Destruction of a 1.5kA/3.3kV IGBT module when turning off an SC2 short
circuit due to an insufficient driver stage
When selecting an IGBT or IGBTmodule, one has to bear inmind that not all IGBTs are
specified for a short circuit, i.e. their behaviour and robustness during a short is
7.7 Influenceof thestray inductance
7.7.1 Stray inductance in the commutationpath
The stray inductance L
influences the switching behaviour of an IGBT significantly. All
parasitic inductances in the commutation path are combined in the stray inductance.
Therefore, the load inductance is not part of it. Sources of the stray inductance are:
Parasitic inductance of theDC-bus capacitors.
Parasitic inductance of the connection of theDC-bus capacitors to the IGBT or
Internal stray inductance of the IGBT or IGBT module. This comprises of the
parasitic inductance of the connection terminals, the bond wires and a DCB (if
implemented) with copper layer.
What influence the stray inductance will have in particular exemplifying the measuring
During the IGBT turn-onprocess the following applies:
The more L
there is, the more distinct will the drop of the collector-emitter
voltagebewhen the collector current sets in.
The more L
there is, the slower will the collector current rise. Meaning the
same as a reduced
there is, the smaller the turn-on losses E
. In the example o
the turn-on losses with L
70nH are approx. 190mJ. Whereas only
140mJ of switchingenergy occurswithL