooler, temperatures of up to 140°C occurred.
At Mersen Research and development are high on Mersen’s agenda; the company regularly participates in research projects that involve academia and industry; see Figure 5. Currently, we primarily focus on the automotive industry, especially e-mobility, which creates new challenges for DC link capacitors that must be compact yet more powerful, with greater current capacity. Mersen also continues its work on
FTCAP film capacitors and aluminium electrolytic capacitor. Multi-pin capacitors, for example, could create serious competition for the parallel connected axial capacitors with a soldering star that have dominated the market to date.
Figure 5: Mersen regularly participates in research initiatives at the interface between science and industry – the photo shows another DC link capacitor for the H3-Top project
www.electronicsworld.co.uk February 2023 25
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