I have four variable-frequency drives (VFDs) in total supplied from one largest VFD in system. The other three VFDs don't have connection to ac grid. These three VFDs are supplied from common DC bus.
I don't understand exact reason why I must fuse each inverter DC input. Some documents say it is done for protecting VFD against overloads and some documents say it is for protecting other VFDs in case of short-circuit that may happen in any VFD. Short circuit theory seems logical to me but I can't understand the one says it is against overload since VFD output already protect itself from overloads and there is no connection at the front end of these drives.
What is meant by overload then? (They are supplied by common dc bus only.)
Is there anyone who has comment on it ?