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Feeder sizing on crane, 610

Question asked by kfleming on Apr 17, 2017
Latest reply on Apr 24, 2017 by kfleming

Have the feed for 8 identical gantry motors on a crane.

To start with I used:

Conductor size: 430.24 using largest FLA*1.25 + all other FLA (use table 310.16 with applicable de-rate, and it could run continuously.

Fault protection 430.62 max protection device of one motor + fla of the rest., use table 430.52 to size breaker and can use exception 1 to round up to next standard size.

Section 610.

1) Can now use table 610.14(A) to size the conductor. (select for 60 or 30 min. based on design & de-rate)

2) Is the conductor demand still per 430.24 or 610.14 (E)2, which would be the sum of all 8 motors FLA, (no 125%) ?

3) Fault protection, use 610.41, which is the same method as 430.62.  For feeder fault protection when it's on a crane, does the sizing of the  largest protection device use the same method?  (use table 430.52 & can use exception #1)