Wiring HuangYang VFD without grounding! How dangerous is this?

[mactec54]

Thanks skrubol. Good point about not putting a ground between the + and - wires to each motor phase. Your comments suggest it's at least worth wiring up this method to see if it gives good enough suppression.

Since this thread is principally about VFD grounding, can anyone comment on the need to box these chinese VFDs in a metal grounded box. I would imaging the circuitry would be a source of EMI and the plastic box does not even have any sign of conductive paint. It's just plastic. I'm going to box in the stack of stepper driver boards and the ARM controller board but does the VFD need boxing as well?

TIA.

Everything can be in the same Box Cabinet if you do it right

If you have a Plastic Box ( Cabinet ) you add a metal mounting plate inside this then becomes the Ground Plane where you attach a Ground Bar or a Ground Stud, for all your Ground connections ( Star Ground )

You mount everything to this metal plate, which is the Ground Plane

[skrubol]

Everything can be in the same Box Cabinet if you do it right

If you have a Plastic Box ( Cabinet ) you add a metal mounting plate inside this then becomes the Ground Plane where you attach a Ground Bar or a Ground Stud, for all your Ground connections ( Star Ground )

You mount everything to this metal plate, which is the Ground Plane

That doesn't give you any interference protection between stuff in that box. If you need to put some control electronics right next to that unshielded VFD you might see some issues as near-field radiation can be much worse than far-field radiation (far field drops off at the square of distance in open space, near field drops off much quicker usually.) Sticking a piece of grounded sheet metal or some sort of screen between power electronics and instrumentation can even make a big difference.

[reg.miller]

A ground plane is not a Faraday's cage either.

I never intended to put the control electronics in the same enclosure and despite mactec's invitation to "you do it right" , I still don't intend to.

My question is whether I need a metal enclosure around one of these chinese VFDs to stop it polluting my neighbours' homes with EMI.

[Al_The_Man]

I have always place the VFD in the same enclosure as the CNC controller and the rest of the electronics, in one such system I had two VFD's mounted at one side of the common enclosure, one above the other!.
Al.

[reg.miller]

Al, I seem to recall you posting that most of your work was on converting manual machines to CNC. What sort of controllers does that invovle? Are they themselves in a metallic enclosure or bare boards?

[mactec54]

A ground plane is not a Faraday's cage either.

I never intended to put the control electronics in the same enclosure and despite mactec's invitation to "you do it right" , I still don't intend to.

My question is whether I need a metal enclosure around one of these chinese VFDs to stop it polluting my neighbours' homes with EMI.

Nobody needs a Faraday cage, just good wiring practice, and your VFD Drive will not emit any EMI / EMF to bother anything around it, when using a input line filter and shield cables and correct Ground Bonding of shields and Ground wires

Why did you ask, if you where going to do what ever craziness you have in your mind any way, I told you how it is done for a normal installation's, if done right (1 ) Cabinet will be better than ( 2 ) separate Cabinets, I guess you are a conspiracy expert as well

[mactec54]

That doesn't give you any interference protection between stuff in that box. If you need to put some control electronics right next to that unshielded VFD you might see some issues as near-field radiation can be much worse than far-field radiation (far field drops off at the square of distance in open space, near field drops off much quicker usually.) Sticking a piece of grounded sheet metal or some sort of screen between power electronics and instrumentation can even make a big difference.

You obvious have never done any real installations, you won't see any issues with electronics if it is all installed wired correctly

[reg.miller]

Nobody needs a Faraday cage, just good wiring practice, and your VFD Drive will not emit any EMI / EMF to bother anything around it, when using a input line filter and shield cables and correct Ground Bonding of shields and Ground wires

Why did you ask, if you where going to do what ever craziness you have in your mind any way, I told you how it is done for a normal installation's, if done right (1 ) Cabinet will be better than ( 2 ) separate Cabinets, I guess you are a conspiracy expert as well

The reason I'm asking is because I already have a problematic amount of RFI just running the stepper motors on about 12" of wire from unboxed controller electronics. I doubt that simply bolting this to grounded plate will be sufficient.

There are mechanical reasons why I'd rather not have the VFD and controller at the same point. It is not "craziness". A standard industrial application will have different requirements, constraints and regulations to what I need. I note your comment that one cabinet can be better than two. Thanks.

You are presumably basing your advice on industrial quality VFDs , not cheapo chinese ones which I expect are not made to the same EMI standards.


conspiracy expert? Well it was you who was recommending a flat earth plate !

[ericks]

The reason I'm asking is because I already have a problematic amount of RFI just running the stepper motors on about 12" of wire from unboxed controller electronics. I doubt that simply bolting this to grounded plate will be sufficient.

There are mechanical reasons why I'd rather not have the VFD and controller at the same point. It is not "craziness". A standard industrial application will have different requirements, constraints and regulations to what I need. I note your comment that one cabinet can be better than two. Thanks.

You are presumably basing your advice on industrial quality VFDs , not cheapo chinese ones which I expect are not made to the same EMI standards.


conspiracy expert? Well it was you who was recommending a flat earth plate !

There is always the risk of noise issues.....when you install everything together inside the panel like i also did then separation is very important. Screening the control cables is also a good idea. All drives generate lots of noise. Some of the "better" drives do have built in emi filters....how effective these are i am not sure. We have hundreds of drives in our factory....no filtering installed, and our stuff are all sharing the same panel....however we do have some separation and screened cables

[reg.miller]

are you saying you have hundreds of drives spread around but all the VFDs are in the same panel or that each machine has a panel housing both the controller and VFD?

[ericks]

are you saying you have hundreds of drives spread around but all the VFDs are in the same panel?

No we have many separate panels. but drives are mixed with other equipment.....

[Al_The_Man]

Al, I seem to recall you posting that most of your work was on converting manual machines to CNC. What sort of controllers does that involve? Are they themselves in a metallic enclosure or bare boards?

I have retro-fitted using Fanuc or (preferably) Mitsubishi, I have also designed smaller custom versions built around a PC based Galil Motion and Acroloop cards.
BTW, I have mainly used standard 4 pole motors with VFD's and started when screened VFD motor cable was in its infancy, I therefore mainly used metallic flex conduit with TEW conductors twisted together.
Al.

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[reg.miller]

Thanks for the detail All. What form does the twisting take using TEW? Is that appicable to 3 phase induction motors?

[skrubol]

You obvious have never done any real installations, you won't see any issues with electronics if it is all installed wired correctly

We're not talking about a 'real' installation here. We're talking about a HooFlungDung Chinese finest VFD.

[Al_The_Man]

Thanks for the detail All. What form does the twisting take using TEW? Is that appicable to 3 phase induction motors?

It was 3ph induction motors, VFD ran, It is a bit laborious as you need to take off of three drums and twist them manually over the required length.
The fourth, GND is ran alongside the 3 motor conductors, not twisted with the rest.
Incidentally you will find that since the inception of CNC, the original industrial CNC systems used a similar method as there was no specialized cable back then for the spindle drives.
Al.,

[reg.miller]

Thanks Al. I had decided to use individual multi-strand wires niside a braided sleave, so it sounds pretty similar. I had wondered about twisting but was not sure if this would present unwanted inductance to the VFD output . ( The manufacturer specifically says not to put any filters between VFD and motors. ). I have a pretty short run so it will be simple to do.

If I follow your description, it's just like grabbing one end of the three phase wires and rotating, so it makes a three-start helix.

How many turns per foot are required?

[Al_The_Man]

Thanks Al. I had decided to use individual multi-strand wires niside a braided sleave, so it sounds pretty similar. I had wondered about twisting but was not sure if this would present unwanted inductance to the VFD output . ( The manufacturer specifically says not to put any filters between VFD and motors. ). I have a pretty short run so it will be simple to do.

If I follow your description, it's just like grabbing one end of the three phase wires and rotating, so it makes a three-start helix.
How many turns per foot are required?

One other thing I have traditionally used between VFD and motor is a 3ph inductor/choke this makes it easier on the motor and the VFD, these are typically standard 1740rpm 4pole motors.
Turns/ft are not super critical, the more you can manage the better.
Al.

[mactec54]

We're not talking about a 'real' installation here. We're talking about a HooFlungDung Chinese finest VFD.

Any installation is real Hobby or industrial, they all have to follow EMI code regulations, even more so in a Hobby installation, being residential

There is nothing wrong with the Huanyang VFD Drive it is as good as any other basic drive, in a residential setting it is a must

[mactec54]

There is always the risk of noise issues.....when you install everything together inside the panel like i also did then separation is very important. Screening the control cables is also a good idea. All drives generate lots of noise. Some of the "better" drives do have built in emi filters....how effective these are i am not sure. We have hundreds of drives in our factory....no filtering installed, and our stuff are all sharing the same panel....however we do have some separation and screened cables

In an industrial setting you should know you don't need a line Filter, but if you where following and being code compliant your would be using them

[mactec54]

One other thing I have traditionally used between VFD and motor is a 3ph inductor/choke this makes it easier on the motor and the VFD, these are typically standard 1740rpm 4pole motors.
Turns/ft are not super critical, the more you can manage the better.
Al.

An inductor/choke between the Motor and VFD Drive only helps to protect the Motor, an Inductor or Filter before the VFD help to protect the VFD Drive

An inductor between the Motor and VFD is not normally used for short cable length, but a input power filter or inductor is more important