Cooling Design of Integrated Motor Drives Using Analytical Thermal Model, Finite Element Analysis, and Computational Fluid Dynamics

Effective cooling system design is one of the biggest challenges in integrated motor drives (IMDs), where power electronics and electric machine are tightly co-packaged. Reducing the power electronics size for a seamless integration increases the thermal impedance of the system, leading to inefficient heat dissipation. This paper presents a cooling system design method for a silicon carbide (SiC) based IMD using a combination of analytical thermal model, finite element analysis (FEA), and computational fluid dynamics (CFD). An analytical thermal model of a 4-layer printed circuit board (PCB) populated with a D2Pak SiC MOSFET has been developed. Based on the information extracted from this analytical thermal model, the PCB 3D model used in the FEA simulations can be substantially simplified, reducing the number of required finite elements and allowing much faster convergence. The developed simplified FEA model has been used to estimate the required PCB-to-ambient heat transfer coefficients for different inverter losses. Finally, a CFD simulation has been used to estimate the required intake airflow to achieve the desired heat transfer coefficient. Experimental measurements of the IMD power electronics temperature demonstrate the effectiveness of this cooling design.