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IndustryArena Forum > CNC Electronics > CNC Machine Related Electronics > Single or separate building circuits for Controller, VFD, PC
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  1. #21
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    Apr 2018
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    131

    Re: Single or separate building circuits for Controller, VFD, PC

    Quote Originally Posted by mactec54 View Post
    How many links do you want, if you are a qualified EE than you would know what method is best for EMI control

    Yes, there is plenty of information if you know what to look for, here is one from EATON but I guess in your eyes they don't know either what is the best practice for EMI control
    Well, you seem to have switched your position!

    Earlier in this thread when the issue of metal conduit came up you said:

    Quote Originally Posted by mactec54 View Post
    If this is in your home, then you should be using PVC Conduit
    And yet the Eaton Wiring Best Practices you quoted above says:

    The best method is to use shielded armored cable on the line and load side of the VFD, connecting all grounds as above.
    "Shielded armored cable" is flexible steel conduit, with a shield added. So now you are agreeing with me that steel/metal conduit offers more EMI protection than PVC conduit!

  2. #22
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    Jan 2005
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    15362

    Re: Single or separate building circuits for Controller, VFD, PC

    Quote Originally Posted by RaderSidetrack View Post
    Well, you seem to have switched your position!

    Earlier in this thread when the issue of metal conduit came up you said:



    And yet the Eaton Wiring Best Practices you quoted above says:



    "Shielded armored cable" is flexible steel conduit, with a shield added. So now you are agreeing with me that steel/metal conduit offers more EMI protection than PVC conduit!
    Nothing has changed, you can interpret it any way you like, you are obvious not qualified to make this statement, the Eaten post clearly states which is the best method to use for VFD Drive installation, I could post a lot of other Manufactures that say the same thing for VFD Drive Installation

    #2 The better method would be to use shielded armor cabled or PVC jacketed shielded cable instead of conduit This is very clear 2 choices offered that are better than conduit

    #3The preferred method of using shielded or armored power cable due to the return path for common mode noise Tells you why this is the best choice. If you don't understand this, then you should not be posting about this subject

    You have to understand and have used all these methods to know what works best for an installation like this.
    Mactec54

  3. #23
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    Apr 2018
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    131

    Re: Single or separate building circuits for Controller, VFD, PC

    Quote Originally Posted by mactec54 View Post
    #3 The preferred method of using shielded or armored power cable due to the return path for common mode noise Tells you why this is the best choice.
    -- vs --

    Quote Originally Posted by mactec54 View Post
    If this is in your home, then you should be using PVC Conduit

    So which one are you now saying that [thread originator] catahoula should use to connect his machine to his garage subpanel?

  4. #24
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    Jan 2005
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    15362

    Re: Single or separate building circuits for Controller, VFD, PC

    Quote Originally Posted by RaderSidetrack View Post

    -- vs --




    So which one are you now saying that [thread originator] catahoula should use to connect his machine to his garage subpanel?
    It would depend how far he is from the Sub-Panel, along the wall or ceiling to a Junction box, from the Electrical Junction Box to the machine cabinet it would have to be flexible, most electricians would run across the rafters / ceiling and drop a flexible cable to the machine Cabinet.

    The mains supply / Sub Panel to his cabinet can be anything he wants to use or what Code requires for his area, this is only a 60Hz supply so is not normally any issue for noise, everything from the cabinet disconnect, is what has to be carefully planned to avoid EMI problems, a Ground Bus Bar is needed, a quality EMI Power Filter for the VFD Drive and for any SMPS is a must, then Shielded Cable for the VFD Drive to the Spindle, with the Shield correctly Terminated, any drive motor cables that may be need to use Shielded cable the same applies correct Shield Termination, any cable pairs in the cabinet should be Twisted this helps to eliminate noise so if you start with a plan this can be a very simple process to build a low EMI trouble free cabinet
    Mactec54

  5. #25
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    Apr 2018
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    131

    Re: Single or separate building circuits for Controller, VFD, PC

    Catahoula, my translation of all that is that mactec54 now saying its OK for you to proceed with your original plan of using grounded metal conduit from your garage subpanel.


    And consider adding a separate circuit for the computer equipment, as mentioned earlier:
    Quote Originally Posted by maxspongebob View Post
    If you are running cable, Run 2 circuits. One 12AWG for a 20 Amp 120VAC and one 10AWG for a 240VAC 30 Amp circuit. You could run the PC and electronics off 120VAC and the VFD off the 240VAC.

  6. #26
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    Jan 2005
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    15362

    Re: Single or separate building circuits for Controller, VFD, PC

    Quote Originally Posted by RaderSidetrack View Post
    Catahoula, my translation of all that is that mactec54 now saying its OK for you to proceed with your original plan of using grounded metal conduit from your garage subpanel.


    And consider adding a separate circuit for the computer equipment, as mentioned earlier:
    He could but that would not be the best choice, so no matter what I say you with no experience is now giving instructions of what he could do.

    No, he would not use or need to use a separate circuit for his PC connection, that's as simple as building that circuit connection into his cabinet, this is the normal way it would be done.

    Because you don't know any better this post, Posted by maxspongebob
    If you are running cable, Run 2 circuits. One 12AWG for a 20 Amp 120VAC and one 10AWG for a 240VAC 30 Amp circuit. You could run the PC and electronics off 120VAC and the VFD off the 240VAC.

    This is a very bad Idea to do this, It is what a true Ground loop looks like, and you never want that to be how you wire a Machine.
    Mactec54

  7. #27
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    Apr 2018
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    131

    Re: Single or separate building circuits for Controller, VFD, PC

    Oh my!

    There are plenty of CNC systems where an ethernet cable is the only connection between the CNC machine and the computer. So now [allegedly] the evil ethernet cable (when the computer is on its own circuit from the breaker panel) is going to result in ground loops! Really???

    While in my opinion, an ethernet cable connection is a better choice for a CNC machine, as Catahoula has not specified (in this thread) how his intended computer is to be set up, there are people using WiFi connections to a CNC machine. And in that case, there is absolutely NO physical connection between the computer and the CNC machine. So how does a separate power circuit for the computer cause a ground loop when there is NO physical connection?

    And then there are systems that are permanently separated, and data etc is transferred by a "sneaker net" (walking a disk or flash drive etc from one device to another). So no physical electrical connection there either.

    My point is that one cannot reasonably make such harsh judgments with the situation as presented in this thread due to incomplete information.

    (group)

  8. #28
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    Re: Single or separate building circuits for Controller, VFD, PC

    Quote Originally Posted by RaderSidetrack View Post
    Oh my!

    There are plenty of CNC systems where an ethernet cable is the only connection between the CNC machine and the computer. So now [allegedly] the evil ethernet cable (when the computer is on its own circuit from the breaker panel) is going to result in ground loops! Really???

    While in my opinion, an ethernet cable connection is a better choice for a CNC machine, as Catahoula has not specified (in this thread) how his intended computer is to be set up, there are people using WiFi connections to a CNC machine. And in that case, there is absolutely NO physical connection between the computer and the CNC machine. So how does a separate power circuit for the computer cause a ground loop when there is NO physical connection?

    And then there are systems that are permanently separated, and data etc is transferred by a "sneaker net" (walking a disk or flash drive etc from one device to another). So no physical electrical connection there either.

    My point is that one cannot reasonably make such harsh judgments with the situation as presented in this thread due to incomplete information.

    (group)

    The Judgment is easy if you understand any very basic electrical installation practices.

    The information is written in the post, that you repeated, of how he suggested it be used, or do you need it emphasized word for word.

    You don't have to be the sharpest pencil, to know that connecting two different AC Power Grounds from different sources to the same piece of equipment is not how it is done, it is much easier to just use one AC Power source, and No Ground loop is created.

    Your Ethernet connection is not creating a Ground loop, or any Grounding related problems, how do you come up with these ridiculous replies they are not related in any way to using (2) independent AC power circuits connected to the same machine
    Mactec54

  9. #29
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    Apr 2018
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    Re: Single or separate building circuits for Controller, VFD, PC

    MODERATOR NOTE:

    Its perfectly fine to post a reply to an earlier comment if you have a different opinion than the earlier post. After all, this is a DISCUSSION forum, and discussion is the whole point of the forum. But that also means civilized discussion, free of insults and name-calling etc. Posting a negative judgement about a member skills/background whose opinion you disagree with is not acceptable behavior. After all, members here are generally relatively anonymous, and you do not really know what their qualifications are. So comments similar to "you are obvious not qualified to make this statement" are out of bounds.

    Think what you like, but what you actually post to the forum needs to meet acceptable standards. Messages and members that do not fall within acceptable standards will find their posts deleted and/or ability to post to the forum restricted.

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