Sheilding Masso

angelars

AngelArs
I will be adding a VFD to my CNC (tariffs are coming so need to do this fairly soon). I have been reading on the forum about how there is a lot of signal noise and interference that comes from a VFD, which adversely effects the Masso.

What is the best way to shield the Masso from this interference?

Is it usually line noise, or is it radiated noise that comes from the VFD?

If it's radiated noise, would a faraday cage around the Masso help?

The Masso and the VFD electronics will be in separate boxes, several feet from each other. Would moving the VFD electronics further away (6 to 10 feet) help diminish this interference?

Thank you for this information.
 

halfstep

Halfstep
Since you are mounting your VFD in it's own enclosure, you should be fine at 4+ feet away. A steel or aluminum enclosure acts as a faraday cage. But there are a lot of variables to consider when it comes to EMI/RFI like the use of shielded wires, cables and panel plugs and proper grounding to earth. Finding all the shielded components are difficult and time consuming. Large power supplies can be a source for EMI a well but usually doesn't cause enough problems on it's own. But several of them can be enough to cause some problems. What does your enclosure look like now?
 

angelars

AngelArs
Quote from Halfstep on September 12, 2019, 3:14 am

What does your enclosure look like now?

I am custom designing an area for the CNC in my house now. Walls, outlets and base are all pretty much done. The Masso will be built into the wall with a clear plexiglass cover. The torsion box which the CNC will rest on should be completed in a couple of weeks. It sits on a large table which the VFD electronics will be installed inside. I haven't decided where inside the table the VFD will exactly be. I first need to figure out how the water cooling for the VFD needs to be run. From what I've learned so far the VFD and the Masso should be at least 5 feet apart.
 

breezy

Arie
Staff member
@angelars

It's a case of using shielded cables and correctly earthing them. The VFD on its own doesn't radiate EMI because of internal shielding, but the cables connected to it act as antennas if they aren't shielded. So the VFD to motor should be 4 core shielded cable. 3 cores are used for power, the other to earth the motor and the shield is connected only to earth at the VFD. Most VFDs have filters on the input AC so there is no EMI travelling back that way.

Don't know where you obtained the information about having the MASSO and VFD 5 feet apart. I had the MASSO, VFD and the drives for the steppers in the same cabinet (plastic) within inches of each other and had no problems with EMI. The VFD has now been moved out to alongside the cabinet, only because it failed and it was a pain in the !!! to remove, so it could be sent away for repair.

The people on this forum complaining about EMI problems are those running plasma, which is to be expected with a high voltage arc generating heaps of RF radiation.

The other important thing is star point earthing. Bring all the earth connections back to a single common point in your electronics cabinet which is then connected to the building earth. Do not connect any equipment earth points to adjacent equipment and then run to the earth common because this could cause earth loops which will give you problems in the long run.

The same for the MASSO -ve common, return all -ve connections to a common distribution point, again to prevent unwanted current loops.

Regards,

Arie.
 

angelars

AngelArs
Quote from Breezy on September 12, 2019, 8:49 am

Don't know where you obtained the information about having the MASSO and VFD 5 feet apart.

Arie, thanks for all the great information.

Halfstep had mentioned above that 4+ feet should be good. Mine will probably be 5 feet, although now knowing that it can be closer does help.

Will not be running plasma so it helps knowing that was a source of issues.
 

angelars

AngelArs
Quote from Halfstep on September 18, 2019, 4:02 am

The guy's name is Vince and he has some youtube videos

I used to watch his videos all the time. Then I learned that he was giving out bad information about grounding...
 
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