# VFD Power



## erics37 (May 7, 2009)

Not sure the configuration of teck90 but most drives I believe require radially symmetrical, shielded cable. Generally you want to invest in drive cable at least for the drive output.


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## John Valdes (May 17, 2007)

Special cable is not always required. When I sold and supported drives, special cable was rarely used and I think it was not even available.

Individual conductors, over sized EGC and in separate metal conduit was SOP.
We also used shielded cables for signaling.


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## Concept (Mar 30, 2012)

Installed countless drives and it has been rare to use specific drive cables.


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## sparkywannabee (Jan 29, 2013)

If you don't have a lot of room and you are dealing with big conductor sizes you can always use some welding cable or DLO(diesel locomotive) as well.


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## JRaef (Mar 23, 2009)

You don't HAVE TO do anything, but you SHOULD be concious of what you do and the ramifications of ignoring the special conditions of VFD circuits.

You CAN use shielded VFD cable, it protects the motor from standing wave generation and helps with bearing damage issues (although not completely). 

Or

You CAN use regular wire, twisted together with the ground conductor, in *steel* conduit, grounded at both ends. If you do, I would ALSO include a dV/dt filter, especially if you have more than about 50' from drive to motor and 480V, or a motor terminator that absorbs and standing wave spikes.

Or 

You CAN use tech90 cable IF the armour is *steel*, AND you have a dV/dt filter on the output of the drive.

Everyone should read this thoroughly, even if you are not using Rockwell drives, it is probably the best VFD installation "bible" I have ever seen. It comes from the old Reliance people when Rockwell bought then, so it is based on roughly 50 years of VFD experience.
http://literature.rockwellautomation.com/idc/groups/literature/documents/in/drives-in001_-en-p.pdf


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## micromind (Aug 11, 2007)

I realize there's all kinds of special stuff you're supposed to do with VFDs, the actual reality is that I have personally installed well over 100 VFDs in my career, and every one of them uses basic standard wiring on both line and load. 

The most 'abusive' one I can think of is a 5HP gear pump about 580' from the VFD. The VFD is in a MCC, and there are both line and load reactors present. From the MCC, there is a 1" EMT that runs about 100' inside of a building, then 1" rigid for about 200 more feet. The remainder is 3/4" rigid. 

In the 1", there are 3 #12s for the VFD motor, plus 2 #16s for its on-off switch (120AC). There are also 3 more #12s and 3 #10s for 2 other motors that run full voltage, plus their controls. One of the full voltage motors drops off when the pipe goes to 3/4". The other one goes even further than the VFD motor. 

This was installed about 2 years ago, the VFD runs from about 40 - 80% 24/7. The other 2 motors run anywhere from an hour on - an hour off to a few hours on - an hour off. 

No trouble so far.......

P.S. All 3 motors are 460 volt, and controls are 120.


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## John Valdes (May 17, 2007)

I am certain the new cables are an improvement. Since its been a few years since I was involved in these matters, I do not know what new standards are being used.
I used regular wire because the new cables were not available back then.
And I am fairly certain if they did exist, cost was the factor that made them an afterthought.


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## triden (Jun 13, 2012)

JRaef said:


> You don't HAVE TO do anything, but you SHOULD be concious of what you do and the ramifications of ignoring the special conditions of VFD circuits.
> 
> You CAN use shielded VFD cable, it protects the motor from standing wave generation and helps with bearing damage issues (although not completely).
> 
> ...



Thanks for the info. I forgot the that armour had to be iron, but it is in fact aluminum. http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet329

The power run is only about 20 feet, but will be within a bunch of control cables. They are small powerflex4 drives running some produce conveyors. The controls it will be along are basically on/off digital logic and not communications cables, so I think it should be fine. Thanks for the PDF though...I'm reading through it slowly.


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## jsilva76 (Aug 9, 2013)

JRaef said:


> You don't HAVE TO do anything, but you SHOULD be concious of what you do and the ramifications of ignoring the special conditions of VFD circuits.
> 
> You CAN use shielded VFD cable, it protects the motor from standing wave generation and helps with bearing damage issues (although not completely).
> 
> ...


Thanks for the doc very nice.


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## jsilva76 (Aug 9, 2013)

Thanks for the doc very nice.


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