Motor terminals

jraef · Jun 6, 2019

Do what you want with contactor controlled motors, but +1 on the VFD controlled motors being terminated directly to the VFD terminals, ESPECIALLY the ground wires and shields (if any). You don't want to run the output conductors in the same raceway / duct as any other conductors anyway; you are just begging for problems if you do.

RTFM for any VFD, they will tell you this.

BOWILLY · Jun 7, 2019

Shielded motor feeds ALWAYS to the vfd/servo...proper grounding beats neatness every time. Other types? Usually dictated by # of motors and what else is in the panel. If at the planning stage, I try to lay it out graphically to isolate voltages, power vs. control, comm cabling etc. The extra time at the planning stage can save you the grief of errant signals when everything is powered.

testsubject · Oct 23, 2019

I know this is a bit of an old post but it seems relevant.

I recently went to SCCR training and the instructor said if you want an SCCR greater than 10k, you have to wire direct to each component. Any time you wire to a terminal, it automatically drops it to 10k. (This includes from VFD to Motor.....)

jraef · Oct 23, 2019

Manglemender said:
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

I have built some really nice panel layouts, then the installing contractor makes it look like a rat's nest when they make up the motor connections in the field.

Not one of mine, but typical of the worst...

jraef · Oct 23, 2019

testsubject said:
I know this is a bit of an old post but it seems relevant.

I recently went to SCCR training and the instructor said if you want an SCCR greater than 10k, you have to wire direct to each component. Any time you wire to a terminal, it automatically drops it to 10k. (This includes from VFD to Motor.....)

Maybe yes, maybe no. There are some terminal blocks available that have been listed with higher SCCR ratings. They are never the cheaper ones. But if you don't specifically check into it and find those, that is essentially correct.

https://literature.rockwellautomation.com/idc/groups/literature/documents/pp/1492-pp019_-en-p.pdf

bill4807 · Oct 23, 2019

jraef said:
Maybe yes, maybe no. There are some terminal blocks available that have been listed with higher SCCR ratings. They are never the cheaper ones. But if you don't specifically check into it and find those, that is essentially correct.

https://literature.rockwellautomation.com/idc/groups/literature/documents/pp/1492-pp019_-en-p.pdf

Perfect because i use 1492-J and 1492-L type.

I wish in the spring series 1492-L3 series they made a 2 circuit block like the 1492-JD3 that would use up to 16awg. All i can find are the 1492-LD and the largest wire you can fit is MAYBE 18awg..

I usually run motors from contactors to terminals anything 12awg and under , and motors on VFDs 80% of the time straight to the drive.

jdbrandt · Oct 25, 2019

JeffKiper said:
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.

To this point, if the choice is to have the field installers run the field wiring to the output terminals of the VFD, there should be provision made (i.e. physical space) for the large and typically unruly bundle of power wires coming in from the field.
And, not a small point, the orientation and line-of-sight to the VFD terminals; which can be troubling, if the VFD is mounted too close to the bottom of the enclosure, and the field installer now needs to be horizontal and in a prone position to simply land the wires...hopefully on the correct terminals.
I, too, have seen both methods. But, the 'run the VFD output wires to a terminal strip' method is just plain nicer, cleaner, and, at the end of the installation, easier to manage.

testsubject · Oct 25, 2019

jdbrandt said:
To this point, if the choice is to have the field installers run the field wiring to the output terminals of the VFD, there should be provision made (i.e. physical space) for the large and typically unruly bundle of power wires coming in from the field.
And, not a small point, the orientation and line-of-sight to the VFD terminals; which can be troubling, if the VFD is mounted too close to the bottom of the enclosure, and the field installer now needs to be horizontal and in a prone position to simply land the wires...hopefully on the correct terminals.
I, too, have seen both methods. But, the 'run the VFD output wires to a terminal strip' method is just plain nicer, cleaner, and, at the end of the installation, easier to manage.

I agree with you on all counts; I just brought it up because according the SCCR instructor, doing this would reduce the SCCR of the panel to 10k.

As Jraef mentioned, there are terminals out there with higher SCCR rating but they are expensive.

paraffin power · Oct 25, 2019

Manglemender speaks the truth

g.mccormick · Oct 25, 2019

testsubject said:
I agree with you on all counts; I just brought it up because according the SCCR instructor, doing this would reduce the SCCR of the panel to 10k.

As Jraef mentioned, there are terminals out there with higher SCCR rating but they are expensive.

Automation Direct has terminal blocks with 100kA SCCR rating
https://www.automationdirect.com/adc/shopping/catalog/terminal_blocks

rupej · Oct 25, 2019

testsubject said:
I agree with you on all counts; I just brought it up because according the SCCR instructor, doing this would reduce the SCCR of the panel to 10k.

As Jraef mentioned, there are terminals out there with higher SCCR rating but they are expensive.

But you can also use fuses that reduce the available fault current to 10k, thus a 10k rating on terminal blocks does not derate the entire panel.

rpoet · Oct 30, 2019

I have to go through terminals on a current project. The TINY Mitsubishi D720 VFD only accepts conductors 16ga or smaller - it's a 1/2Hp drive, so not surprising. It really is "Baby's First VFD." It's soooo small.

The EC for the job wants to run 12ga wire out to the motor. I might be able to convince him to run #14. Marshaling TB's solve this problem.

-rpoet

Phil Buchanan · Oct 30, 2019

rpoet said:
I have to go through terminals on a current project. The TINY Mitsubishi D720 VFD only accepts conductors 16ga or smaller - it's a 1/2Hp drive, so not surprising. It really is "Baby's First VFD." It's soooo small.

The EC for the job wants to run 12ga wire out to the motor. I might be able to convince him to run #14. Marshaling TB's solve this problem.

-rpoet

Even if it's small it can still produce enough noise to cause problems to the rest of the system so I would still use VFD cable direct to the drive.

They make small VFD cable. The link below is to a good Belden VFD cable that is 16 AWG in size.

https://catalog.belden.com/techdata/EN/29500_techdata.pdf?pdf=VFD-Tool

jets · Oct 30, 2019

14 AWG VFD cable

Automation Direct also sells 14 AWG VFD cable, maybe even 16 AWG but never looked for it.

rdrast · Oct 31, 2019

Anything less then 250HP here must go through either terminals, or a power block mounted in line with the terminals. Direct connections to any device are frowned upon. 250-500 HP, we can discuss it, but I still prefer terminals. 500 to 2500 HP, usually the devices themselves have ample room for connections, so they can be wired directly.

Also, when I'm having panels made, I will usually tell the builder if I want terminals at the top or bottom (or sides) of the enclosure. I do have many cases where the drive panel is on the floor below the motors, and just running straight up out of the top of the cabinet with top terminals makes for a nice installation.

Motor terminals

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