Shielded VFD cable from 16 AWG through 4/0

What symmetric drive cable actually contains

VFD cable is built around three phase conductors held at equal spacing for the whole length. That symmetry is the point of the construction. When the conductors sit in a fixed triangle at a defined lay, each phase presents the same impedance, and the common-mode current a drive produces at its switching edges has a predictable path back to the source.

The shield is either a foil tape at full coverage bonded to a drain wire, a foil and braided copper combination, or on heavier constructions a corrugated copper tape that also serves as armor. Insulation is XLPE or EPR, and the jacket is PVC or a thermoplastic elastomer, sometimes with a nylon skin for abrasion in tray.

Grounding is split rather than central: three bare equipment grounding conductors, one in each interstice between the phases. Keeping the ground close to each phase lowers the impedance the drive sees at high frequency. Cable with a single center ground is a different product and is reviewed as one.

Why the motor lead comes out of a retrofit

A plant replaces an across-the-line starter with a drive, or swaps an aging drive for a newer unit with a faster front end. The existing motor lead is usually THHN or XHHW pulled in conduit with one ground. It carries the current, but it does not control the reflected wave at the motor terminals, and it lets high-frequency current return through conduit and building steel.

So the motor lead gets replaced with shielded cable, often terminated with full coverage at both ends, and lead length is shortened or re-routed while the electricians are there. Cable pulled a year earlier comes back off the rack, still tagged, still on its reel, in footage long enough to be worth a second installation.

Retrofits strand new cable too. A contractor buys a reel for one drive, uses part of the run, and the balance rides back on the truck. Both directions produce reviewable lots, and they arrive with very different paperwork.

What separates a reviewable reel from scrap

The shield is the first thing to look at. Foil dragged over a sheave tears back from the cut, and a cable that cannot be terminated with full coverage has lost the property that made it VFD cable in the first place. Corrugated armor forgives more, but a flattened section usually means a basket grip was set in the wrong place.

Storage decides more than age does. A reel that stayed indoors on a rack in a storehouse holds up for years. The same reel parked on a dock apron through a lake-effect winter will take water at the open end and wick it under the shield.

• Reel tag with original footage and readable jacket print
• Shield intact at the cut end, foil not torn back
• No standing water inside the reel wrap
• Cut end taped rather than crushed in a pull grip
• Footage long enough for a single motor run

Where these lots come from in Ohio

Drive work follows the Northeast Ohio industrial base: steel finishing along the Cuyahoga, forging and heat-treat shops, coatings plants, and the process industries further south. A mill that changes the drives on one line will generate a dozen motor leads at once, in sizes from 16 AWG control tails up to 4/0 on the big motors.

Electrical contractors on institutional and water treatment work accumulate the same cable one reel at a time. Both kinds of lot get the same treatment: read the construction off the jacket print, confirm shield type and ground count, measure the remaining footage instead of trusting the tag, then look hard at both ends.