IGBT Modules - Technologies, Driver and Application (Second Edition) - page 476

Fig. 13.5
Stray inductanceof the construction
Should the construction not allow keeping the switching over-voltages below the
permitted voltage of the semiconductor by design of a low stray inductance and hence
the resulting current gradient, then snubber capacitors may be worth considering
Snubber capacitors are preferably film capacitors of MKP type (Metallised
Polypropylene Capacitor). These capacitors show the ability to self-heal defects in the
Fig. 13.6
IGBTwith snubber capacitors
Basically, a design without a snubber is always preferable, since a snubber adds cost and possibly reduced
longevity of the system.
With a spot-like short circuit between the electrodes the occurring arc vaporises both the dielectric as well as
the metallic film coatings. The reason for the short circuit (defective dielectric) is now eliminated. The arc itself
extinguished caused by the occurring vapour pressure at the punch spot. The holes caused by this process on
the insideof the capacitor reduce the total capacitance onlymarginally.
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