Is the output of a variable speed drive protected against overloads and short circuits??? Do ordinay devices provide protection or do need to protect the cable that connects the VSD to the electrical motor with fuses and overload relays?
In general, the VFD does provide the protection for the motor circuit down stream, but not up stream. This is not however universal and should be checked out before assuming anything.
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All VFD's must be fuse protected before power enters the VFD, doesn't matter it you are feeding from a power board, MCC, CB Panel. VFD must be protected.
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The VFD and the motor are only protected against motor overloads if the overload parameter in the VFD has been correctly set to the full load current stated on the motor nameplate.
In general, the cable downstream should be no smaller than the cable upstream of the VFD. The primary protection for the cables, VFD and everything else against the risk of short circuit damage remains with the circuit fuses.
Please refer to existing wiring diagrams for similar arrangements as examples of current practice.
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Variable Speed Drives 2
Re: Variable Speed Drives 2
