feeder calculation for buss duct with VFD load

[thegreatsparkalini1]

On a ampacity calculation for a machine with a VFD as the largest motor and with combination loads. ... If the FLA and the largest motor HP is marked on the machine nameplate.... Do we rate the wire ampacity to feed the machine as per 430.122A @ 125% of nameplate FLA of entire machine or will other code articles apply?

Is it also correct to size the buss duct and buss duct feeders to 125% of the sum of the FLA's [of the machines on the buss duct] if the machines are likely to run as a "continuous load" [over 3 hours].

Thank you for your advice.

 

[Zifkwong]

I would think that although you are using VFD's you would still need to size the bus for 125% of the largest motor. I can not find any exceptions in the code either.

 

[jim dungar]

430.122(A) says to use 125% of the input to the VFD and does not care about the FLA at all.
430.122(B), which is only applicable if there is a bypass circuit, says to use 125% of the input current or 430.6 which ever is larger