Fraunhofer Institute for Surface Engineering and Thin Films IST
Sensory high-current contact partner with six thin-film sensors for temperature measurement.
Novel front contacts for extremely high power energy transfer
From research
In high-current applications such as e-mobility, temperature monitoring is required by law to prevent damage caused by excessive temperatures and malfunctions during charging. At the same time, it is necessary to modify and coat the contact surfaces in a targeted manner in order to minimize contact resistance and transmit extremely high power. In collaboration with Fraunhofer IVI and Fraunhofer IWU, Fraunhofer IST has developed a thin-film temperature sensor as well as optimized surface pretreatments and customized PVD coating systems for high-current electrical contacts that are specifically designed for use in charging plugs at extremely high power levels.
High-voltage-resistant thin-film sensors on electrical contact partners
A thin-film sensor system was developed to enable reliable temperature measurement at high-current contact points. This was deposited directly onto a high-current contact partner made of electrolytic copper. A thin sensor layer was deposited onto the electrically insulating base layer, which has a high dielectric strength. Six microstructured sensors were positioned on the contact partner: three in close proximity and three at a defined distance from the contact points. This arrangement of the sensors enables high-resolution temperature measurement. Finally, a top layer was applied, which serves both as wear protection and electrical insulation.
PVD coating systems for electrical contacts and optimized contact surfaces
The detachable contact partners in high-current transmission applications must combine excellent electrical conductivity with high wear resistance. In addition, a high surface quality is advantageous for defined contacting. To meet these requirements, a treatment sequence consisting of special surface smoothing and a customized PVD coating system was developed. A bonding layer enables optimum adhesion of the functional layer to the copper contact component. The mechanically adapted contact layer system minimizes contact resistance and thus ensures minimal temperature development in the high-current electrical face contact.
Charging system for e-mobility based on a novel front contact design.
Treated and PVD-coated Cu contacts.
a) Diagram of a thin-film sensor system
b) Diagram of a PVD coating system for high-current electrical contacts
Results and outlook
The results to date show that thin-film sensor technology enables precise temperature measurement in the immediate vicinity of the electrical contact points and that these sensors can therefore be used to monitor the status of the charging plug. In addition, the treated and coated contact components exhibit low contact resistance even after more than a thousand contact cycles in high-current contact. In the future, the sensors and contact coating systems will be tested under real-world conditions in the developed MCS charging plug in order to validate their performance potential. In addition, the aim is to transfer these developments to similar applications such as CCS charging plugs and other high-current electrical applications.
The project
These developments were achieved within the PREPARE project “Novel front contacts for extremely high-power energy transmission” as part of the Fraunhofer Society's internal programs in collaboration with the Fraunhofer Institute for Transportation and Infrastructure Systems IVI and the Fraunhofer Institute for Machine Tools and Forming Technology IWU.