240VAC/120VAC service and EMI filter questions


Results 1 to 5 of 5

Thread: 240VAC/120VAC service and EMI filter questions

  1. #1
    Member
    Join Date
    May 2004
    Location
    usa
    Posts
    196
    Downloads
    0
    Uploads
    0

    Default 240VAC/120VAC service and EMI filter questions

    This is more of a code question, I think. I'm putting together the controller box for a 48x48 router and will be running most of the power supplies from 240VAC (nominal). I have my shop wired for 240V/40A with a neutral line as well. I will be using a 240VAC EMI filter for the VFD and a separate one for the electronics cabinet. I plan on an unfiltered power supply for the steppers - maybe 80VDC output with 240VAC input. I will need 120VAC supply for some equipment (power supplies, pumps, fans, lights and such). I expect that draw to be 1-2A max. Dust collector will be supplied from a separate circuit though switched by the controller.

    The questions:
    • Is having 2 EMI filters overkill? Not super expensive so I don't mind and I worry about the VFD "polluting" the stepper PS if they share input power.
    • How much larger should my EMI filter current rating be over the likely draw? I'm thinking at least 20%
    • Is it a US NEC code violation to run a power cord to a distribution box (ie 2 outlets) for 240VAC. I was hoping to put the EMI filters there.
    • Can I take the 120VAC draw from one of the 240 legs and neutral? I know I can but is that US NEC code compliant?
    • Do I need to balance 120VAC draw on both legs of the 240VAC circuit?


    Similar Threads:


  2. #2
    Community Moderator Al_The_Man's Avatar
    Join Date
    Dec 2003
    Location
    Canada
    Posts
    23709
    Downloads
    0
    Uploads
    0

    Default Re: 240VAC/120VAC service and EMI filter questions

    There is no need to 'balance' each 120v circuit.
    You should however have a valid distribution method, not fed from two 120v outlets, you should have an enclosure that distributes the 120- 0 -120v to each of the circuits, properly fused.
    As to EMI filters on the VFD, the VFD has a natural filter immediately the supply enters it, this consists of a 3ph rectifier feeding a very large capacitor bank.
    If using a ordinary 240v 3ph motor, you are better off to put the money into a 3ph choke on the VFD output.
    It is best to consolidate everything in one enclosure rather than a mish-mash of separate devices hooked up.
    BTW, when wiring, it is not code to use a wire gauge that has a larger fuse or protection than the conductor rating.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


  3. #3
    Member
    Join Date
    May 2004
    Location
    usa
    Posts
    196
    Downloads
    0
    Uploads
    0

    Default Re: 240VAC/120VAC service and EMI filter questions

    Thanks, Al. It is a real 240VAC line, not 2 120s.

    I've got this on the way. [edit: fixed link]

    And, yes, no point in using a fuse that doesn't protect the wire.



  4. #4
    Community Moderator Al_The_Man's Avatar
    Join Date
    Dec 2003
    Location
    Canada
    Posts
    23709
    Downloads
    0
    Uploads
    0

    Default Re: 240VAC/120VAC service and EMI filter questions

    Link did not work for me!

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


  5. #5
    Member
    Join Date
    May 2004
    Location
    usa
    Posts
    196
    Downloads
    0
    Uploads
    0

    Default Re: 240VAC/120VAC service and EMI filter questions

    Quote Originally Posted by Al_The_Man View Post
    Link did not work for me!
    works for me but I edited it with a different link, maybe that will work.



Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  


About CNCzone.com

    We are the largest and most active discussion forum for manufacturing industry. The site is 100% free to join and use, so join today!

Follow us on


Our Brands

240VAC/120VAC service and EMI filter questions

240VAC/120VAC service and EMI filter questions

240VAC/120VAC service and EMI filter questions