DIY Belt Grinder Build Questions

Are you talking about the 220VAC single phase from the house to the VFD unit needing shielding? Or, the 3 phase cord from the VFD to the motor?

I've never heard of shielding being required.
 
The cable from the VFD to the motor is subject to a lot of high-frequency noise. As I understand it, the shielding will help prevent radiation of that noise. I’ve seen issues with the noise before, where wrapping each motor lead around a ferrite core helped tremendously.
 
For 20A, 12AWG is fine. I think for a short run, 14AWG should be alright, but I like to oversize a little, just in case. I'm pretty sure SOOW is what I used. It looks like SJOOW insulation is rated for 300V, while SOOW is 600V. I don't think I'd be comfortable being right on the edge of the insulation rating for SJOOW.

I don't use any shielded cable for my VFDs. In theory, there is electrical noise being emitted from the wires due to the way they generate the 3 phase. In practice, it hasn't bothered anything in my garage. Even the import DROs don't seem to mind it, and they seem to be the things most people see issues with. There's also that this is a grinder. It's not something that you are going to likely be running with sensitive electronics also in use. My biggest reason for non-shielded is that it was easy to get locally. The local HD had a remnant that was inexpensive as well, so I figured I wasn't out much if I ended up replacing it.
 
I will say that the machine I worked on with noise issues had a very long cable from the VFD to the motor. Like 15’. We didn’t have much experience.
 
Okay, I bought 12/3 SOOW and 12/4 SOOW cord from Home Depot. The VFD has 2 size cutouts. I bought PG21 cable glands to seal the cables on the VFD and motor. The larger cutoff fits perfectly with a PG21 cable gland.

But, the other one is causing an issue. The problem is the smaller cutouts are too small for the SOOW cable on both the motor and VFD.

Here's the dimensions:
VFD and motor cutout diameters: 0.875" = 22.2 mm
12/3 SOOW cable diameter = 0.59" = 15.0 mm
12/4 SOOW cable diameter = 0.64" = 16.3 mm

PG21 Cable Gland
Cable diameter range: 0.51" - 0.71" (fits)
Threaded diameter: 1.11" (too big)

PG16 Cable Gland
Cable diameter range: 0.39" - 0.51" (too small)
Threaded diameter: 0.89" (too big)

1/2" Trade Size
Cable diameter range: 0.39" - 0.55" (too small)
Threaded diameter: 0.84" (works)

So, what does everyone use?

The 1/2" trade size is close to working, but still too small. The fact that the motor and VFD openings are so small makes me question whether 12 AWG cord is needed and whether SOOW (600 V) cable is needed.

The motor datasheet does state 12 AWG, but makes no mention of the voltage rating. Other places on the Internet do show that 14 AWG is more than adequate for a 3 phase, 2 HP motor running at 220 V.

I plan on addressing any noise issues after the fact. Cough42 did a episode on this on his lathe VFD conversion, so I can use that as a guide. I plan on keeping my cables short between the VFD and motor.
 
My VFD isn't sealed, so it just has flexible entry ports for the wiring. Could the ports for cable glands be metric?

Voltage on the motor side is 220V. I personally like insulation to be rated for close to 2x voltage as "stuff" happens in real life that can damage insulation. It may be that I'm paranoid and it's a non issue.

Wire size needed depends on current. Which depends on the motor. What's the motor plate say? It might list it as "FLA". I suspect it's likely low enough that you can use 14AWG. I think my 2HP motor is 11A, which would be fine for 14AWG.
 
Looks like the motor current at 230V is less than 5 Amps (less than 6 Amps at SF 1.15). Strange since the motor manual recommends 12 gauge wire. Seems like massive overkill. I can see the need for 600V cable more than this gauge wire.

I already have 12/4 SOOW cord, so I'll guess I'll have to figure out a way to use it. It's not cheap even though I only bought a small amount. I ordered PG16 cable glands which will fit the holes in the VFD and motor. Maximum opening is 0.511". Cable is 0.64".

Maybe I can open up the cable gland at the cost losing the water proof feature? I don't need water proof, but I'd like it impervious to grinding dust. That's the whole point of using these.



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I guess they could be concerned about startup surge currents. Not really an issue with a VFD as they generally soft-start. Even then I'm not sure you could get enough current to be a problem. But you have it and they recommend it, might as well try to use it.

If you open one up and there's no rubber left, you could use some silicone sealant to seal it up.

Not ideal, but would the 3 wires make it in without the outer jacket? You can connect the ground outside the motor itself. Maybe replace it with some heatshrink? With some careful setup, you should be able to even seal up the opening in the outer jacket from water incursion, not that it really matters in this case. It would protect the wiring from abrasion though.
 
Well, I got it working. I removed the rubber seal from the PG16 cable gland which gave me a little more space. Then, I carefully sliced off some of the heavy outer insulation from the 12/4 SOOW cord. With some pushing and coercion, I was able to get the cord through. I'm not sure if it's a waterproof seal, but it's should be grinding dust tight.

The opening in the boxes were a little tight for the OD of the cable gland, but I was able to push them in since they were plastic.

I fired up the motor and it ran great. The KBAC-19 (1P) 10001 VFD worked great and has no programming steps to go through. Every option is set by little shunts on the PC board. Very easy.

All right. On to the mechanics! With my design nearly done, I need to start order some steel!
 
I'm just about done with my belt grinder project. What does everyone recommend for finishing? Caswell Black Oxide kit?
 
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