Motor terminals

JeffKiper

Lifetime Supporting Member + Moderator
Join Date
Jun 2006
Location
Indiana
Posts
2,447
When designing panels do you land motors on the VFD/contactor or run them to a terminal strips? Terminals will make it easier for the field guys. The terminals will add a few more potential failure points.

I'm on the fence. Ive seen both and done both. Wr are trying,ti make a standard for our designs moving forward.
 
For neatness and ease of installation (plus we tend to move our machines around a bit) I wire everything to terminals for wires 12AWG and smaller. Larger motors are typically wired directly to the drive.
 
From experience, if as long as the VSD is directly at the bottom of the panel, direct is perfectly fine, however if it is above other terminals, i would prefer terminal wired
 
For EMC reasons, You should take motor wires back to the drive and terminate the screen at that point. Many drives are specifically equipped for that.

Nick
 
+ 1 for drforsythe. That's pretty much what they do in our panel shop. And we're ISO certified, so that's a standard with us.
 
I was on a panel that had 50 VFD and they terminated directly on the drive. It made the installation not a clean as it could have been.
 
The best thing you can do if your motors are below 10HP or so is to always use motor cables/receptacles. I've used the Turck ones quite a bit, but I know others make them. The receptacle wires directly to the drive/contactor and makes a neat installation. The field guys love it because the connections are incredibly simple.

In other cases, I always have the contactors at the bottom of the panel (seems to be the general side that wiring comes in/out) and they wire direct. I don't put wire duct below the contactors at all - field wiring is direct from conduit to the contactor/drive. I always try to provide a grounding bar at the bottom of the panel as well.

I have had a few panels where the installations come through the top of the panel instead of the bottom. In those cases, I have used a terminal strip at the top of the panel wired to the other side of the contactor/VFD.
 
I always go to the drive / cont.
I wouldn't trade dependability for looks ever. Especially since I'm the guy who has to come during the night to fix it!
The terminal block is just one more point to keep tightened and maintained.

Also,what voltage is the terminal block rated for.. Not likely the 1000V to match the VFD cable if being installed in a VFD application.

Iv seen the regular AB terminal blocks fail and be the source of a ground fault at least a couple times in my day.

No terminal blocks for motor connections in my panels!
 
Contactor is up to you.

For drives, you should always go to the drive and use the cable shield clamp that should come with the drive. Rectified and IGBTed electricity is very noisy.

I have seen fancy terminal or bulkhead connectors for motor cables that would be fine, but that's a lot of cost to avoid just planning cable routing to make direct to drive look neater.

EDIT: Harting HanQ connectors are on a machine right in front of me for VFD cable bulkheads.
 
Last edited:
This an old document but what it says about circulating/stray currents is still valid. http://www.compliance-club.com/archive/old_archive/020112.htm

The biggest drive system I've built in recent years was 66 drives and it worked fine. I also remember one machine with only a few drives that was problematic because the motor screen wiring was terminated at the gland plate rather than the drive. Noise radiated through the entire panel causing comms networks to fail.

Nick
 
I always have the field guys land directly on the drive/contactor. I don't see the need to make it "easier" for them. Terminating inside a nice new panel should be by far the easiest part of the installation. (y)
 
Personally, I tell people installing our stuff to go right to the drives. That tends to reduce the possibility of EMI/noise inside the enclosure. Some drives are better than others but many of the drives out there today have some pretty good VFD cable clamps that make clamping onto the shield pretty easy.

Keith
 
Being the guy that gets called when it doesn't work, I prefer motors wired directly to the drive/contactor. Fewer failure points, and easy to trace.

Bubba.
 

Similar Topics

Hello all, In my facility we have multiple 3HP 460V motors that are being controlled by VFDs which drive conveyor belts. The drives are randomly...
Replies
2
Views
173
Hi everyone, This is my first time posting, so please forgive any omissions or mistakes. I am attempting to control the velocity of a stepper...
Replies
18
Views
744
Kindly, has anyone tried to control Lenze servomotors with Siemens S120 drives ? Any special hints ? Have some concerns for the resolver and servo...
Replies
5
Views
180
Dear Members, Hello, we are working on a project and facing an issue with the plantpax 5 PMTR library, we have a bidirectional motor, which has 2...
Replies
6
Views
185
Hi all, New here and new all round to PLC`s. We have a servo drive that runs a cross travel beam backwards and forwards. I am having trouble with...
Replies
3
Views
134
Back
Top Bottom