Power Electronics

 

Power electronics is the key component to ensure an efficient and sustainable electric production and consumption. It is used in order to adjust renewable energy sources like wind and solar to the grid frequency as well as to supply the right frequency for the speed control of a drive train. It is used for LED head-lamps, electric cars, wind energy power plant, gas turbine power plants... Exact compliance to the limit temperatures is mandatory in order to avoid thermo-mechanical stresses, which would dramatically shorten the life expectancy of the materials. Efficient cooling is indispensable in order to achieve the highest power density with the least amount of space.

Components and cooling


Surface temperatures in an IGBT casing

The conventional semiconductors like diodes, IGBT- and MOSFET are mostly used as switches combined in compact power modules. There are modules with or without conducting base plates. The power modules are placed in electrical cabinets with other devices like resistors, condensers or inductive components. In order to dissipate the produced heat losses, the power modules are generally installed on common heatsinks. Some heatsinks are designed to function without fan: the free convection flow will evacuate the heat. More efficient heat sinks need however to work with fans. If heat sinks are not enough, the heat can be moved away by a water cooling system or even heat pipes. All these cooling methods can be well calculated with 3D Computational Fluid Dynamics.

The thermal contact to the cooling device occurs with conductive Thermal Interface Materials. For practical cases, it is unclear how the TIM is filled; the resulting thermal resistant is vaguely estimated, which results in a supplementary imprecision of the thermal calculation. The best method is to measure the thermal resistance, complete measurement systems like T3ster can be therefore utilized.

Cooling Calculations

The smallest calculation model includes only the package, if more details are necessary in order to estimate the chip temperatures, then the simulation should be done at board, rack or even room-level.

 


Streamlines through the heat sink of a power module

The cooling of the power electronics is so important that it should be sketched as early as during the concept phase. The 3D-CFD thermal and flow simulation is the ideal tool to precisely analyze the temperature and flow field; hot spots can be localized and eliminated. With relatively little effort, it is possible to obtain fast and effective computational results. These will make viewable optimization potentials which can then be achieved with further thermal simulations.

Streamlines in the enclosure of a frequency converter

News:
The webinar Cooling of a Wind Power Station IGBT  has been recorded. - You will learn: - Why frequency converters need cooling, - Why the thermal resistance of the Thermal Interface Materials matters, -  How to set-up a transient case for low frequencies ...  

News:
Article about E-Cooling in Mai 2017
periodical Engineering Edge
(article on pages 18-19)

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