Identifying Superimposed Degradation Effects in Power Electronic Modules

Inhalt:
This paper shows how superimposed degradation modes in power electronic modules can be identified separately without explicitly measuring temperature or losses. For this purpose, a method presented in previous work, suitable for the detection of a single aging phenomenon, was extended. The method injects a small-signal ac voltage to the gate-source voltage vGS of a SiC MOSFET to modulate periodic losses, measures the drain-source voltage vDS, and extracts the phase shift between vGS and vDS. The phase shift includes information of the thermal impedance Zth(jomega) and thus changes at distinctive bandwidths for specific degradation modes. This work demonstrates experimentally that this degradation monitoring method is able to separately detect and localize superimposed degradation modes. Experimental results show that the detection and localization of degradation effects is possible with very small loss excitations that are in the range of 1W and for different ambient temperatures.