Health-Monitoring of IGBT power modules using repetitive half-sinusoidal power losses

Abstract:
In view of ever-increasing power densities and harsh operating conditions manufacturers of power electronic systems are demanding concepts to monitor the ageing process of IGBT power-modules in the field. This paper presents a diagnostic concept to identify the thermal resistance from chip to substrate and to monitor its increase due to the gradual delamination of the IGBT chip-solder. For this purpose the IGBTs are operated with repetitive half-sinusoidal power losses and a modified gate driver measures the amplitude DeltaTJ and the minimum temperature TJ,Min of the resulting junction temperature cycles. The focus of this paper is on the implementation of the diagnostic concept within a voltage source inverter of a hybrid transmission. It describes an inverter control strategy to realize the periodic heating current in a regular operating point and without generating any drive torque. Moreover, the additional increase of the temperature cycle amplitude DeltaTJ due to the increased power losses at higher minimum cycle temperatures TJ,Min is investigated. The diagnostic concept is tested with artificially aged power modules and enables a very robust and selective identification of a delaminated chip-solder and a contaminated cooling system with little implementation effort.