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Daisy Chain Power cable

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usher00

usher00

Electrical
Joined
Jul 7, 2016
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6
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Hi,

i was planning to build a design (see attached picture) in which i was planning to use 4 - 50HP 460/3/60 motor with VFD and daisy chaining the incoming power cable. i was wondering if this meets the NEC/IEEE code. Each VFD has a fused disconnect of 100A and i was planning to use #1AWG cable all over.

would really appreciate some input on this.

Thanks

 
 http://files.engineering.com/getfile.aspx?folder=b3726829-33dc-4b00-a858-8dccd8f4ec35&file=47373.jpg
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What's the power draw of each VFD? 1AWG cable is rated for something like 100A (too lazy to look up)? If so, four inverters are sure to overload that one wire.

Dan - Owner
URL]
 
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the amp draw is about 65A per VFD. the rating for #1 is around 130A. i can go with the 300MCM(285A) which would be enough to carry current for all 4 vfds but the vfd lugs doesnt support wire sizes larger then 1/0(150A).
 
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One issue with daisy chains like that is that obviously the first cable must carry the current of all 4 drives. This means it won't fit the terminals on the drives and the strain of such a large cable can even break off lugs. You could use the drive cabinet as an enclosure for a terminal strip or something where you can reduce down to the correct wire size.
 
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The Canadian Code is similar to the NEC.
Depending on the AHJ's interpretation and whether you must add 20% of the largest load you may need 4/0 AWG or as large as 300 MCM cable.
Terminal lugs are approved for the connection of one conductor. They are not approved for joining conductors..
Consider a bus splitter ahead of the VFDs.
You may need a master switch to comply with OHSA regulations.
Realistically, you may need a disconnect switch for each VFD.
Operations may not like the idea of one master switch taking the skid down to service just one pump or VFD.
Yes I agree, the Canadian code does not apply, but when you are this far from compliance with the CEC, you are probably in violation of the NEC also.

Bill
--------------------
"Why not the best?"
Jimmy Carter
 
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Also, does the 65A/per take into account surge currents? I'm going to assume the VFDs are appropriately set up to soft-start such a large load, but without knowing the exact application, I can't necessarily assume...

Dan - Owner
URL]
 
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thanks a lot for your input guys, i am looking into some kind of wire trough underneath the vfds and distribute the wiring with power distribution terminal block. ill update you guys soon :)
 
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