Beginner VFD questions, I want to do it right.

[Cheapo]

I'm looking at the GS20 because I want something with support, it also has FOC which potentially makes the motor run better and cooler on less power than a plain sensorless speed controller.

Reading the manual it lists motor wire requirements and it says minimum cable size 8AWG, maximum cable size 8AWG. My cable will be at most 4'.

It sounds like a 10AWG substitution should be almost overkill even though it doesn't meet the spec.

I see the attraction of cheapo VFDs but for this machine which is so nice that I got so cheap, I can spend $300 on VFD stuff and feel great about it. I kind of doubt that the cheapo VFDs have as many features as a GS20 and I do want to try an auto-reversing tapping mode so the extra expense doesn't bother me.

I still have the question about running the VFD in a sealed ammo can, is that enough air volume or will I need to open the lid on jobs that take more than a few minutes?

 

[Cheapo]

As Randal mentioned above, there is absolutely no need to use that large of wire. Size the wire to match the amp draw. I would be surprised if you could get a #10 AWG wire to fit into the terminals of that VFD. I use ferrules on my wires to make things easier.

The manual is very specific about ring terminal sizes for the motor wire connection at the VFD. I was planning to stick with that.

The electrical box on the motor side is another issue, it looks like a rat's nest of wires that were hastily cut out when the machine was removed. I have used wire nuts for connections like this in the past, now I'm wondering if I should switch it up to something like Wago connectors? They seem to be the new fad in residential wiring but I have never used them.

 

[mksj]

You need to provide a specific model/input voltage. In general I would use 12AWG for the input power for a 2Hp or smaller VFD 230VAC input, or 1 Hp at 120V input. Motor cable would be 14AWG for VFD's 3Hp and under, 1 Hp and under you could use 16AWG. My recollection is that the input side needs to be rated at a minimum of the 125% of the input rating of the VFD regardless of the motor size, output wiring is minimum 125%of the motor FLA.

Wiring from the VFD to the motor should be a direct connection, so usually locking spades on the VFD end and ring terminals on the motor end if to a terminal block, wire nut is OK if to wires and then wrap in electrical tape.

 

[rabler]

There is no reason you need wires bigger than are in your wall running to the 120V outlet you are going to plug it into. The VFD is stepping voltage from 120 up to 220V, so the amperage on the output goes down compared to the input (unlike say, a 12V car battery charger).

I see on page 2-24 of the GS20 manual where it says the minimum wire gauge supported by the terminal is 8 gauge for the GS21-11P0. Frankly, that is a error in the manual (That is a mechanical spec, not an electrical spec). They are putting the 120V input VFD for 1HP in an oversized C vs A frame (likely to accommodate the additional capacitors needed), and some technical writer copy/pasted the specs based on frame size. I suggest calling Automation Direct technical support to confirm. Also, page 2-3 lists a minimum airflow of 16 cfm, which a closed ammo can will not meet.

 

[7milesup]

Reading the manual it lists motor wire requirements and it says minimum cable size 8AWG, maximum cable size 8AWG. My cable will be at most 4'.

It sounds like a 10AWG substitution should be almost overkill even though it doesn't meet the spec.

As Randal pointed out, the spec in the manual is wrong. Also, maybe I misread your comment, but 8AWG is larger than 10AWG. It seems that you are saying 10AWG is bigger than 8AWG, which is incorrect.

I purchased a 12x16x8 enclosure for my WEG VFD and I am currently installing a cooling fan in the enclosure. Your ammo can will not provide enough cooling.

One last thing regarding support questions for your VFD. I, too, purchased mine from Automation Direct WEG CFW300 VFD. I had a quick question regarding powering a light when the VFD was switched to "run" mode. The tech support guy said it couldn't be done, and yet one of their videos shows it being done. I figured it out on my own...

 

[macardoso]

Admittedly did not read all responses before answering so I apologize if these have been answered already.

The AutomationDirect GS20 series of drives are really nice. I would recommend them.

My responses are based on my experience as an industrial automation engineer focused in motion control and power (VFDs and medium voltage)

Is it a bad idea to buy a 1hp VFD for a 1/2hp motor? If I have 220v, how about a 3hp VFD? If it is a bad idea, why?

Typical rule of thumb is that you can double the size of the VFD to the motor but it is not recommended to go further. Why? The VFD has Current transformers (CTs) measuring the output waveform and current draw on each phase. These are processed by and analog to digital (AD) converter and used in the motor control algorithm. When the drive is significantly oversized to the motor, the resolution of the current measurement becomes poor. If the drive can resolve 1028 current values, but the motor is 1/4 the rating of the drive, then for that motor, there are only 256 usable current values (just an example, not actual numbers).

When the drive is oversized significantly, poor motor control can result. Symptoms include: increased motor heating, increased torque cogging/nonlinearity, surging in speed, etc.

These are less commonly seen in simple V/Hz control modes, but will become more obvious with "better" motor control algorithms like Sensorless Vector Control (SVC)

Can I add a 5 conductor twist-lock connector to move one VFD between multiple 3 phase motors?

Sure! Just don't disconnect while the drive is powered - especially when the motor is running. The inductive breakdown will generate a high voltage pulse back to the drive which can damage the IGBTs on the drive (output transistors).

Shielded wires? All of my cable runs should be short.

Absolutely. Read the GS20 manual's section on noise mitigation and follow it carefully. VFDs are one of the worst sources of electrical noise in an industrial environment and troubleshooting is a complete headache.

Should I try to do a star ground to avoid loops?

Yes. Read the manual section on grounding.

I heard the GS20 has memory for a few motors, has anyone successfully done VFD swapping between tools like that?

Yes, this is common. You can add a selector switch to the digital inputs to switch between motors. AD tech support is decent and can probably help you set this up.

I want a mechanical E-stop button front and center. The NEMA versions have an optional safety interlock switch, is there a good way to do that without spending an extra $3-400 on a NEMA version (that doesn't work on 110v)?

The GS20 drives have a Safe-Torque-Off (STO) input on the drive. This allows you to directly connect a dual channel ESTOP button and achieve a safety rated torque removal. Highly recommend doing this. You do not need the NEMA version. Read the manual section on Safe Torque Off.

What filters and other stuff should I add to protect the VFD and reduce injecting noise in to the power lines and RF noise through the air?

Line filters help protect the drive from poor utility power quality. This is not usually an issue in residential power and can usually be omitted without issue. Most filters do not protect the line against conducted RF emissions from the drive anyways.

If you are concerned about radiated RF emissions, focus first on proper grounding and bonding. The drive should be placed inside a metal enclosure with star grounded subpanel, door, and enclosure body. Nano-crystalline ferrites can be added to the VFD output wires for reducing higher harmonics of the drive carrier frequency, but these are typically not needed for basic drive installations.

Is the DIN rail mounting kit substantial enough to mount the VFD on the head of the drill press (with cables hanging) or will it be falling off the rail all the time?

Put the drive in an enclosure and properly mount that with screws!

It's going to be run in a shop with some dust and potentially a little smoke from cutting fluid.

Again, I would highly recommend putting the drive in a proper enclosure. The drives aren't cheap and a single metal chip getting inside (the covers are slotted) could ruin the drive.

I was looking at two drill presses at auction, the one I got and a more typical floor mount press with a drill that has an auto-reversing tapping feature. Can I add some micro-switches to the quill, a stopping resistor and a few buttons or relays to make an auto-reversing tapping feature?

Absolutely. The VFD should be able to stop a drill press very quickly, although a braking resistor will be needed. All that would be needed is a SPDT button. This would be wired to a digital input on the drive. When not pressed, the input identifies the running direction as FWD. When pressed the running direction is REV.

You'll need to program the drive to use the braking resistor and to use a fast acceleration/deceleration time.

 

[macardoso]

With the mounting drawings, it looks like the setbacks should allow me to mount the VFD in a USA style .50 cal/5.56mm ammo can and have enough air space on each side. Will the 1hp VFD running a 1/2hp motor be able to live in a closed ammo can or do I need vents?

100% you'll need vents. A basic filter fan intake on the bottom and a exhaust grille on the side near the top would be recommended. Get one that can run right off the 120V line.

I've done a ton of heat calcs on VFD enclosures and can pretty much guarantee you'll need it even without running the numbers.

 

[macardoso]

Automation Direct seems to sell a ferrite choke for the motor wires and a capacitive filter for the mains, both in the $20 range, are these worth getting? If not, what do you suggest? I don't think there is a GFCI on the power circuit.

Fair warning, the ferrite toroid from AutomationDirect is physically huge (even the small one). They only offer 2 sizes to cover their entire portfolio of drives. The smaller one is appropriate for something like a 10HP drive. No harm in using it, but you're going to be surprised by how big it is.

Ensure the ferrite does not touch the metal enclosure. There will be substantial eddy currents inside the material (that's the point!) and bringing it in close proximity with the enclosure, or worse a direct short, will generate a lot of heat.

I think there is a cable clamp kit for connecting and grounding the cables at the VFD, is that a good idea or is a ground stud on the ammo can sufficient for grounding?

You want the shortest path for noise back to the source. I'd recommend using their shielded cable clamp. If the noise goes to the enclosure ground stud first, the enclosure can actually radiate the noise making your situation worse!

Remember, bonding (for noise reduction) is different from grounding (electrical shock protection). The goal is to maximize surface area and contact area. Wire mesh sleeves and 360 degree clamps are much better at giving noise a low impedance path to the source than say a run of wire and a ring lug.

This is due to the skin effect where high frequency AC waveforms (noise) travel only along the surface of a wire and experience increased impedance in applications where surface area is not maximized

I'm looking at the GS20 because I want something with support, it also has FOC which potentially makes the motor run better and cooler on less power than a plain sensorless speed controller.

FOC is great but somewhat of a pain to set up. Again, this is a place to not more than double the size of the drive to the motor. An autotune is necessary for the drive to measure the motor response. Honestly for a basic spindle application, V/Hz or SVC will be more than sufficient.

The electrical box on the motor side is another issue, it looks like a rat's nest of wires that were hastily cut out when the machine was removed. I have used wire nuts for connections like this in the past, now I'm wondering if I should switch it up to something like Wago connectors? They seem to be the new fad in residential wiring but I have never used them.

Wire nuts, ring lugs and a bolt, or Wago "ice cubes" are all acceptable options. Be aware the Wago blocks have an amperage rating on them since the current must travel through the block rather than just having the wires mashed together. Use a couple wraps of electrical tape to keep everything tidy and insluated.

 

[We-R-138]

I agree with this. I bought a G20 for my old Powermatic wood lathe, it works great. I bought a $50 eBay VFD, it drives a 1/3HP motor just like expected. They both have all the features needed. Why pay more?

BTW, I had zero issues with interference, fault tripping, buzzing, etc.

I am undoubtedly on board with your statement about no faults, interference, etc..

Although, programming with the indecipherable manual and applying the wrong parameters. sure can burn one up in a hurry! In particular the YL600 ( i believe thats the one on my mill) .

I did have a hard time deciphering the manual's critical info and language barrier, but found a comprehensive manual here on the site.

Just don't mount it on the wall without a lick of protection and then use a 4" flycutter with a somewhat high rpm and a decent depth of cut in ally. That evening, i offered a spontaneous and free fireworks display for my neighbors! Hey, it "was" my first attempt at 3phase vfd and a total crap mill. With near 1/2 turn backlash on the dials. and "newly replaced lead screws". claimed by the PO. He used a 1"-5tpi 60* "all Thread. :{. LMFAO!

Now that lead screw is in the landfill...

 

[mksj]

As much as it would be nice to have a top notch VFD system with everything done per the manual, there is a practical and financial balance that needs to be factored in as well as benefit to risk. I have yet to see a factory installed VFD system on small lathes and mills use shielded cables, use RFI/EMI filters, use DC chokes, etc. A 4' motor cable, it is a point of diminishing return spending $100's for a shielded cable with grounding strain reliefs, proper pre-post VFD noise filters, etc. There is also the added complexity of knowing how to do these things correctly and have the proper tools, etc. A must do in an industrial environment, but a costly proposition for most hobbyist who are scrimping and get the cheapest VFD they can find. It is reasonable to use shielded cable for the low voltage control and speed pot, but more important as to the routing of the cables and proper grounding/enclosure. I do use shielded cables with star grounding on my builds, but as I mentioned I have yet to see it implemented on dozens of manual lathes/mills with the factory VFD installs. Getting into CNC, that is a totally different level and requires a higher level of electrical noise mitigation.