I am studying VFD troubleshooting. I just wanted to make sure what I was reading was not erroneous. It says VFD overvoltage fault could be caused by low input voltage or voltage sag. I am not an engineer just so you don't expect me to understand highly complex physics.

I guess a motor single-phasing could be argued as a low input voltage problem (just for that affected phase) although it will cause overvoltage in the remaining phases, therefore triggering the drive's overvoltage fault. I can also guess that a low input voltage could cause over-"current" fault. I don't even know if my guesses are right.

Could you explain how low input voltage/sag can cause drive over-voltage fault? Thanks.

 

Must be a typo, a voltage drop or sag may cause an Over-current fault, or under-voltage fault in a VFD.