Multiscale Thermal Modelling of Integrated Motor Drives with PCB-Embedded SiC Power Devices

Integrated motor drives are frequently employed in vehicles and aircraft due to their superior power density and efficiency in comparison to separate motors and drives. These advantages are achieved through the tight integration of the electric motor with the power and control electronics within a single housing and cooling system. The latter requires careful design and consideration to ensure safe and reliable operation of both the motor and the power converter. This paper focuses on the thermal analysis of a novel integrated motor drive design, featuring PCB-embedded SiC MOSFETs within a multilevel switching cell array power converter. This architecture avoids the thermal limitations of conventionally packaged power devices. Three multiscale models based on lumped parameter thermal networks, with varying degrees of spatial resolution, are developed. Computational Fluid Dynamics and Finite Element models are employed to evaluate the most relevant heat sources and thermal resistances. Predicted winding temperatures ranged from 106 degrees C to 132 degrees C, all well below the 180 degrees C limit set by the insulation class, underscoring the effectiveness of the proposed design. The overall temperature-corrected electrical efficiency reached 95.4%. The results presented in this work thus highlight the potential of PCB-embedded power devices to improve the integration and thermal management of integrated motor drives. Finally, numerical results from the three multiscale models are compared, highlighting the advantages and limitations of each approach in real-world design scenarios. Among the three thermal models, the simplified single-slot 3D approach provided the best balance between modelling fidelity, computational cost, and development effort.