Still a bit unclear on proper spindle grounding

[QuinnSjoblom]

So I have the common 2.2kw spindle and vfd. Plug has 4 wires, I figured out that pins 1 through 3 are for phases but pin 4 is connected to nothing inside the spindle, no ground. How do I do this properly? I have 4 conductor cable with braided sheathing. Should I just run the ground wire to a bolt on my spindle mount instead of the 4th pin? Or open up the top and ground it internally? Also what about the braided sheathing? Ground it at the spindle? Or at the vfd? Or both? Lots of conflicting info out there. What is proper?

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[coherent]

My understanding is, ground the ground wire (the green wire) from VFD ground to the spindle housing or mount if there is not a dedicated ground connection at the spindle. The shielded cable braid should be grounded at only one end... grounded at the VFD, but don't attach it to anything at the spindle end.

[QuinnSjoblom]

My understanding is, ground the ground wire (the green wire) from VFD ground to the spindle housing or mount if there is not a dedicated ground connection at the spindle. The shielded cable braid should be grounded at only one end... grounded at the VFD, but don't attach it to anything at the spindle end.

Yep, that's pretty much what I assumed. Thanks

[mactec54]

So I have the common 2.2kw spindle and vfd. Plug has 4 wires, I figured out that pins 1 through 3 are for phases but pin 4 is connected to nothing inside the spindle, no ground. How do I do this properly? I have 4 conductor cable with braided sheathing. Should I just run the ground wire to a bolt on my spindle mount instead of the 4th pin? Or open up the top and ground it internally? Also what about the braided sheathing? Ground it at the spindle? Or at the vfd? Or both? Lots of conflicting info out there. What is proper?

Remove the top of the spindle is the correct way and connect the # 4 pin inside

The Shield for a VFD to Spindle needs to be Grounded at each end, this is done by folding the shield back and clamping it in the plug cable restraint

There is another way that I have been using, and that is to not use the plug at all and wire direct, using a Cable restraint Gland designed to be used for Shielded Cable, this is much better than using the Plug that come with these spindles

[mactec54]

My understanding is, ground the ground wire (the green wire) from VFD ground to the spindle housing or mount if there is not a dedicated ground connection at the spindle. The shielded cable braid should be grounded at only one end... grounded at the VFD, but don't attach it to anything at the spindle end.

The shield must be Grounded at both ends, at the VFD drive and at the Spindle

[QuinnSjoblom]

Remove the top of the spindle is the correct way and connect the # 4 pin inside

The Shield for a VFD to Spindle needs to be Grounded at each end, this is done by folding the shield back and clamping it in the plug cable restraint

There is another way that I have been using, and that is to not use the plug at all and wire direct, using a Cable restraint Gland designed to be used for Shielded Cable, this is much better than using the Plug that come with these spindles

I've heard from multiple sources that shielding is not supposed to be grounded at both ends for it to shield properly. Is this not true?

[Goemon]

X2 on being confused.

There is conflicting info out there. I saw one YouTube video with a vendor wiring a Chinese VFD to Chinese spindle and not connecting the ground pin at all. I have also seen diagrams showing a ground wire going from the spindle to seperate box labeled "ground" that didn't seem to be on the VFD or the spindle. I have also seen diagrams showing a wire going from VFD ground to spindle ground.

This really shouldn't be confusing. There are 3 wires going from power outlet to VFD and either 3 or 4 going from VFD to spindle. It shouldn't be that hard to write clear instructions aimed at the hobby-level user (which is what Chinese VFDs are sold for), or label all the pins with useful titles instead of meaningless letters.

[mactec54]

I've heard from multiple sources that shielding is not supposed to be grounded at both ends for it to shield properly. Is this not true?

Yes that is not true, they are misinformed, in a lot of counties it is a code requirement when using a VFD Drive

[Al_The_Man]

I've heard from multiple sources that shielding is not supposed to be grounded at both ends for it to shield properly. Is this not true?

This occurred originally with the implementation of relatively low voltage control systems, CNC etc used in conjunction with high voltage machine/spindle control etc.
The concern was that it could encourage ground loops to occur, inducing noise into low voltage cables, since then it has been a recommended practice to implement something called equi-potential bonding, this is ensuring that each part of the machine and motor frames have a earth conductor, preferably sourced from a Star point ground.
This helps ensure that no difference in potential occurs in any part of the machine and allows earthing both ends of shielded cables.
Al.

[mactec54]

X2 on being confused.

There is conflicting info out there. I saw one YouTube video with a vendor wiring a Chinese VFD to Chinese spindle and not connecting the ground pin at all. I have also seen diagrams showing a ground wire going from the spindle to seperate box labeled "ground" that didn't seem to be on the VFD or the spindle. I have also seen diagrams showing a wire going from VFD ground to spindle ground.

This really shouldn't be confusing. There are 3 wires going from power outlet to VFD and either 3 or 4 going from VFD to spindle. It shouldn't be that hard to write clear instructions aimed at the hobby-level user (which is what Chinese VFDs are sold for), or label all the pins with useful titles instead of meaningless letters.

The Chinese are not going to write anything for you, they are only interested in selling what ever they can, good or bad, I'm not sure why there is no electrical code enforcement of the imports from China

This is information in most cases, is a nightmare for Hobby users, that should not be doing high voltage wiring, before anyone writes this kind of information they should look up there Electrical Codes, or consult and industrial Electrician, 3ph power is not something you just mess with, unless you know for sure what you are doing, videos in most cases are very misleading, and unless they are done by a VFD Drive manufacture, (which there are some ) most all others have some miss information in them

The only country in the world that uses 3ph motor without a Ground is China, this is the reason that you see all these low quality Spindles and AC motors coming from China with no Grounding Terminal, the 3 Pin Spindle Plugs and the none connected 4th Pin on the 4 Pin Plug Spindles all have to be corrected before they can be used


Correct Shield termination and Ground is a must even at Hobby level

Cable Shields terminated at one end provide only electrostatic protection against low-frequency, capacitive coupled interference and emission

[QuinnSjoblom]

So if grounding both ends of the sheild, doesn't the 4th conductor in the cable as ground become redundant? Do you still want both the sheild and the wire grounded at both ends?

[ger21]

The shield is not a ground. It's the shields job to contain noise. The ground is there so you don't get killed.

[Goemon]

The Chinese are not going to write anything for you, they are only interested in selling what ever they can, good or bad, I'm not sure why there is no electrical code enforcement of the imports from China

This is information in most cases, is a nightmare for Hobby users, that should not be doing high voltage wiring, before anyone writes this kind of information they should look up there Electrical Codes, or consult and industrial Electrician, 3ph power is not something you just mess with, unless you know for sure what you are doing, videos in most cases are very misleading, and unless they are done by a VFD Drive manufacture, (which there are some ) most all others have some miss information in them

The only country in the world that uses 3ph motor without a Ground is China, this is the reason that you see all these low quality Spindles and AC motors coming from China with no Grounding Terminal, the 3 Pin Spindle Plugs and the none connected 4th Pin on the 4 Pin Plug Spindles all have to be corrected before they can be used


Correct Shield termination and Ground is a must even at Hobby level

Cable Shields terminated at one end provide only electrostatic protection against low-frequency, capacitive coupled interference and emission

Nobody wants to be wiring up high voltage spindles (or anything else) but until somebody comes up with a standard spindle to VFD cable (which they should), they have to if they want to build a CNC machine. It's not realistic to expect that all hobby level users and small shops will hire an industrial electrician to connect their spindle wires. I seriously doubt an industrial electrician would even accept the job. It's hard enough to get a residential electrician to do some wiring for a reasonable price.

I have wired up a bunch of high voltage projects and some that are considerably more dangerous than CNC spindles (like CRT arcade monitors which hold lethal current even when unplugged). I am perfectly capable of following instructions and taking the suggested safety precautions. IMO, where it gets dangerous is when the instructions are wrong or misleading.

This risk is worse for CNC wiring than anything else I have attempted because there are too many people offering conflicting bits of advice. We have no way of knowing who really understands this stuff vs people who are regurgitating innacurate info. Electricity is one area where I like to be 100% before flipping the switch.

It doesn't need to be this hard. With clear, simple and accurate instructions, connecting wires to screw terminals is not a difficult job

[mactec54]

Nobody wants to be wiring up high voltage spindles (or anything else) but until somebody comes up with a standard spindle to VFD cable (which they should), they have to if they want to build a CNC machine. It's not realistic to expect that all hobby level users and small shops will hire an industrial electrician to connect their spindle wires. I seriously doubt an industrial electrician would even accept the job. It's hard enough to get a residential electrician to do some wiring for a reasonable price.

I have wired up a bunch of high voltage projects and some that are considerably more dangerous than CNC spindles (like CRT arcade monitors which hold lethal current even when unplugged). I am perfectly capable of following instructions and taking the suggested safety precautions. IMO, where it gets dangerous is when the instructions are wrong or misleading.

This risk is worse for CNC wiring than anything else I have attempted because there are too many people offering conflicting bits of advice. We have no way of knowing who really understands this stuff vs people who are regurgitating innacurate info. Electricity is one area where I like to be 100% before flipping the switch.

It doesn't need to be this hard. With clear, simple and accurate instructions, connecting wires to screw terminals is not a difficult job

Just last week I was asked to setup / make some cables for VFD drives to Spindles, this is not very difficult to do, if you are uncomfortable in making a simple cable like this then do you think you should be building a machine like this

You will see who's information is correct, by looking it up in the electrical code regulations, they are not easy to understand, still the best place to look to see if you are doing something you should not be doing also, any good professional Video that has been done by the company that manufactures the product, is another good place to look, most you should not look at, as they have many problems that are incorrect examples of wiring Etc, even the pro's don't normally do a 400Hz spindle, just think that a few years ago the Hobby user could not get or use anything other then a hand router

[Al_The_Man]

Nobody wants to be wiring up high voltage spindles (or anything else) but until somebody comes up with a standard spindle to VFD cable (which they should),

Back in the 80's when I started doing CNC retrofits, Mitsubishi, Fanuc etc, these systems all had integrated type spindles, except they were called spindle drives then, not VFD's.
At that time though, VFD's started arriving on the scene for general 3ph induction motor control.There were no defined instructions or any special cable recommended for the VFD to motor.
The cable manufacturers started getting in on the action and the first that I can remember to bring out a specialty cable was Belden.
This is some of their products and instructions.
I made my own.
Al.

[ClintonCarawayCNC]

My understanding is, ground the ground wire (the green wire) from VFD ground to the spindle housing or mount if there is not a dedicated ground connection at the spindle. The shielded cable braid should be grounded at only one end... grounded at the VFD, but don't attach it to anything at the spindle end.

Why would you not ground the wire in the braided shielding
To the ground on the spindle side??? Please answer carefully because I really don't want to have to re-solder my aviation connector.

[Jim Dawson]

Why would you not ground the wire in the braided shielding
To the ground on the spindle side??? Please answer carefully because I really don't want to have to re-solder my aviation connector.

Normally you would only ground the shield braid at one end to prevent ground loops. Most common connection is at the VFD end. You would connect the motor ground wire at both ends.

[mactec54]

Why would you not ground the wire in the braided shielding
To the ground on the spindle side??? Please answer carefully because I really don't want to have to re-solder my aviation connector.

You should not be soldering the shield to anything

A Ground Connection is not somewhere you connect a Shield too, So, Ground wires to there Ground Terminals only

For the spindle Plug Shield, because these plugs are not EMI Shield Grounding plugs, you don't have any choice other than to fold the shield up and clamp it with the Cable restraint clamp no ideal but the only choice you have

The Plug is Grounded through the Body of the Plug and this in turn will Ground the Shield

[mactec54]

Normally you would only ground the shield braid at one end to prevent ground loops. Most common connection is at the VFD end. You would connect the motor ground wire at both ends.

You should not answer questions like this if you don't know the correct way to install a shielded Cable for a VFD Drive

All Shields must be Terminated at both ends, every VFD Drive Manufacture will tell you this, in some countries it is a Code Requirement

You can not create a Ground Loop if everything if correctly Bonded

Do you know what a Ground Loop is ???

[Al_The_Man]

You should not answer questions like this if you don't know the correct way to install a shielded Cable for a VFD Drive
Do you know what a Ground Loop is ???

Jeez Jim, what were you thinking!: