We are using an hex IGBT module (datasheet: http://www.microsemi.com/document-portal/doc_view/7751-aptgt150ta60pg-rev2-pdf) which is driven by two separate IGBT drivers, the 2SC0108T2D0-07 (datasheet http://www.igbt.cn/UserFiles/CONCEPT/2SC0108T2Dx_Manual.pdf), using two channels on one, one channel on the other module to drive the "bottom" three IGBTs in the module as a DC-DC converter.
During some testing, we had set the current limit too high for the module, and something stopped working. During the de-bug stages, we took the unit apart and discovered that the drivers both had faults. After replacing both drivers, the faults went away, and we could run the circuit to check the IGBTs themselves.
By putting a voltage across each IGBT in turn, we checked that there was no current flowing when the IGBT was stopped, and then that current was flowing when the IGBT was activated again. By this method it looks like all the IGBTs are fully working.
The question is then: how did an over current event knock out both of the IGBT drivers, yet not damage the IGBTs themselves?