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  1. #1
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    Question Grounding improvements after adding VFD?

    I have an old CNC machine (K2 KG3925) I’ve been running for years with a router, but having recently upgraded to a 3 phase spindle + VFD I’d like to take the time to improve the wiring (specifically grounding and noise suppression).

    The not-very-good diagram attached below shows the basic layout of the system as it is now.

    The CNC controller PCB is driven by a parallel port connection from the PC, and is powered by a 5VDC line taken from one of the PC’s USB ports (ugly, but that’s how it was delivered).

    The VFD is a Huanyang 2.2kW unit, that was supplied with the spindle.

    In terms of earthing paths, the PC, Controller and VFD are all connected to UK 240V mains (live, earth, and neutral). The controller enclosure is earthed via its mains connection.

    On the CNC machine, there is continuity between the spindle can, all servo motor cans, and the CNC body itself; by virtue of metal-on-metal contact for all parts.

    The first thing I need to do is wire the 4th pin on the spindle connector to the spindle can (as it’s not connected to anything on these cheap Chinese spindles), and then run that line to the earth on the VFD.

    I understand the correct way to do it is to have a 4 core shielded cable (U, V, W plus E), where the E core would go to the spindle 4th pin, and also connect the cable shield to that earth core in the cable at both ends. However, I have some suitably rated 3 core shielded cable to hand. Would it be acceptable to connect the shield to the 4th pin on the spindle, and the earth connector on the VFD, rather than use 4 core cable?

    The above would mean the CNC machine body itself is now earthed, but only by virtue of its continuity to the spindle body. Should I also add a separate earth line between the CNC machine body at the earth point on the VFD? I’m aware that with the spindle installed in the CNC machine that would then create a loop of earth wiring.

    I notice there is no continuity between the three earth (E) points on the VFD, so should I wire the spindle earth (and possible CNC machine body earth) to the left earth point in the VFD on my diagram; so they are definitely connected to the mains earth?

    Finally, what other changes should I make? The encoder and limit switch connections between the CNC machine and the controller use Cat (Ethernet) cables; which I assume will have some degree of protection against noise. None of the mains power leads I’m using have any ferrite beads, and I have no EMI filters - would it be advisable to add some?

  2. #2
    Community Moderator Al_The_Man's Avatar
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    Re: Grounding improvements after adding VFD?

    It is always best to bond the frame of the motor to Earth GND by means of a dedicated conductor, rather than leave it to galvanic conduction through machine/metallic ground.
    The general method is from service ground point, to VFD to motor frame.
    The method used to earth ground all metallic parts of the machine is known as equi-potential bonding and when this is done, the elimination of ground loops etc is virtually eliminated.
    Also best to set up a star point ground system, where all, or most earth points end up connected together.
    Al..
    CNC, Mechatronics Integration and Custom Machine Design

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    Re: Grounding improvements after adding VFD?

    Quote Originally Posted by Al_The_Man View Post
    It is always best to bond the frame of the motor to Earth GND by means of a dedicated conductor, rather than leave it to galvanic conduction through machine/metallic ground.
    The general method is from service ground point, to VFD to motor frame.
    The method used to earth ground all metallic parts of the machine is known as equi-potential bonding and when this is done, the elimination of ground loops etc is virtually eliminated.
    Also best to set up a star point ground system, where all, or most earth points end up connected together.
    Al..
    Thanks. That sounds logical. So if I understand correctly, that means taking an earth lead from CNC machine body to the left earth (E) connection in the VFD on my diagram, and also connecting the earth from the spindle to that same earth point.

    Question is; does the earth line from the spindle to VFD need to be a fourth core, or can I get away with using the shield on a three core cable?

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    Re: Grounding improvements after adding VFD?

    Quote Originally Posted by sploo View Post
    I have an old CNC machine (K2 KG3925) I’ve been running for years with a router, but having recently upgraded to a 3 phase spindle + VFD I’d like to take the time to improve the wiring (specifically grounding and noise suppression).

    The not-very-good diagram attached below shows the basic layout of the system as it is now.

    The CNC controller PCB is driven by a parallel port connection from the PC, and is powered by a 5VDC line taken from one of the PC’s USB ports (ugly, but that’s how it was delivered).

    The VFD is a Huanyang 2.2kW unit, that was supplied with the spindle.

    In terms of earthing paths, the PC, Controller and VFD are all connected to UK 240V mains (live, earth, and neutral). The controller enclosure is earthed via its mains connection.

    On the CNC machine, there is continuity between the spindle can, all servo motor cans, and the CNC body itself; by virtue of metal-on-metal contact for all parts.

    The first thing I need to do is wire the 4th pin on the spindle connector to the spindle can (as it’s not connected to anything on these cheap Chinese spindles), and then run that line to the earth on the VFD.

    I understand the correct way to do it is to have a 4 core shielded cable (U, V, W plus E), where the E core would go to the spindle 4th pin, and also connect the cable shield to that earth core in the cable at both ends. However, I have some suitably rated 3 core shielded cable to hand. Would it be acceptable to connect the shield to the 4th pin on the spindle, and the earth connector on the VFD, rather than use 4 core cable?

    The above would mean the CNC machine body itself is now earthed, but only by virtue of its continuity to the spindle body. Should I also add a separate earth line between the CNC machine body at the earth point on the VFD? I’m aware that with the spindle installed in the CNC machine that would then create a loop of earth wiring.

    I notice there is no continuity between the three earth (E) points on the VFD, so should I wire the spindle earth (and possible CNC machine body earth) to the left earth point in the VFD on my diagram; so they are definitely connected to the mains earth?

    Finally, what other changes should I make? The encoder and limit switch connections between the CNC machine and the controller use Cat (Ethernet) cables; which I assume will have some degree of protection against noise. None of the mains power leads I’m using have any ferrite beads, and I have no EMI filters - would it be advisable to add some?
    The Spindle to VFD drive needs to be one cable the Earth / Ground wire being a separate wire will carry noise everywhere so 4 core shielded cable is required and the shield is connected to the plug body not the Earth / Ground pin

    Yes an EMI Power Filter mounted close to the VFD Drives input power will help with noise also TDK Lambada RSEN-2030L is the ideal filter for your VFD Drive but must be mounted as close as possible to the VFD Drive input power connection
    Mactec54

  5. #5
    Community Moderator Al_The_Man's Avatar
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    Re: Grounding improvements after adding VFD?

    Quote Originally Posted by sploo View Post
    Thanks. That sounds logical. So if I understand correctly, that means taking an earth lead from CNC machine body to the left earth (E) connection in the VFD on my diagram, and also connecting the earth from the spindle to that same earth point.

    Question is; does the earth line from the spindle to VFD need to be a fourth core, or can I get away with using the shield on a three core cable?
    It should be an independent conductor from earth ground point to either the plug ground pin or the frame of the motor itself, which is essentially the same thing. It can either be part of the 4 conductors or a ground conductor ran separately.
    CNC, Mechatronics Integration and Custom Machine Design

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    Re: Grounding improvements after adding VFD?

    Quote Originally Posted by Al_The_Man View Post
    It should be an independent conductor from earth ground point to either the plug ground pin or the frame of the motor itself, which is essentially the same thing. It can either be part of the 4 conductors or a ground conductor ran separately.
    No it can not be run as an independent Ground wire in this case, it needs to be shielded , and part of the 4 core cable
    Mactec54

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    Community Moderator Al_The_Man's Avatar
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    Re: Grounding improvements after adding VFD?

    Quote Originally Posted by mactec54 View Post
    No it can not be run as an independent Ground wire in this case, it needs to be shielded , and part of the 4 core cable
    Just another opinion! What basis?
    There is a lot more likely hood of spurious signals being imposed on a conductor that is ran twisted with hi-current carrying ones.
    The earth GND is best kept away from these if at all possible, this is what can and does cause ground loops!.
    This is why when the 3 separate conductors are used ran as twisted motor power conductors, the earth is kept along side and non twisted, this is the preferred method.
    CNC, Mechatronics Integration and Custom Machine Design

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    Re: Grounding improvements after adding VFD?

    Quote Originally Posted by Al_The_Man View Post
    Just another opinion! What basis?
    There is a lot more likely hood of spurious signals being imposed on a conductor that is ran twisted with hi-current carrying ones.
    The earth GND is best kept away from these if at all possible, this is what can and does cause ground loops!.
    This is why when the 3 separate conductors are used ran as twisted motor power conductors, the earth is kept along side and non twisted, this is the preferred method.
    This is not a 50 Hz 60Hz install which can work with what you are saying, and is definitely not a preferred method my be 50 years ago

    You have not done many if any of these High frequency Spindle installs or you would not be posting this, while the spindle is running Rotor Voltage and Frequency, travels through the Ground conductor , unshielded Ground wire will cause unwanted noise if it is independent, So this is a No for all new installs of the High Frequency Spindles
    Mactec54

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    Re: Grounding improvements after adding VFD?

    Quote Originally Posted by mactec54 View Post
    The Spindle to VFD drive needs to be one cable the Earth / Ground wire being a separate wire will carry noise everywhere so 4 core shielded cable is required and the shield is connected to the plug body not the Earth / Ground pin
    I've attached an image showing the top of my spindle, with the plug disconnected. Just to be clear, by "connected to the plug body" you mean that I should ensure there's continuity between the metal plug at the top of the picture and the outer metal shield in the cable?

    There's no continuity between the plug body and any part of the spindle; so assuming I used a 4 core cable (and ensure the earth pin in the spindle socket is connected to the spindle can) then:

    1. Would I connect the earth core in that 4 core shielded cable to the 50Hz mains earth (the bottom left circled 'E' in the VFD drawing in my original post), or the earth point E to the right of the U, V, W connectors in the VFD?
    2. To what would I connect the cable shield at the VFD end?

    Quote Originally Posted by mactec54 View Post
    Yes an EMI Power Filter mounted close to the VFD Drives input power will help with noise also TDK Lambada RSEN-2030L is the ideal filter for your VFD Drive but must be mounted as close as possible to the VFD Drive input power connection
    Great. I see there are sources where I can get it in the UK. Is there any value to putting one of these in front of the CNC controller too? Inside the controller enclosure the 240VAC mains passes through a transformer (to produce 24VDC), and then goes into a circuit board with a number of capacitors before it goes to the Gecko G320 drives, so perhaps this combination of transformer and caps means a filter would be unnecessary?

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    Re: Grounding improvements after adding VFD?

    ...stay grounded.

    High Voltage can kill.

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    Re: Grounding improvements after adding VFD?

    Quote Originally Posted by sploo View Post
    I've attached an image showing the top of my spindle, with the plug disconnected. Just to be clear, by "connected to the plug body" you mean that I should ensure there's continuity between the metal plug at the top of the picture and the outer metal shield in the cable?

    There's no continuity between the plug body and any part of the spindle; so assuming I used a 4 core cable (and ensure the earth pin in the spindle socket is connected to the spindle can) then:

    1. Would I connect the earth core in that 4 core shielded cable to the 50Hz mains earth (the bottom left circled 'E' in the VFD drawing in my original post), or the earth point E to the right of the U, V, W connectors in the VFD?
    2. To what would I connect the cable shield at the VFD end?



    Great. I see there are sources where I can get it in the UK. Is there any value to putting one of these in front of the CNC controller too? Inside the controller enclosure the 240VAC mains passes through a transformer (to produce 24VDC), and then goes into a circuit board with a number of capacitors before it goes to the Gecko G320 drives, so perhaps this combination of transformer and caps means a filter would be unnecessary?

    This is very common that the 4th is not connected and you have to connect this inside under the cap mot of the air cooled spindle you need to mod the cap where it mounts and attach the 4th pin with the Ground connector one of the snips is a stud that you attach a crimp fitting to and lock it to the spindle body you then mod the plastic cover to clear the crimp fitting nut and washer

    Is your spindle only 3 pin or is it 4 pin ??? if 3 pin it will have to be changed to a 4 pin connecter , these 3 Pin where a China only spindle but people buy them anyway not understanding that 4 pin plug is connector is required

    Yes any power supply can have a EMI Power Filter on the input power, they are not always needed though

    In your cabinet you will have a metal plate that everything is mounted on ( Ground Plane ) you can mount a Bus for all your Ground wires to attach at this point so your input mains power supply Ground /Earth will attach at this point, all other parts of your system that have a Ground / Earth wire or connection will attach to this point

    Do you need to have a shielded cable for the Input Mains Power No it is not normally needed , if you have lots of Shielded Cable then you can put it to use for this cable, the Shield must be correctly terminated or can cause problems

    Grounding the Shields are important for the spindle plug you don't have many choices you can roll it back ( not easy to do ) and clamp it under the cable restraint clamp

    Because your spindle has a plastic cap you will have to mount a Ground wire under the cap and connect it to the 4th pin you will have to mod the cap is mounted to allow for the connection

    A few snips to give you a picture of how you should connect Shields Etc.

    Grounding a Shield is done by using a 360 degree clamp this clamp is attached /fastened to the Ground Plane a saddle can also be used but a 360 degree clamp is better and must be a tight clamp around the Shield
    Mactec54

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    Re: Grounding improvements after adding VFD?

    Quote Originally Posted by mactec54 View Post
    This is very common that the 4th is not connected and you have to connect this inside under the cap mot of the air cooled spindle you need to mod the cap where it mounts and attach the 4th pin with the Ground connector one of the snips is a stud that you attach a crimp fitting to and lock it to the spindle body you then mod the plastic cover to clear the crimp fitting nut and washer

    Is your spindle only 3 pin or is it 4 pin ??? if 3 pin it will have to be changed to a 4 pin connecter , these 3 Pin where a China only spindle but people buy them anyway not understanding that 4 pin plug is connector is required
    Fortunately the spindle does have 4 pins, so I opened it up today and added a lead between that unused 4th pin and a ring connector, that will be held in place by one of the screws used to hold on the plastic cap (I shortened the appropriate "leg" on the underside of the cap so everything seats correctly). The attached image shows what I did. There's now continuity between that 4th pin and the spindle body.

    I've also ordered some shielded 4 core cable and will rewire the spindle plug accordingly.

    Quote Originally Posted by mactec54 View Post
    Yes any power supply can have a EMI Power Filter on the input power, they are not always needed though
    I suppose that adding one to the CNC controller power input isn't doing to cause problems, so it's probably worth having one there too, just in case.

    Quote Originally Posted by mactec54 View Post
    In your cabinet you will have a metal plate that everything is mounted on ( Ground Plane ) you can mount a Bus for all your Ground wires to attach at this point so your input mains power supply Ground /Earth will attach at this point, all other parts of your system that have a Ground / Earth wire or connection will attach to this point
    The metal enclosure of the control box is earthed through the mains line that supplies the controller, but as that's the same mains line as used for the VFD (and indeed the PC) does it matter if the spindle is earthed via the VFD or the control box?

    Quote Originally Posted by mactec54 View Post
    Do you need to have a shielded cable for the Input Mains Power No it is not normally needed , if you have lots of Shielded Cable then you can put it to use for this cable, the Shield must be correctly terminated or can cause problems
    I was considering using the 3 core shielded cable for the mains-to-VFD line; though I'm unsure how the shield would be "correctly terminated"?

    Quote Originally Posted by mactec54 View Post
    Grounding the Shields are important for the spindle plug you don't have many choices you can roll it back ( not easy to do ) and clamp it under the cable restraint clamp
    Agreed. I was thinking the cable restraint clamp would be the way to grip the shield.

    Quote Originally Posted by mactec54 View Post
    Because your spindle has a plastic cap you will have to mount a Ground wire under the cap and connect it to the 4th pin you will have to mod the cap is mounted to allow for the connection
    Ah. OK. So the shield should be connected to the 4th pin (and therefore to the earth core inside the cable), or does the above only apply if I only had a 3 core cable? I assume then that the shield also needs to be clamped appropriately and connected to the earth code at the VFD end?

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    Re: Grounding improvements after adding VFD?

    Quote Originally Posted by sploo View Post
    Fortunately the spindle does have 4 pins, so I opened it up today and added a lead between that unused 4th pin and a ring connector, that will be held in place by one of the screws used to hold on the plastic cap (I shortened the appropriate "leg" on the underside of the cap so everything seats correctly). The attached image shows what I did. There's now continuity between that 4th pin and the spindle body.

    I've also ordered some shielded 4 core cable and will rewire the spindle plug accordingly.



    I suppose that adding one to the CNC controller power input isn't doing to cause problems, so it's probably worth having one there too, just in case.



    The metal enclosure of the control box is earthed through the mains line that supplies the controller, but as that's the same mains line as used for the VFD (and indeed the PC) does it matter if the spindle is earthed via the VFD or the control box?



    I was considering using the 3 core shielded cable for the mains-to-VFD line; though I'm unsure how the shield would be "correctly terminated"?



    Agreed. I was thinking the cable restraint clamp would be the way to grip the shield.



    Ah. OK. So the shield should be connected to the 4th pin (and therefore to the earth core inside the cable), or does the above only apply if I only had a 3 core cable? I assume then that the shield also needs to be clamped appropriately and connected to the earth code at the VFD end?
    No the Shield is only clamped by the cable restraint in your case at the spindle and by a clamp at the other end near the VFD Drive

    Where you have added the Ground wire is correct except you have to lock it in place with a star washer and lock nut so you need a long thread like the snip I posted

    You need to make a Star point Ground By adding a Bus all Ground connect at this one point

    You can not use a 3 core Shielded cable for the Spindle to VFD connection you can get your cable from IGUS CF6-15-04 https://www.igus.com/search?q=CF6-15-04

    Just use stranded wire Twisted to make the input connections to the VFD Drive using shielded cable if not done correctly will cause you more problems
    Mactec54

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    Re: Grounding improvements after adding VFD?

    Quote Originally Posted by mactec54 View Post
    No the Shield is only clamped by the cable restraint in your case at the spindle and by a clamp at the other end near the VFD Drive

    Where you have added the Ground wire is correct except you have to lock it in place with a star washer and lock nut so you need a long thread like the snip I posted

    You need to make a Star point Ground By adding a Bus all Ground connect at this one point

    You can not use a 3 core Shielded cable for the Spindle to VFD connection you can get your cable from IGUS CF6-15-04 https://www.igus.com/search?q=CF6-15-04

    Just use stranded wire Twisted to make the input connections to the VFD Drive using shielded cable if not done correctly will cause you more problems
    OK on the shield. I was going to ask how it helps if it's not grounded, and was wondering if it acts as a Faraday cage. Wiki says it does (https://en.wikipedia.org/wiki/Shielded_cable) but that link also indicates the shield should be grounded... so I'm still a bit confused about the non-grounding of the shield.

    I'll fix the ground connection on the spindle with a star washer as advised.

    I'll definitely use 4 core shielded cable for the spindle to VFD connection - it's already on order.

    No worries on not using shielded cable for the VFD mains input - I'll leave it as it is (well, other than adding an RSEN-2030 filter). On that subject, I've just realised I've ordered the RSEN-2030 not the RSEN-2030L. Looking at the datasheet, the difference is in the leakage current; but from what I can work out the 1.0mA leakage current of the non-L version is legal/safe for fixed machinery, so I guess it'll be OK.

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    Re: Grounding improvements after adding VFD?

    Quote Originally Posted by sploo View Post
    OK on the shield. I was going to ask how it helps if it's not grounded, and was wondering if it acts as a Faraday cage. Wiki says it does (https://en.wikipedia.org/wiki/Shielded_cable) but that link also indicates the shield should be grounded... so I'm still a bit confused about the non-grounding of the shield.

    I'll fix the ground connection on the spindle with a star washer as advised.

    I'll definitely use 4 core shielded cable for the spindle to VFD connection - it's already on order.

    No worries on not using shielded cable for the VFD mains input - I'll leave it as it is (well, other than adding an RSEN-2030 filter). On that subject, I've just realised I've ordered the RSEN-2030 not the RSEN-2030L. Looking at the datasheet, the difference is in the leakage current; but from what I can work out the 1.0mA leakage current of the non-L version is legal/safe for fixed machinery, so I guess it'll be OK.
    You are Grounding the Shield just make sure the complete plug when assembled has continuity to the Spindle body

    The complete plug is Grounded through the body to Ground wire this is normal , in your case because your spindle has a plastic cap you will need to add a Ground jumper from the Ground pin to the plug body ( Under the plug ) then the complete Plug will be Grounded so when you clamp the shield in the cable restraint it will be Grounded also

    With the EMI Filter every bit that can be filtered is why I chose that part number and use them on all VFD Drive installs, this has to be mounted as close as you can to the VFD Drive Twist all your wires where ever you can, do not Twist any Ground wires with the power wires in your case Live and Negative

    You will find the filters are High quality with a low cost compared to other EMI Filters which have exposed connections
    Mactec54

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    Re: Grounding improvements after adding VFD?

    Quote Originally Posted by mactec54 View Post
    You are Grounding the Shield just make sure the complete plug when assembled has continuity to the Spindle body

    The complete plug is Grounded through the body to Ground wire this is normal , in your case because your spindle has a plastic cap you will need to add a Ground jumper from the Ground pin to the plug body ( Under the plug ) then the complete Plug will be Grounded so when you clamp the shield in the cable restraint it will be Grounded also

    With the EMI Filter every bit that can be filtered is why I chose that part number and use them on all VFD Drive installs, this has to be mounted as close as you can to the VFD Drive Twist all your wires where ever you can, do not Twist any Ground wires with the power wires in your case Live and Negative

    You will find the filters are High quality with a low cost compared to other EMI Filters which have exposed connections
    Yes; this a good point: because the socket on the spindle is isolated from the can via the plastic cap it will not be grounded. I'll ensure that's fixed.

    On the subject of the VFD earth points, a bit more investigation tells me that connecting the earth core on the VFD-to-spindle wire to the earth point for the incoming single phase mains is the way to go. At least, based on the wiring diagram at this site (which sells the same VFD): https://www.buildyourcnc.com/item/sp...-spindle-novfd

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    Re: Grounding improvements after adding VFD?

    Quote Originally Posted by sploo View Post
    Yes; this a good point: because the socket on the spindle is isolated from the can via the plastic cap it will not be grounded. I'll ensure that's fixed.

    On the subject of the VFD earth points, a bit more investigation tells me that connecting the earth core on the VFD-to-spindle wire to the earth point for the incoming single phase mains is the way to go. At least, based on the wiring diagram at this site (which sells the same VFD): https://www.buildyourcnc.com/item/sp...-spindle-novfd
    It can be done that way, if you only have one thing in you cabinet that needs a Ground / Earth connection that is why you need a Ground / Earth Bus so all the Grounds connect to that one point ( Star Ground )
    Attached Thumbnails Attached Thumbnails Grounding Bus-1.PNG  
    Mactec54

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    Re: Grounding improvements after adding VFD?

    Quote Originally Posted by mactec54 View Post
    It can be done that way, if you only have one thing in you cabinet that needs a Ground / Earth connection that is why you need a Ground / Earth Bus so all the Grounds connect to that one point ( Star Ground )
    Ref the diagram in my original post in the thread... the CNC controller enclosure itself is grounded, but it's because it takes an IEC C13 connector (live, neutral, earth from the 240VAC mains). It would be possible to strip out the earth line from that incoming connector, and instead wire an earth cable from the CNC controller to the VFD earth terminal (or have all earth wires connected to a ground bus that sits between the CNC controller and the VFD). However, the CNC controller uses a transformer to convert the incoming 240VAC to 24VDC, and the only connections between it (the CNC controller) and the CNC machine are that 24VDC (via the Gecko G320 servo drivers), and a few wires that carry the limit switch and server encoder signals. As such, there's no AC mains connection from the CNC controller to the CNC machine; so I assume (perhaps incorrectly) that it's fine for the CNC controller earth to be separate? Probably the same question for the PC too.

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    Re: Grounding improvements after adding VFD?

    Quote Originally Posted by sploo View Post
    Ref the diagram in my original post in the thread..
    Yes which is incorrect

    First the Mains Power coming in to the cabinet needs a Disconnect at the cabinet and a Ground / Earth Bus connected to the Ground Plane

    From the disconnect it has to go to Circuit Breakers for each device being connected to the Mains Power this would be your Transformer and the VFD Drive Etc.

    For the VFD Drive connection

    MCCB

    EMI Power Filter

    VFD connected to terminals R Live and T Neutral Plus Ground / Earth to the Ground Bus

    No Ground / Earth connections can be separate if so you will have a Ground / Earth loop and lots of noise

    If you don't understand this then you should consult with an industrial Electrician that has done VFD Drive installs
    Mactec54

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    Re: Grounding improvements after adding VFD?

    Quote Originally Posted by mactec54 View Post
    Yes which is incorrect

    First the Mains Power coming in to the cabinet needs a Disconnect at the cabinet and a Ground / Earth Bus connected to the Ground Plane

    From the disconnect it has to go to Circuit Breakers for each device being connected to the Mains Power this would be your Transformer and the VFD Drive Etc.

    For the VFD Drive connection

    MCCB

    EMI Power Filter

    VFD connected to terminals R Live and T Neutral Plus Ground / Earth to the Ground Bus

    No Ground / Earth connections can be separate if so you will have a Ground / Earth loop and lots of noise

    If you don't understand this then you should consult with an industrial Electrician that has done VFD Drive installs
    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.

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