The thermal management capability of power electronic (PE) systems has a critical impact on the performance and efficiency of electric, fuel cell, or hybrid vehicles. Bus bars, high resistance sensor devices, semiconductor switches, power capacitors are the primary components, which make a major contribution in total heat generation in electrical drive unit. As PE packaging sizes are projected to become smaller, the challenge of managing increased heat dissipation becomes more critical. This paper numerically compares six different cooling strategies to determine the best possible thermal management scenario. A coupled physics co-simulation framework is used to analyze a 35W motor inverter integrated with water cooled heat sink. A multi-physics finite element model, integrating fluid, electrical, and thermal fields, is employed to analyze heat generation within the PE system and the associated cooling mechanisms. The power losses from the inverter system are dynamically computed in 1-D simulation and fed to the multi-physics finite element model as input. The Cooper-Mikic-Yovanovich (CMY) correlation is used to simulate the contact losses between busbar connections. This model considers the effect of surface roughness and topology on the electrical and thermal contact resistances. This research improves the comprehension of optimized cooling techniques, demonstrating the best design with calibrated cooling parameters. Additionally, it presents an effective numerical procedure for analyzing PE cooling phenomena.