Advice on Selecting VFD Cable

Tim Ganz

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Join Date
Dec 2010
Location
Dallas, Texas
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689
I am looking to use Lapp VFD cable and have configured it for the size I need in the attached file. But Which one of these 4 is the best choice for protection of the cable and motor and noise mitigation?
 
Two of those have a pair of control wires. The two that don't have the control pair have different jackets, TPE and PVC. All four are shielded and designed for noise mitigation.

Here's a little info on the difference between TPE and PVC.
 
Looks like the differences are the features of the cable itself.

Do you need an additional 2 conductor "signal" pair as they label it? I would hope "yes" so you can disable the VFD if the local disconnect is thrown.

The other looks to be the details of "2XL" or non "2XL" cable which look to be related to installation environment. I'd read the details of each part number to decide.

EDIT: Always the bridesmaid.
 
Last edited:
Shielded motor leads are a great improvement in the VFD world but, as usual, the marketing people tend to run AMOK with some of the claims. With regard to radiated noise, expect a big improvement. With regard to protect of the motor insulation due to ringing voltages and reflected wave, expect no change. If you have long motor leads, you will need a line reactor, dvdt filter, or sine filter pretty much the same as if you have run THHN in a metal conduit. With regard to common mode noise or ground noise, the problem is made a lot worse with the shielded cable due to the increase in capacitance to ground. If you have short leads or if you have a solidly grounded wye 480/277V power supply, or if you have a drive isolation transformer, this difference may not be significant. On the other hand, if you have a floating delta power source or high impedance grounding, or maybe even a lack of a grounding network in your facility, then the motor lead cable can actually aggravate an already bad problem.
 
We have also used a lot of the SLIM cable. Especially when someone needs their machine to be CE rated, like Dick DV said, the radiated noise goes way down.

The signal pair is sometimes used for when the motor has a brake. I suppose it could be used for wiring up a temperature sensor in the motor as well.
 

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