Using a motor load as an example, it seems IGBTs all obviously have a continuous current rating but with nearly any new load introduced while an IGBT is running, there would be an inrush of current. I cannot find any mfg that produces a time/current graph to show the power handling. OR, possibly the continuous rating is absolute max BUT as I understand it, IGBTs are well known for handling inrush well so I have to think there is some extra head room in there.