Comparison of Cooling Methods for Underground Electric Vehicle Chargers

This paper compares the indirect cooling method using a heatpipe and air-cooled circular fins with conventional cooling methods like forced air convection and forced water convection for cooling power electronics placed underground. A two-module dual active bridge power converter with reconfigurable outputs for electric vehicle charging is used for the thermal analysis. The comparison is based on specific constraints imposed by semiconductor switch surface area requirements and the maximum junction temperature limit. A detailed analysis is presented, and performance parameters like convective resistance, pressure drop, and mechanical pumping power of the cooling systems as the function of volume flow of working fluid are obtained. Commercially available cooling components like extruded fin heatsinks, cold plate, and heat exchanger are used for conventional cooling methods analysis. Whereas indirect cooling using heatpipes and air-cooled circular fins is designed by performing individual analysis on a heatpipe sizing, air-cooled circular fin design, and heatpipe integrated base plate. This work also highlights the equivalent thermal resistance model for each cooling system.