Accurate Prediction of Thermal Runaway at Blocking Conditions in Drives Applications

One promising way to increased power densities of IGBTs and higher output currents of modules is to increase the maximum junction temperatures. With higher junction temperatures and with respect to the used load profiles, the impact of leakage current generated during blocking becomes more and more important. An extension of a power-loss calculation framework is proposed. It enables a fast and accurate calculation of temperature-dependent switching, conduction and blocking losses for a single-phase PWM inverter application for various overload profiles, predicting thermal runaway. Numerical implementation of the algorithm is described, and a critical amount of chip leakage current is determined as a function of different thermal heatsink capacitances.