IGBT Modules - Technologies, Driver and Application (Second Edition) - page 362

9.2 Short circuit oscillations
Oscillations occurring with short circuits type SC1 need to be differentiated to those of
an SC2 type (chapter
exemplifies the oscillations occurring in
these two operating conditions. During a short circuit SC1 the oscillations shown in the
example occur after a short period of constant short circuit current and can best be seen
in the gate voltage; however, theymay also occur in the collector-emitter voltage or the
collector current, which is not shown here. This is similar in a short circuit SC2.
However, the oscillations there occur during the desaturationphase of the IGBT. Hence,
during the time periodwhen the collector-emitter voltage rises.
Fig. 9.2
Oscillations observed in a short circuit SC1 andSC2
The driving factors if, when and how the oscillations occur aremainly determined by the
construction of themodule, IGBT characteristics aswell as the application conditions.
Shortly after the short circuit
at constant current
During the desaturation
phase of the IGBT
Oscillation frequency 10…20MHz
Influencing factors
Internal module construction
IGBT characteristic
Low junction temperature
Low collector-emitter voltage
High gate-emitter voltage
Internal module construction
IGBT characteristic
Low junction temperature
High collector-emitter
Tab. 9.1
Influencing factors of possible oscillations during short circuits
Usually the manufacturers of IGBTs and IGBT modules conduct tests regarding the
oscillation characteristics during the development phase and implement
countermeasures. Thesemaybe:
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