Lifetime Evaluation of IGBT Power Modules Applying a Nonlinear Saturation Voltage Observer

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Lifetime evaluation of IGBT power modules during converter operation requires the on-line measurement of the device temperatures followed by appropriate data compression. Crucial for the temperature measurement is the accurate detection of the current and temperature-dependent on-state voltage of the devices. A solution for this measurement is presented in this paper. The on-state voltage can either be used for direct temperature acquisition or indirectly by calculating the temperature through the power losses and the thermal impedance. Furthermore, the on-state voltage is a means to detect wire bond failures and hence is a feasible parameter for condition monitoring. Since a large amount of data is acquired during operation, appropriate data-compression is implemented which is based on a modified and extended rainflow algorithm.