Simulation vs. measurement of transient thermal resistance Zth of power modules and its effect on lifetime prediction

摘要

Simulation and V_(CE)(T)-measurement based Zth are used to calculate the temperature in an IGBT module after short pulse with high peak losses. Temperature gradient shows significant difference and only simulation based Zth agrees well with the test results from short pulses. Delays between switch off of load current and start of measurement in large power modules have a significant impact on the short-time thermal resistance. The influence of the deviation in Zth on the lifetime prediction has been discussed. Depending of inverter output frequency the deviation in short-time thermal resistance influences the calculated temperature ripple and therefore the predicted lifetime. Making use of Finite Elements simulation to determine the transient thermal resistance Zth ensures the correct calculation of short-time thermal behavior for the lifetime prediction.