A simple approach for dynamic junction temperature estimation of IGBTs on PWM operating conditions

Power modules including IGBTs (Insulated Gate Bipolar Transistor) are widely used in motor drivers. For the design optimization of the IGBT modules fitted with motor driving conditions, the IGBT junction temperature and the cooling conditions has become a major issue with the increase of the current density and the demand for downsized modules. Especially, estimation of "worst-case" junction temperature caused by a motor locked condition is necessary prior to the module design. In this paper, we propose a simple approach for dynamic junction temperature behavior of IGBTs PWM (Pulse Width Modulation) inverter modules. The dynamic electrothermal calculations are performed using familiar spreadsheet software. In this approach, the mathematical models of the temperature dependencies of the device losses and quasi-one-dimensional difference equations of thermal conduction were used to estimate the junction temperature of the module. To narrow down many device and module parameters in the initial stage of thermal design of the inverter modules, this proposed approach will be an effective tool.