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Hey, VFD jean yuses

Discussion in 'Commercial' started by flange, Jun 9, 2017.

  1. flange

    flange Act like you care and do SOMETHING!!

    Messages:
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    Location:
    IMT--in my truck
    ok, so the question came up and I cannot find the answer in the ABB manuals. when wiring multiple VFD's, is it acceptable to run the power supplies to say three vfd's in one conduit, then run the load wiring to each motor in separate conduit?

    The book shows conductor sizing based upon cable tray allowing up to nine conductors running together, or three three conductors. obviously with only three cables running together, amp rating is higher ( less heat).
    Can anyone point to a specific section where it says only three conductors per conduit? to me, it should be as directed by the NEC.
     
  2. heavyevans

    heavyevans FNG

    Messages:
    1,258
    Location:
    Indy
    I wouldn't see a problem with it. The problem is when input and output wiring is in the same conduit. The VFD creates it's own sine wave and could put noise back on the system. That wouldn't be an issue in your case.
     
  3. flange

    flange Act like you care and do SOMETHING!!

    Messages:
    12,876
    Location:
    IMT--in my truck

    I have been asked by a client to critique a position put forward by some electrical boy wonder, which if adopted, would cost my client hundreds of thousands of dollars. He quoted page 406 out of the manual, which is effectively a chart for the current ratings of conductors in different configurations, not a limitation on how many. I am sitting here reading this piece of garbage that said engineer wrote and its horrendous. yes, I do realize its 8 pm, its an important client.

    I agree about the output voltage wiring.
     
  4. heavyevans

    heavyevans FNG

    Messages:
    1,258
    Location:
    Indy
    Sorry, my 2ยข had to with drives. NEC is for queers.
     
  5. NZ All Blacks Fan

    NZ All Blacks Fan Just Another swinging Dick

    Messages:
    9,404
    Location:
    West Coast - Canada
    in the Canadian electrical code ( I suspect its close to the American nec) we have a table with the ma conductors in a conduit EG #4 in a 116mm conduit is 86 @ 600V (table 6)
     
  6. crackertech

    crackertech assholiness *

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    Location:
    Fl/IN/Ga/Ms/TX/NJ/VA/NC/TN

    I can't at the last Gig we ran 2-3 per condit ,I agree with heavy on the input output
     
  7. pintofstout

    pintofstout New Member

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    Location:
    Olean, NY
    Guess it would be overly expensive to err on the side of caution?


    Sent from my iPhone using Tapatalk
     
  8. flange

    flange Act like you care and do SOMETHING!!

    Messages:
    12,876
    Location:
    IMT--in my truck
    occupied building, tough to navigate. rewiring feeds on about 16- 25 horsepower VFDS in a 70000 square foot building would be costly. rewiring the output...simple.
     
  9. Joey791

    Joey791 New Member

    Messages:
    45
    Location:
    Louisiana
  10. NZ All Blacks Fan

    NZ All Blacks Fan Just Another swinging Dick

    Messages:
    9,404
    Location:
    West Coast - Canada
    logically speaking - It doesn't make sense to have to have separated motor feeds upstream of the MCC or the VFD - as they are all connected anyways in the distribution panel. the vfd outputs are isolated from the inputs Yes? so why have to separate the inputs?
    I have a friend whom is an electrical engineer I can ask
     
    ReeferPool likes this.