2 Attachment(s)
Grounding... That Dark Art
https://www.cnczone.com/forums/attac...d=458552&stc=1
Hi Looking for some help. In the attached PDF is a diagram of my setup. Everything was working fine I had even cut a few jobs on it with no errors. Then yesterday all hell broke loose when I hit run on the VFD the stepper motors went mental and also my keyboard on the PC locked up. So after reading stuff online and watching lots on Youtube as you will have already guessed it must be EMI especially when you consider that not a single cable is a shielded type, Stepper motors or the VFD to Spindle. I have ordered some and will have to wait for it to arrive. Although this will be a major factor it will also be the lack of proper grounding, replacing the the cables with shielded is a task I'm capable of, but my real fear is the grounding. Even in this forum there are lots of conflicting opinions. I would be terrified of making a mistake like a ground loop or mixing AC with DC grounds. So my fellow cnc'rs if someone can look at the PDF I've attached and direct me where to put ground wires on the VFD and Spindle, The CNC chassis or anywhere else they think fit. I would be extremely grateful.
Coco
2 Attachment(s)
Re: Grounding... That Dark Art
Quote:
Originally Posted by
hootsmangreen
https://www.cnczone.com/forums/attac...d=458552&stc=1
Hi Looking for some help. In the attached PDF is a diagram of my setup. Everything was working fine I had even cut a few jobs on it with no errors. Then yesterday all hell broke loose when I hit run on the VFD the stepper motors went mental and also my keyboard on the PC locked up. So after reading stuff online and watching lots on Youtube as you will have already guessed it must be EMI especially when you consider that not a single cable is a shielded type, Stepper motors or the VFD to Spindle. I have ordered some and will have to wait for it to arrive. Although this will be a major factor it will also be the lack of proper grounding, replacing the the cables with shielded is a task I'm capable of, but my real fear is the grounding. Even in this forum there are lots of conflicting opinions. I would be terrified of making a mistake like a ground loop or mixing AC with DC grounds. So my fellow cnc'rs if someone can look at the PDF I've attached and direct me where to put ground wires on the VFD and Spindle, The CNC chassis or anywhere else they think fit. I would be extremely grateful.
Coco
May not be just EMI do you have the correct Shielded Cable from the VFD Drive to the Spindle with the Shield correctly Grounded at each end, is the spindle 4th Pin Grounded to the Spindle body, if not this will have to be corrected by removing the top cap of the Spindle
Dc Com is the return Path for the Dc supply, it is not a Ground
You need to add a Ground Bus or Stud the Ground Plane needs to be Grounded so the input Mains Ground would connect to the Ground Bus and all other Ground need to connect to that ( 1 ) Point ( Star Point Ground ) then any shielded cables then connect direct to the Ground Plane, your Ground Plane is the metal plate that you mount everything on
2 Attachment(s)
Re: Grounding... That Dark Art
See the Siemens paper on equi-potential bonding.
There are generally two schools of though on grounding of power supply commons, I am one who has always Earth grounded the commons of all power supplies where possible. This has served me well as I do not remember any instances of spurious noise problems.
In the past here, it has cured problems of those that had reactions when L.S. tripped etc.
BTW, the E-stop is intended to remove power, not be just an advisory condition.It should be via electro mechanical means. A common mistake with DIY builders.
3 Attachment(s)
Re: Grounding... That Dark Art
Quote:
Originally Posted by
hootsmangreen
Thanks mactec, see right away there is a conflict i understand the gnd from vfd to spindle but after watching corvetteguy50 on YouTube he says only Ground the shielded at one end preferably at the vfd end. But any how your reply has helped so thanks for that. I am getting a bit better understanding of it. But what I was really looking for and I know this is being lazy and/or thick was for someone to draw little circles saying connect wire here and here. Lol
Yes be careful with watching videos the one you mention is not always correct with what he does and how he does it, so you have to make your own assessment when you watch videos and who the person is doing them most are not qualified electrical engineer's or industrial electricians
For VFD wiring just look in any good quality VFD Drive manual they will show you how wires need to be connected and shields are to be Grounded to comply, to find VFD manuals there are many available on line in PDF format
These snips may help with your shield Grounding understanding, I try to keep it simple so most can understand without having to be an engineer what is required to have an almost EMI noise free environment
1 Attachment(s)
Re: Grounding... That Dark Art
Quote:
Originally Posted by
Al_The_Man
There are generally two schools of though on grounding of power supply commons, I am one who has always Earth grounded the commons of all power supplies where possible. This has served me well as I do not remember any instances of spurious noise problems..
If done incorrectly noise is created
No only one school :) doing it the correct way yes commons can be connected to Ground but not normally how most hobby users connect it which is incorrect
The Dc common must first return to the source before going to Ground this is a 2 wire example this is the most common way to do it, but 3 wire can also be used
Re: Grounding... That Dark Art
You have a floating dc 24v output. You need to short the pe terminal and v- terminal. Also where is your field ground coming from? An outlet? You really need a ground rod sank and connect it to the ground buss. Are you using reactors on the input/output side of the VFD?
Re: Grounding... That Dark Art
Quote:
Originally Posted by
MML102783
You have a floating dc 24v output. You need to short the pe terminal and v- terminal. Also where is your field ground coming from? An outlet? You really need a ground rod sank and connect it to the ground buss. Are you using reactors on the input/output side of the VFD?
Every system already has a Ground Rod there is no need to add one, if one was added then it has to be bonded to the Main Power Supply Building Ground Rod
Re: Grounding... That Dark Art
Quote:
Originally Posted by
MML102783
I have watched all of corvetteguys videos and he is not keeping up with information regarding emi. You absolutely don’t want to use a drain wire soldered to a connector then pigtailed to a ground bus.
Correct there are a lot of uneducated people doing incorrect videos to earn money from those that don't no any better
Re: Grounding... That Dark Art
Quote:
Originally Posted by
hootsmangreen
Thanks mactec, see right away there is a conflict i understand the gnd from vfd to spindle but after watching corvetteguy50 on YouTube he says only Ground the shielded at one end preferably at the vfd end. But any how your reply has helped so thanks for that. I am getting a bit better understanding of it. But what I was really looking for and I know this is being lazy and/or thick was for someone to draw little circles saying connect wire here and here. Lol
I just saw something else in your design that may be one of you main problems
Do you have or are you using ( 2 ) different Power outlets to supply your control panel, it looks like you are but can't tell buy your drawing layout
If you are using ( 2 ) different outlets 230v Power sources then you have a Ground loop and this will create all kind of noise problems
