App note: Voltage proof test for metalized film capacitors

App note from Vishay about self recovery of metalized film caps. Link here (PDF)

Voltage proof tests, also called “high pot” tests, are used to check if a capacitor has a breakdown failure mode occurring at a certain test voltage. The detection of breakdown is done by a current detection, specified if exceeding a certain limit (cut off current).
For all capacitor technologies that do not have the ability to recover after a partial breakdown, the current flow is continuous at the moment of a breakdown.
However metalized film capacitors have the property to recover after an instantaneous breakdown (partial breakdown) due to the fact that the metalized electrodes (capacitor plates) act as a fuse. For fusing a small current is needed, but is not continuous.
This effect is defined as “self healing” and not as breakdown.

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