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Thread: Grounding improvements after adding VFD?

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    Default Re: Grounding improvements after adding VFD?

    Quote Originally Posted by sploo View Post
    I was referring to the original diagram more as context for the question, rather than a statement of correctness.

    .
    Very few actually know what a ground loop is, it is a difference in potential that may exist on earth ground conductors or points of system ground at different points in the system.
    Now in Industrial systems that mix low level and high level high frequency signals, it is advised to use something called equi-potential bonding.
    This is use a dedicated conductor to ground bond each separate metallic parts of a system. Generally ending up at the earthed star ground point
    If this is done properly, it virtually eliminates all chance of ground loops.

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    Default Re: Grounding improvements after adding VFD?

    Quote Originally Posted by sploo View Post
    I was referring to the original diagram more as context for the question, rather than a statement of correctness.

    I suspect that for a home/hobbyist set up, an industrial electrician with VFD experience will be rather hard to find (and expensive); I'm just trying to learn, and get the best/safest wiring I can with the resources available.

    EMI filters are on their way. Shielded cable has arrived today. I've no problem separating out the relevant earth cores in order to use a ground bus, so I'll look into doing that.
    Yes I understand but we seem to be going around and around instead of forward, you are dealing with an industrial device VFD Drive and it has to be treated as such so all wiring must comply it does not matter if it is for a Hobby or a manufacturing plant all electrical wiring needs to comply for your own safety and everyone around you that may come in contact with your machine

    Not all that you see on hobby sites and videos are correct, the basics don't change some are good to look at but not to copy !

    Mactec54


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    Default Re: Grounding improvements after adding VFD?

    Quote Originally Posted by mactec54 View Post
    Yes I understand but we seem to be going around and around instead of forward, you are dealing with an industrial device VFD Drive and it has to be treated as such so all wiring must comply it does not matter if it is for a Hobby or a manufacturing plant all electrical wiring needs to comply for your own safety and everyone around you that may come in contact with your machine

    Not all that you see on hobby sites and videos are correct, the basics don't change some are good to look at but not to copy !
    Two issues really; the first is that I don't have a cabinet/ground bar etc - the machine isn't of that scale, and indeed has been running without problems for ~16 years (albeit with a router rather than a VFD and spindle). Point is: I want to get things clear before I spend time and money; though I've every intention to "do the right thing" (and I appreciate the advice).

    The second issue is mixed information; I mean, even in this thread there's been disagreements. Looking at information regarding the shield on shielded cable (from numerous forums, CNC vendor articles, blog posts, VFD manuals etc) I've learned that:

    • The shield must be mechanically bonded at either end, but absolutely should not be grounded as that's not it's job and how do you expect it to work otherwise
    • The shield absolutely must be grounded at both ends, otherwise how do you expect it to work properly as a shield
    • The shield absolutely must be grounded at one end only, otherwise how do you expect it to work without creating ground loops

    Obviously every source will tell you they're right; but dumb goobers like me have to sift through the "truths" and choose a path. If all the guidance were consistent it'd be easy to move forward.



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    Default Re: Grounding improvements after adding VFD?

    [QUOTE=sploo;2441740]Two issues really; the first is that I don't have a cabinet/ground bar etc - the machine isn't of that scale, and indeed has been running without problems for ~16 years (albeit with a router rather than a VFD and spindle). Point is: I want to get things clear before I spend time and money; though I've every intention to "do the right thing" (and I appreciate the advice).

    Quote Originally Posted by sploo View Post
    The second issue is mixed information; I mean, even in this thread there's been disagreements. Looking at information regarding the shield on shielded cable (from numerous forums, CNC vendor articles, blog posts, VFD manuals etc) I've learned that:
    Mixed information is in most cases the posters are at the same level as you are and are uneducated in what is right and wrong forums can be a bad sources of information as well as losts of posted YouTube videos

    [LIST]
    Quote Originally Posted by sploo View Post
    The shield must be mechanically bonded at either end, but absolutely should not be grounded as that's not it's job and how do you expect it to work otherwise
    Are that would be obvious, with that information the Shield would be doing nothing and not needed this would cause more problems than a cable without a Shield, ( How could you mechanically Bond a Shield without it being Bonded to Ground, Isolated from the Ground Plane ) who ever came up with that idea for a VFD Drive install


    Quote Originally Posted by sploo View Post
    The shield absolutely must be grounded at both ends, otherwise how do you expect it to work properly as a shield
    We are talking about VFD to Motor Cables or any motor to Drive Cables that are Shielded this is Correct


    Quote Originally Posted by sploo View Post
    The shield absolutely must be grounded at one end only, otherwise how do you expect it to work without creating ground loops
    No this is incorrect information, you can not create a Ground loop if Both Ends are Bonded to the same Ground Plane

    Grounding one end only gives you electrostatic protection from low frequency, the noise you want to eliminate is nasty Common Mode Noise

    One End of a Shield is Grounded only for low voltage Analog not AC high voltage high Frequency


    Quote Originally Posted by sploo View Post
    Obviously every source will tell you they're right; but dumb goobers like me have to sift through the "truths" and choose a path. If all the guidance were consistent it'd be easy to move forward.
    And No again you only have to look up a good VFD Drive manufacture and go through there manual they will tell you how to install your VFD Drive, most of what you have been looking at are from people with no experience with VFD Drive installation, especially in a residential setting you have to get it right or your neighbors will be complaining as this can disrupt there power also

    Here are some more snips for you, these are all from manufactures that work to comply with electrical regulations for EMI noise control

    Attached Thumbnails Attached Thumbnails Grounding improvements after adding VFD?-vfd-good-grounding-practice-png   Grounding improvements after adding VFD?-vfd-shield-ground-motor-cable-png   Grounding improvements after adding VFD?-shield-termanation-4-png  
    Last edited by mactec54; 03-24-2021 at 11:35 AM.
    Mactec54


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Grounding improvements after adding VFD?

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Grounding improvements after adding VFD?