SUMMARY

The advent of increasingly power dense electric motors promises the eventual phasing out of gasoline-powered cars, but EV motors must contend with the thermal constraints of pushing electromechanical limits. Effective motor thermal management solutions must go hand-in-hand with increasing motor power density to address thermal constraints. Traditional cooling technologies such as housing coolant jackets have limitations due to the significant thermal resistance between the motor windings and end windings, and the coolant flow. To address this, several direct cooling solutions for the slot windings have been explored in literature with positive outcomes. Of these, direct winding heat exchangers (DWHX) located inside the slot and adjacent to the slot windings have exhibited greater cooling potential than the traditional housing jacket, by supplying coolant flow close to the windings separated by a dielectric wall. In-slot heat exchangers (HX) inspired by the DWHX concept are being configured for a new 100 kW, 50 kW/L motor design proposed jointly by NREL and ORNL towards the Department of Energy’s U.S. DRIVE program objectives. However, the baseline cooling solution is not optimized to address end winding cooling. Thus, this thesis proposes a modified design for the in-slot heat exchanger that integrates end-winding cooling capabilities with the baseline in-slot cooling. The proposed solution has a 23% higher effective heat transfer coefficient (h_eff) than the baseline with WEG 50/50 as the coolant, and uses the same coolant flow as the baseline HX design while ensuring equally easy integration with the motor. Extending beyond component-level to motor-level analyses, analytical calculations reveal up to a 33% reduction in winding-to-coolant thermal resistance with the proposed design. Meanwhile, FEA and reduced-order motor models show that the proposed design results in a 5.17-5.90 °C reduction in winding and end winding temperatures relative to the baseline.