With converter topologies in which power semiconductors that are already turned on initially remain currentless and are then supplied with a high di/dt current, a short-term dynamic overvoltage occurs across these semiconductors in the forward direction. If this overvoltage exceeds the desaturation threshold of the driver, the desaturation detector may trigger.
This problem can be corrected by increasing this threshold by the resistance Rth. It should be checked that the response time does not exceed the maximum permissible short-circuit duration for the power semiconductor used.
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