what is the different between force reverse recovery and fast reverse recovery in IGBT

 

Early on IGBT had to have a reverse voltage applied to the gate to shut off fast. Newer IGBT have come up with a way to eliminate the need to supply the reverese to shut off. This is called "tail current". Here is a link that desribes it better than I can; http://www.ixyspower.com/images/technical_support/Application%20Notes%20By%20Topic/IGBTs/IXYS_IGBT_Basic_I.pdf

Unless your using an IGBT made quite a while ago, you don't normally have to worry about it.