Thermal Characterization Approach for In Situ Estimation of Thermophysical Properties of Magnetic Components of Electric Vehicle Fast Chargers

Abstract

This article presents a cost-effective thermal characterization approach that relies on temperature measurements and numerical simulations to solve an inverse heat transfer (IHT) problem for the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> estimation of thermophysical properties of high-frequency magnetic components. This approach is applied to the magnetic components of a commercial electric vehicle dc fast charger, specifically, to an air-cooled inductor-transformer assembly. Numerical simulations solve a conjugate conduction–convection IHT problem based on surface temperature measurements collected during realistic operating conditions of the charger. These simulations enable rapid <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> estimation of the specific heat capacities, thermal conductivities, volumetric heat generation rates, and convective heat transfer coefficients of the cores and windings of these magnetic components. These estimated properties are then used as inputs in a direct heat transfer (DHT) simulation for the thermal analysis of these components under different cooling conditions, namely natural and forced convection. The thermal analysis of the inductor-transformer assembly shows that active air cooling with forced convection allows sustaining the measured charging power (28.8 kW) up to 6630 s when the surface temperatures of the cores reach the 100 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> C threshold. This charging time is 61.7% longer than that allowed by the passive air cooling at the same charging power.