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Why is there a minimum mains short circuit current rating mentioned in ATV680 datasheets? What is the purpose behind it?

The minimum short circuit current is necessary to ensure the protection by the built-in semiconductor fuses. In case of an internal failure (broken IGBT, short circuit in the DC bus, …) the mains MUST be able to deliver a short circuit current which is big enough to break the fuse.
Example (see attached picture):
If an ATV680C16Q4X1 with 400A fuses is supplied by a generator which delivers just 1000A in case of a short circuit, the fuse will take 60 sec (!) to melt. With the recommended minimum short circuit current of 4000A it will take just 2 milliseconds!
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