Observation of Thermal-Resistance Increase of Degraded IGBT Modules by VCE(sat) Measurement in a Chopper Circuit

Abstract:
This paper presents an observation of the increase in thermal resistance of IGBT modules degraded by power-cycling test. The observation is based on a V(CE(sat)) measurement setup and thermal analysis by a three-dimensional structure model of the module. The V(CE(sat)) measurement setup consists of a sensing circuit and a low-cost IoT platform “Leafony,” which provides the junction temperature T(j) profile of an IGBT chip inside the module. The three-dimensional structure model produces predicted T(j) profile as a bench mark, in which the transient thermal impedance is evaluated by heat transfer analysis. The comparison between the measured and predicted profiles shows increases in thermal resistance in degraded IGBT modules, where two intentionally-degraded modules were created by a power tester. The demonstrated simple platform and T(j) prediction are useful to monitor the health condition on the IGBT modules.