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Guiding of air flow and positioning
of power semiconductor modules in a 20 kW auxiliary aggregate

Results are created using Coolit, a software product of Daat Research Corp.

Results are created using Coolit, a software product of Daat Research Corp.

When refurbishing trains
space and cooling
boundary parameters
remain the same whereas
the power density is
increased significantly to
fulfill modern
requirements.

Results are created using Coolit, a software product of Daat Research Corp.

Customer requirements

When refurbishing trains space and cooling boundary parameters remain the same whereas the power density is increased significantly to fulfill modern requirements. The task was to supply sufficient cooling to numerous power semiconductor modules on a heat sink with double sided mounting inside a cabinet with unfavorable air inlet and outlet conditions. Air entered the cabinet in front bottom and exited through a side gap on the entire height on the back side of the cabinet.

Our solution

In the initial configuration more than 20 components - diodes, rectifiers, IGBTs and Mosfets with different sizes and power losses - were distributed on each heat sinks base area. Maximum case temperatures of as high as 120°C were reached. The heat sources had to be regrouped according to thermal requirements. The IGBT modules were aligned along the front edge of the heat sink in order to be supplied with cold inlet air. Mosfets and diodes were further down the flow path receiving preheated air. The rectifiers came to be positioned right at the air inlet.

The asymmetric air flow across the cabinet had to be redistributed and the design of the heat sink had to be adapted such that the critical heat sources were all at the same allowed maximum temperature. Air tends to flow straight until it hits a wall where it is redirected. In order to achieve even air flow distribution flow obstructing baffles in 4 distinct areas were installed and adjusted. Furthermore in one area fin length was shortened. Measurements have proven that the critical heat sources were all at the same temperature of below 90°C despite the very asymmetric air flow conditions. Learn more about our thermal design services.

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