Session: 05-03 Advanced Cooling Technologies 2

Paper Number: 97886

97886 - A Three-Face Utilized Heat Sink Design for 3-D Integrated 75 kVA Intelligent Power Stage (IPS) 

Increasing the power density is a major challenge in power electronic converters in areas of Electric Vehicles (EV), residential systems and aerospace. A conventional approach has been to increase the switching frequency by employing Wide Band Gap (WBG) devices such as Silicon Carbide (SiC) and Gallium Nitride (GaN) to reduce the size of passive components and hence increase the power density. However, heat sink also occupies a major portion of the total converter volume as the devices and the power devices are usually placed laterally on one side of the heat sink.

This paper proposes a three-face utilized heat sink design for a 3-D integrated a SiC-based 75 kVA Intelligent Power Stage. The structure enables maximum utilization of the heat sink where three sides of the heat sink are utilized to hold the power devices. For loss estimation from power devices, Model Based Optimization (MBO), an efficiency calculation tool, is designed to the estimated power loss at 75 kVA. The power loss is estimated to be around 1350 W. The heat sink needs to dissipate this power efficiently. To ensure optimum heat flow at maximum power, two cases of three-face utilized heat sinks are explored with different fin design. In case 1, cylindrical holes are considered as in whereas in case 2 normal rectangular fins are employed at the center of the heat sink and grid (combination or vertical and horizontal fins) are used at the sides of the heat sink to spread power from the power boards efficiently. A thermal simulation is performed assuming thermal coefficient equal to 400 W/m2K on the fins.      

By comparing the thermal simulation results for both types of heat sink design, it is evident that the maximum temperature of the heat sink at maximum power delivery of 75 kVA is around 56 °C for both heat sink types. Further, for rectangular fin-based heat sink, the heat is spread uniformly on all sides, whereas for cylindrical hole-based design, heat is concentrated on sides which can degrade thermal performance of the heat sink over time. Hence, the rectangular fin-based design is feasible and proposed. The three-sided cooled design is shown to reduce the heat sink volume by around 40% than single sided cooled approach.

Besides the above parametric studies, we also propose a density-based topology optimization scheme to design efficient heat sink that maximizes the cooling performance by an optimal distribution of the thermal material. The classic tree-like structure is obtained to enhance the convection effect. The performance of the topology-optimized heat sink is numerically simulated and compared with the baseline designs. It is shown that the optimized heat sink provides a considerable improvement in terms of the cooling performance for the 3-D Integrated 75 kVA Intelligent Power Stage (IPS).

Presenting Author: Abdul Basit Mirza Stony Brook University