VFD Panel wiring question

alexbeatle

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Feb 2010
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Hello, all!

Doing panel VFD (PF525) wiring.

Question about the wires on the VFD T1-T2-T3 output bus. The plan is to connect the T1-T2-T3 outputs to the terminals to which then the field wiring will be attached.

The field wiring will be VFD rated cables.

Do the short wires from the T1-T2-T3 outputs to the terminals need to be VFD rated cables or can be THHN wires which can handle the load (in my case THHN 600V AWG10 for the 1HP 480VAC load).

Thank you.
 
Hello, all!

Doing panel VFD (PF525) wiring.

Question about the wires on the VFD T1-T2-T3 output bus. The plan is to connect the T1-T2-T3 outputs to the terminals to which then the field wiring will be attached.

The field wiring will be VFD rated cables.

Do the short wires from the T1-T2-T3 outputs to the terminals need to be VFD rated cables or can be THHN wires which can handle the load (in my case THHN 600V AWG10 for the 1HP 480VAC load).

Thank you.
How are you routing those wires to the terminals? In general, the best practice is to mount the drives such that the field motor leads go directly to the drive terminals. Adding more terminals adds risk of problems without much payback.

In addition, you will read in the PF525 manual that they want you to have the motor ground leads AND the shield drain wires for them connected DIRECTLY to the ground terminal on the VFD, not to a ground connection elsewhere, even if they are all tied together. So now you will be either violating that, or making your field installer run SOME of the motor wires to your terminal blocks, but having to make the shield drain wire and the ground lead longer to go up to the VFDs. Nobody is going to like that.
 
I agree that if at all possible, you should wire direct to the VFD.

You could greatly lower your SCCR rating with the terminals, and as Jraef mentioned, the manual specifies how the cable should be connected directly to the VFD PE terminal.
 
How are you routing those wires to the terminals? In general, the best practice is to mount the drives such that the field motor leads go directly to the drive terminals. Adding more terminals adds risk of problems without much payback.

In addition, you will read in the PF525 manual that they want you to have the motor ground leads AND the shield drain wires for them connected DIRECTLY to the ground terminal on the VFD, not to a ground connection elsewhere, even if they are all tied together. So now you will be either violating that, or making your field installer run SOME of the motor wires to your terminal blocks, but having to make the shield drain wire and the ground lead longer to go up to the VFDs. Nobody is going to like that.

Good point.

I have seen examples of the new systems which have it done the way I described, which makes me question their decision making.
 
How are you routing those wires to the terminals? In general, the best practice is to mount the drives such that the field motor leads go directly to the drive terminals. Adding more terminals adds risk of problems without much payback.

In addition, you will read in the PF525 manual that they want you to have the motor ground leads AND the shield drain wires for them connected DIRECTLY to the ground terminal on the VFD, not to a ground connection elsewhere, even if they are all tied together. So now you will be either violating that, or making your field installer run SOME of the motor wires to your terminal blocks, but having to make the shield drain wire and the ground lead longer to go up to the VFDs. Nobody is going to like that.

I agree that if at all possible, you should wire direct to the VFD.

You could greatly lower your SCCR rating with the terminals, and as Jraef mentioned, the manual specifies how the cable should be connected directly to the VFD PE terminal.

Per,
https://www.anixter.com/content/dam/Suppliers/Belden/Brochures/VFD Termination Guide 2017.pdf

It's not best practice, but if no sensitive components use it's ok
 
You should be using 1000V rated cables on VFD. The THHN in your panel is not rated for that.
Asking for problems in my opinion. I VFD cable to the reactor, no terminal blocks, every time. No exceptions. Between the VFD and the reactor, same thing, only use the VFD cable.

Feeding the VFD, I use 600 volt rated, 105 degreeC TFFN machine wire.
 
I have to differ all wires in or out of a panel terminate at terminal block the only exception would be if the wire is large and a terminal block is impractical
look at the pictures and ask witch one would you want to work on a service call in the middle of the night.
as for shielded cables the shield should be connected at one location only as close to where it enters the panel as practical the do make shield ground bars for that. I have gone in on startups where the electrician wired to the wrong VFD or fails to correctly torque the T leads on the VFD then I had to replace the VFD
so many other problems to go into them here.
Keep it simple stupid some installers don't know how to work in panels you are just asking for trouble letting in there.
allow then to connect to a terminal block only minimize the damage they can do.
the one pane shown is a pome example that case the installer was the same guy that wired the panel he didn't know what he was doing but did it anyway
I was contracted to do the field startup only the hole project was a disaster from the start I finally had to walk but that's another story.
 
Normally, I am my own installer. I get help from contractors to run pipes and wires. Sometimes they get to make field connections but that depends on who it is. Your right though, Iv had "installers" normally electrical contractors make some pretty inexcusable messes of my VFD terminations. Some of them folks are crude, used to wiring houses and pulling wire. I'm an electrician by trade so I know the attitude. They get er done quick so they can get out not ever thinking about the folks who's jobs don't end at 4:30 but only when the plant runs. The most surprising thing though to me, is that even though there is a detail drawing on how to terminate the VFD cable, then we talk about it, then I say "Hey remember to look at the drawing", and still terminate completely wrong with the drawings laying untouched...... mind boggling.


Worst as a contractor I had run a parallel feed for a 400 panel connection.
They energized the breaker and quickly realized they had a phasing mix up on a couple conductors. Yup... Boom, then, after they "fixed" it, they short circuit tested the breaker one more time..... Then I showed them how to meter out the conductors and megger their installation.

I still don't like putting motors on terminal blocks though.

((((GaryS, I/We can't see your pics.))))))
 
I am going to try this again soy about the pic's before
I had the file size to large
also you should use MTW not THHN wire inside a panel
as I said before I don't want anybody doing field wiring to anything the terminal block that is why we put them in there

Panel 1-1.jpg Panel 1-2.jpg Panel 1-3.jpg Panel 1_4.jpg Panel 2-1.JPG
 
I am going to try this again soy about the pic's before
I had the file size to large
also you should use MTW not THHN wire inside a panel
as I said before I don't want anybody doing field wiring to anything the terminal block that is why we put them in there

I have a spool in front of me that says on it, MTW, TEW /TFFN and 105*C.

I have one spool here that even says Boat Cable on it but has the same MTW rating marked on it and 105*C.

Its from Domtec..... oddd.

I suspect that my supplier of wire may be shopping around and getting different brands with different markings..... Im gonna harass them a bit! I hadn't noticed the different markings on some of this wire. The one thing it all has in common, is the MTW and the 105* rating.
 
the wire marked boat is tined copper it's required on all marine applications
THHN in nylon coated and only maintains the full voltage rating if the nylon coating is not broken it's a little smaller outside diameter so you can stuff more in a conduit.
MTW has more smaller conductors makes it more flexible for us in panels
most us them interchangeable. all the wire's in a panel should be the same type
I have even seen welder cable used in panels for larger wire sizes it makes the easier to work with
but everything leaving the panel should connect to a terminal block
 
Most of our panel have the VFDs to terminal blocks if space allows with single wires per terminal. Customers & UL shops have never questioned it with zero problems in the 20+ years it's been done here. Basically everything we have is 1HP and under, so that may be a factor as well.

Makes field installation much easier and our build guys love it, especially on the drives that have special bolts (I think Nidec has T15s) or "hidden" terminations for grounds that aren't easy to get to once the panel is in an enclosure.
 
We build many cabinets per year with VFD's. All VFD motor cables go directly to the VFD's, no exceptions, like jraef's recommendation. In order to do this in an orderly fashion we have the VFD's low in the panel, right above the terminal strips, never higher. There are never any other components between the VFD's and terminal strips. We also typically have several load cell cables entering the panel, typically signals very sensitive to EMI noise. Good quality shielded VFD motor cables, shield thoroughly connected to earth at both ends. That is the only way that works for us.
 
Thank you, all.

As I understand from all of the above and from other doc's, the best practice is to wire the VFD cables directly to the VFD itself.

If doing a retrofit (adding more motors) and the panel already has wiring:
VFD -->*TTHN*-->TB block-->*VFD cable*-->Motor.

Suggest wiring the addions the same or differently (directly)?
VFD-->*VFD cable*-->Motor.

The power components (VFDs, contactors, etc.) and logic components (PLC, controllers) are in separate cabinets (PLC-to-VFD via Ethernet) with separate grounds, so shouldn't be noise issue. Unless cross-talk between VFDs!?
 

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