VFD questions

I recently bought an old Bridgeport, and got a Teco VFD to power it off of the 240 1ph in my shop. Wiring it up looks straighforward, but I do have a couple questions. First- when I wire up remote peripherals such as Forward/Off/Reverse, and a potentiometer, what kind of cable do I want? It says something about shielded twisted pairs. Can I buy a cable with multiple twisted pairs, or should I run separate cables for the different functions? I did find 26Ga cable with several twisted pairs, and each pair looked to be shielded. Thoughts?

Secondly- How much range is practical on a VFD? I like the idea of leaving the V-belt in one place, and doing everything else with the VFD, but what extremes are practical? If it's on the pulley for say, 1200 RPM, can it go down to 100 RPM? Will it have much torque? What about 'overclocking' it? Can you safely run the motor at significantly higher RPM's than it was originally intended? I'm just trying to find out the limits without letting the magic smoke out of the VFD, or my mill.

Third- The instructions specify 10A fuses between the VFD and the motor. Are these necessary? I bought some, and a fuse block; I'm just wondering how risky it is to skip the fuses.

First: Shielded twisted pair is fine, If you keep i away from the power wires, it should be good even as plain twisted pair, but go with shielded, it may oay off in fewer "WTF moments".

Second... practical is no more than maybe 3:1. Torwue will be OK if the motor can cool itself at that speed (many cannot) but you lose POWER. Belts and gears maintain power, and adjust torque to keep the power, the VFD maintains torque, and the power changes to keep the available torque.

third... You do whatever the manufacturer specifies. If they say fuses, they must know why they say fuses, so put them in. It may be a condition of the UL recognition. Without the fuses, the thing may not have the UL safety recognition.

Thanks! I guess my first question was really whether or not the various peripheral cables will interfere with each other. In other words, will the cable controlling for/rev interfere with the one from the speed control pot? I plan to use the for/rev switch on the mill to control the VFD, and hang a pot on the mill so that speed control is handy. I might even add a digital display, depending upon where I mount the VFD, and what I do to protect it from the machine shop environment.

The control wires normally do not interfere with each other.

The motor side wire interfere with anything close, and power side wire may interfere with things.

Protection.... shielded wire, oil resistant outer jacket. Run it where it is not subjected to abuse.

More questions- I want to put the VFD in an enclosure to keep dust and chips out. I'm going to mount it on the wall, but I also have a surface grinder in the same room, and periodically take old rusted stuff apart with an angle grinder, so there will be dust. Moisture and oil won't be a factor. How big an enclosure for a non-vented set-up? I read somewhere that it should be at least four times the volume of the VFD, which would put me at 10X10X6 or bigger. Do I want NEMA 1, or should I go up to a really sealed NEMA 4? For control, I'm going to use a shielded CAT5e cable, and install jacks on each end for a clean, simple set-up.

MushCreek said:

For control, I'm going to use a shielded CAT5e cable, and install jacks on each end for a clean, simple set-up.

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Don't do that. Cat 5e is not designed for resilience on mechanical tools that can and do vibrate. It's designed to cheaply get information across long distances with a minimum of packet loss and little if any movement over years of service. Though it may be twisted pair it's comprised of 8 leads, each 1 singular, easy to break wire. You would be far better off with some quality multi-strand shielded wire, I really like Lapp Olflex for applications like you're wanting to do, and there's plenty of it way cheaper than an OEM distributor will charge you for a relatively short length of it on eBay.

MushCreek said:

More questions- I want to put the VFD in an enclosure to keep dust and chips out. I'm going to mount it on the wall, but I also have a surface grinder in the same room, and periodically take old rusted stuff apart with an angle grinder, so there will be dust. Moisture and oil won't be a factor. How big an enclosure for a non-vented set-up? I read somewhere that it should be at least four times the volume of the VFD, which would put me at 10X10X6 or bigger. Do I want NEMA 1, or should I go up to a really sealed NEMA 4? For control, I'm going to use a shielded CAT5e cable, and install jacks on each end for a clean, simple set-up.

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Size of enclosure for that is specified right in the VFD maker's manual. It will seem overly large. Believe what the maker sez. They actually tested it.

The manual for my TECO L510 does show an enclosure size, but it is fan cooled. I can do that, of course, but wasn't wanting to mess with a fan and making a filtered intake.

As for the cable- Where do I find a few feet of quality cable? On Ebay, they want to sell you 1000'.

Below it what I used in the very same VFD, worked great.

McMaster-Carr

Part# 6452T44

No-Conduit-Required Control Cable, Seven 18-Gauge Wires

Thanks! That's not a shielded cable though. I looked through their catalog, and found some shielded cables. Looks like a 10' minimum, and some of those cables run $3-4 a foot. I guess it's worth the extra money to have a permanent solution. Still, for that money, I could get a dozen finished CAT5e cables, and simply plug in a new one if the old one started to act up. Either one would probably work on a home mill that will likely sit for months at a time. Decisions, decisions.

MushCreek said:

Thanks! That's not a shielded cable though. I looked through their catalog, and found some shielded cables. Looks like a 10' minimum, and some of those cables run $3-4 a foot. I guess it's worth the extra money to have a permanent solution. Still, for that money, I could get a dozen finished CAT5e cables, and simply plug in a new one if the old one started to act up. Either one would probably work on a home mill that will likely sit for months at a time. Decisions, decisions.

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CAT <wotever> "patch" cord is flexible. Stranded, not solid, and fine strands at that. Meant to stand handling, flex, and vibration.

You do NOT want to have to terminate it, though! RPITA compared to solid. Use it as-had, "factory" RJ45 plugs, both ends.

I tend to put a punch-down RJ-45 socket at each end, drop the on-machine / on-device wires to it with a Krone or Siemon tip on my punch-tool, use stock patch cord lengths between, replace if/as/when needed - RJ's too as they corrode.

Not quite as cheap as dirt, nor as readily found. But close enough.

VFD or DC drive control inputs are protected, buffered, and conditioned for industrial environments already. Far less picky than 10-Gig-E over copper.