Abstract
Power Electronic (PE) will play an essential role in future drive concepts. Nowadays, mainly water/glycol-based cooling media are used to cool PE. Due to their high electrical conductivity (EC), water/glycol-based coolants cannot be used for direct cooling of the electrical components. Direct cooling concepts with dedicated transmission fluids show potential usage of fluid in direct contact with electrified parts. This results in special requirements for the fluids and materials. The aimed action as a coolant requires a defined measurement and characterization of fluid properties and heat transfer in order to assess the cooling ability of a fluid. The purpose of the work was to develop a new measurement setup based on the thermal transient method with which the thermal requirements of cooling fluids for a direct cooling concept can be assessed. With this method, relevant transmission fluids have been tested and the thermal performance compared to indirect cooling effect of water/glycol is discussed. The result of the work is that the measurement method is very well suited for the application-related evaluation of the fluids. Direct oil cooling with transmission fluids could increase heat transfer coefficient by a factor of 3 to 8, compared to the indirect cooing with water/glycol as cooling media.
Highlights
The trend in the automotive industry towards electrified powertrain is continuously increasing
Mainly water/glycol-based cooling media are used to cool Power Electronic (PE). Due to their high electrical conductivity (EC), water/glycol-based coolants cannot be used for direct cooling of the electrical components
The state of the art for cooling of PE is the usage of water/glycol-based cooling media. Due to their high electrical conductivity (EC), water/glycol-based coolants cannot be used for direct cooling of the electrical components and is limited in the optimization of heat transfer
Summary
The trend in the automotive industry towards electrified powertrain is continuously increasing. Several ongoing research projects including projects done directly at OEMs show the potential of PE in terms of increasing efficiency in electrified drive trains. One side effect of this goal is the continuously increased heat input, which explains why thermal management becomes more and more important. At starting conditions, relatively high current flows through semiconductors and results in thermal stress which can lead to welding of switch contacts. Direct cooling of the included semiconductors on a PE would reduce the thermal stress and optimize heat transfer
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