Type of Wire Recommended for Output of VFD

[jtgrace87]

I am installing (3) VFDs and it will require #8 AWG wire on the output side of each drive. What is the recommended type of wire for the output side of VFDs? I have heard that it is not a good idea to install THHN on the output side. Is this accurate? The application is (3) 25HP Blower Motors.

 

[petersonra]

I am installing (3) VFDs and it will require #8 AWG wire on the output side of each drive. What is the recommended type of wire for the output side of VFDs? I have heard that it is not a good idea to install THHN on the output side. Is this accurate? The application is (3) 25HP Blower Motors.

If you are going to use single conductors THHN is probably as good as anything.

Some people have been advocating the use of special VFD cables that the cable manufacturers are now pushing. I think they are one of those things that make sense in some cases, but I also think that most times you won't see any real difference in performance between running single conductors and the expensive cables, especially if the single conductors are run in EMT or ferrous metal conduit.

If it makes you feel better, twist the single conductors together with a drill before pulling them. IMO, you will get most of the benefits of the expensive cables without the expense.

OTOH, most of the VFD cables are also rated as tray cable so they can be just put on a cable tray, which might be convenient.

 

[iceworm]

Just a suggestion:
My first choice to to see what the mfg specifies. What does the manual say?

ice

 

[Aleman]

We use cable made for VFD outputs. It should be shielded and the shield landed at both ends. THHN or other rated wire is fine in conduit.
The important thing is to try to minimize noise from getting into your control circuits. It is also helpful to use line reactors on VFD outputs
which reduce noise and spikes which can damage insulation.

This is what we typically use on VFDs:

http://www.omnicable.com/spec-sheet...ncy-drive-variable-frequency-drive-cable.html

 

[GoldDigger]

I love the color code "chart" in the specs. For 1, 2, 3, or 4 conductor configuration the color is black. Period.

 

[Aleman]

I love the color code "chart" in the specs. For 1, 2, 3, or 4 conductor configuration the color is black. Period.

Wires are numbered. Omni does make other cables some of which are colored, but the VFD cables are black except ground which is green.

 

[iceworm]

.... It is also helpful to use line reactors on VFD outputs which reduce noise and spikes which can damage insulation. ...

How do you select the line reactors?

.... This is what we typically use on VFDs:

http://www.omnicable.com/spec-sheet...ncy-drive-variable-frequency-drive-cable.html

How do you pick this cable? Owner specs? drive MFG specs?

ice

 

[MasterTheNEC]

Type MC Cable works well for this type of application also. We find that many use the PVC Jacketed Type MC for this application and are pleased.

 

[Cow]

I love the color code "chart" in the specs. For 1, 2, 3, or 4 conductor configuration the color is black. Period.

Like mentioned above, the Belden VFD cable we use has numbered leads.

 

[Aleman]

How do you select the line reactors?


How do you pick this cable? Owner specs? drive MFG specs?

ice

For reactors we go with what is specified by the drive manufacturer. The cable is sized by the load same as any other motor. There are plenty of VFD cable
manufacturers. We go with Omni because we can get it fast and prices are reasonable.