VFD AC Inverter and Induction Motor

[Michael Hunt]

VFD Cable in Class 1

VFD Cable in Class 1

We are installing automation in a C1D1 area, and the integrator calls (from Italy) calls for Shielded Cable. Of course the cabinet is in the unclassified area 70+ feet away. Flexible Cord is permitted because the application is a mixer (501.140(A)(1)), but we intend to run cables for two motors together in IMT except where flexibility is needed.

Since 400.8(6) prohibit using flexible cord in raceways. How can I maintain the shield, and provide seals at the firewall.

Yes VFD cable, I have only used it once.

But in the little I have read they do want shielding, a metal raceway usually takes care of this.

The one time I used VFD cable was in a very large control cabinet, it was my understanding at the time the engineer was concerned with the VFDs un shielded output would create problems with the other electronic devices in the same cabinet.

Soon I will actually be shielding some VFD conductors for testing purposes.

 

[Jraef]

What they mean in that section of the code is what is referred to unofficially as "portable cord", the rubber insulated SO or SJO type stuff meant to be laid on the ground, essentially in free air. You can't run it in conduit because it has no current rating enclosed in conduit; that was never the intended use so the mfrs don't bother. The code just keeps you from making that error.

There are plenty of shielded cables that are rated for running in conduit or trays etc., including flex conduit. Look for "VFD cable" or "inverter cable" from people like Belden, Lapp or other specialty cable manufacturers. Most distributors who sell VFDs will have it available.

If by "flex" you meant "extra flexible" where the mixer is constantly moving and you would have used that SO cord, then your only choice would be to have a separate local terminal box where the flex cable is needed.