VFD Feeder Size
VFD Feeder Size
(OP)
NEC 2005: Article 430.122(A) states that the feeders of a VFD are required to be sized at 125% of the rated input of the drive. If I don't plan on using the full rating, is there a way around this rule? Why can't I just fuse the input conductors to a smaller size (assuming the conductors can handle the starting current)?
Thanks.
Thanks.





RE: VFD Feeder Size
The problem is that when someone gets a bright idea that they can put a larger motor on the drive, the upstream fuses blow and larger fuses are installed, but the conductor remains the same. Also, the fuses and conductors must be adequately sized to handle whatever output the drive decides to deliver to the motor when it is accelerating.
RE: VFD Feeder Size
The NEC is not just about what you want to do today, but that it is right for whatever someone else who DIDN'T know your original intent may try to do later.