I just went through many datasheets of diodes but didn't understand the term "Nonrepetitive Peak Surge Current". Can someone please explain this to me?
In the datasheet of the old 1N4007 we see:
This maximum rating says that these diodes can handle a peak current of up to 30 A during a time of 8.3 ms.
Non-repetitive means that the diode has to "recover" after such a peak. If you repeat such a surge current too soon then the diode may be damaged. What time period is "too soon" and what is "OK" (the diode recovered) is not mentioned. My guess is that if you allow the diode to reach the same temperature that it had before the surge current flowed, it should have recovered. The time needed for that could be one minute or more.
These 1N400x diodes are typically used in bridge rectifiers in power supplies. When the supply is switched on the smoothing capacitor is empty. This causes a large current to flow right after power on. This large current is what this peak current rating is all about (at least for this diode).
In normal use cases the supply is switched on and left on for a while. That allows plenty of time for the diode to recover. That means that the "Non repetitive" isn't much of an issue as switching on the supply doesn't happen so often.