vfd cable

[ptonsparky]

I'm in need of some shielded cable for Vfd. Load side to motors sharing same conduit. Any suggestion as to a source? 480v 3.2 amp.

 

[petersonra]

belden
alpha

 

[ptonsparky]

Looks like new conduit. Beldens is over a .5 inch. Help ran a 3/4 to feed two motors each on a different vfd. To bad I forgot to mention separate conduits to him. I knew. Shucky Darn.
Another brand is .3 plus. We will see. Thanks

 

[Jraef]

Lapp (Olflex) makes a good product as well.
I use that and Belden.

 

[ptonsparky]

Lapp (Olflex) makes a good product as well.
I use that and Belden.

I watched Lapp's short video which raised another question about fittings and termination of the cable. My intent was to pull it through conduit, to a disconnect then continuing on to the motor. Are there special fittings for this cable? Better to just run the cable exposed?

 

[Cow]

We use Belden VFD cable. They have a short video showing how to terminate the ends but it basically ends up being a couple pieces of heatshrink that seems to be more for aesthetics than necessity. We don't use the heatshrink.


https://www.youtube.com/watch?v=POpB8LlfGnE

 

[ptonsparky]

The runs are just long enough that I will have to buy 500' of cable vs 250' of cable. My help asks me if one motor feed is shielded does the other have to be?. Good question I dont know. Two motor loads in one pvc conduit with another identical run about 4 inches apart for approx 25'.

 

[Jraef]

Lapp (Olflex) makes a good product as well.
I use that and Belden.

For the most part, the stuff they all say about the terminations is based on the fact that elsewhere in the world, they DON'T use metal conduit, they use armored cable, what we often call "Teck Cable". Because the shield is not automatically bonded to the enclosure and conduit, you need those fittings to maintain integrity. So if you are using conduit, and you properly ground the shields (at BOTH ends by the way on power cables), then you would not need any special fittings. But when you run the cables into the VFD cabinet, don't strip everything back as soon as it enters the enclosure, run the shielded cable up as far as you can to the load terminals, then ground the shield drains inside of the VFD at the designated points.

The runs are just long enough that I will have to buy 500' of cable vs 250' of cable. My help asks me if one motor feed is shielded does the other have to be?. Good question I don't know. Two motor loads in one pvc conduit with another identical run about 4 inches apart for approx 25'.

The shielding creates essentially a "Faraday cage" around the conductors. Without it, the output conductors of a VFD can become a somewhat powerful local radio transmitting antenna, bleeding RFI and EMI all over into other things around it, often for quite a distance. In addition, it can pick UP induction from other surrounding sources, such as fixed frequency cable runs right next to it in tray, raceway, etc. Normally we don't worry about that because when everything comes from the same sources and is at the same frequencies, induction effects are cancelled out. But with VFD outputs, they are NOT at the same frequencies as anything else, they are like new sources and varying frequencies, no cancellation effects. I have seen unshielded VFD cables puck up enough induced voltages on just 20ft or so of being run in the same tray as the input cables, to damage the windings on a good quality VFD rated motor. So yes, you absolutely want BOTH of the VFD cables to be shielded.

 

[ptonsparky]

Thank you .