Thermal stress analysis for IGBT inverter systems

The application of the insulated gate bipolar transistor (IGBT) in medium to high voltage, high current power systems at high switching frequency has increased the need to study the energy loss and the thermal stress of the device. Thermal and thermal stress analyses are essential to optimize the structure and material of the semiconductor module, and to prevent destruction of the devices. In this paper, an electro-thermal IGBT model which can calculate the switching losses over a wide range of working conditions was introduced, and a technique to further increase the simulation speed was explained in detail. To account for the physical geometry of the IGBT modules, a model-order- reduction (MOR) method was used to extract lump-parameter models from finite element (FE) analysis results. The reduced-order thermal model was used together with the IGBT model to simulate accurately both the electrical and the thermal behavior of the semi-conductor device. The current profiles were then imported into the FE simulator to calculate the resulting thermal and thermal stress distribution. To demonstrate the process from system-level simulation to FE thermal stress analysis, a three-phase IGBT inverter system was used as an application example, and some preliminary results were included.