Feeder to sub feeder rating for drives

[kglade]

I have several variable speed drives mounted in a panel, each on a separate branch circuit. For sizing the feeder to these branches per 430.62, I used the largest rating of the branch circuit short-circuit and ground fault protective device plus the sum of the drive ratings of the other branches. I used the drive ratings instead of the motor loads because of 430.2.

For the feeder that is upstream of this feeder, can I size it the same size as this feeder if there are no other sub feeders? For example, if my feeder per 430.62 is 600A can the upstream feeder be 600A? Or, do I have to keep inflating the next upstream feeder by 125% of its downstream feeder?

-Ken

 

[steve66]

Re: Feeder to sub feeder rating for drives

If I understand your question correctly, the answer would be no. You do not have to keep inflating the feeder size if there are no other loads on it. In essence, if one feeder supplies another feeder and no other loads, they are really considered one feeder, even if there is an additional disconnect or something like that between them.

Steve