Practical VFD use for VFD newbies

[mickeyf]

I understand the theory and basic electronics, but have never used or installed a VFD.

Most of the info I can find about VFDs is from motor manufacturers and seems oriented towards industrial applications like conveyor belts, not hobbyist machine tools. So far, the advertisers on AliExpress have not been willing to post a link to a user’s manual, which is something I’d really like to see before buying.

What I have gathered from here and other forums so far is

1) Especially with the low cost models, get one a couple of times the rated capacity,
2) A good enclosure is a worthwhile investment – keep out the dust and grit to prolong it’s life, and contain the fire when the thing fails, to prolong yours,
3) Make sure it supports a braking resistor so the rest of the circuit does not try to absorb that energy and go up in smoke.

What I’m wondering about is:
What are the maximum and minimum frequencies (speeds) that people typically use and that are practical?
If using a machine that was/is controlled by belt changes, how is torque effected? Do you run the VFD at a higher speed and belt down, or what? Does this matter?
Apparently all recently manufactured motors are “inverter rated”, but many home machinists are likely using older, used motors. Has anyone had any issues with this, or does this actually matter in any practical way?

Anything else I should be aware of?

Thanks in advance!

 

[David]

http://www.etech.net.au/Huanyang/HY%20Series%20Inverter%2020100627.pdf

That's as close to the manual for an HY VFD as I can find. I have a nice print version in the shop but I can't find the equivalent online.

Definitely size up the VFD. 1 HP motor, buy a VFD rated for 1.5hp min.
An enclosure helps keep the dust out but two of mine have just hung on the wall with no ill effects.
A braking resistor is a good idea but not all import vfds support them.

On my mill I belted for low speed ergo torque and cranked the frequency up when I needed faster spindle speed. I plan to do the same on my lathe. I ran my mill down to 30 Hz and as high as 90 Hz with no ill effects. It was an inverter rated motor though.
This has the benefit of helping mitigate the loss of torque at lower frequencies.

 

[slow-poke]

I had one of those cheapie VFDs fail, others seem to be happy with them.

I have had great success with used name brand VFDs with external brake connections and vector control that provides low speed torque. Mostly eBay scores for <$100 zero failures so far.

How low you can go depends on:
1) How sophisticated the VFD is, Yaskawa will give full rated torque at near zero RPM
2) Motor cooling which is often just a fan blade on the motor shaft so if turns slowly the fan isn't doing much for cooling. That being said I dial mine down very low (barely turning 60 RPM ) sometimes and often drill (large bits) at low speeds perhaps 200RPM and my motor never gets beyond warm.

 

[YotaBota]

This the VFD I bought for my grinder, I just wired it up and it runs the 1.5hp motor okay.

VEVOR VFD 3HP, 2.2KW, 10A, 1 Phase 220V-240V Input to 3 Phase 220V-240V Output Variable Frequency Drive, 0-400Hz VFD for AC Motor Speed Control | VEVOR CA

VEVOR VFD 2.2KW 10A 3HP offers unmatched quality with 220-240V input/output, energy efficiency, easy setup, robust safety features, and silent operation.

www.vevor.ca

There is a manual on the site that shows all the setting.

My lathe I use all the gears for initial speed settings and fine tune with the VFD. Nice to be able to speed up or slow down while continuously cutting.

 

[Elektrishun]

The advice I would offer is depending on how much your investing in a VFD you might want to make sure it is well supported with basic replacement parts.

Likely the first thing to go will be the cooling fan. Should be an easily attainable and affordable part.

While working as a maintenance electrician I once replaced a failed cooling fan that was $300 (ouch!). Custom design for that manufacturer, no alternative could be found. I doubt you will run into that with the models you will be considering.

 

[phaxtris]

i have the cheapest Chinese 2.2kw vfd (the white one) on my lathe, it has lasted a good couple years running its (12.5" swing, 2hp), and ive ran it pretty hard on occasion. I dont have an external braking resistor, but i do have some braking enabled and it hasn't let out the magic smoke yet.

i have the little more expensive Chinese 2.2kw (the dark grey one) on my cnc router running a 2.2 kw motor, that's a pretty easy life, but it hasn't died yet either

i dont use mine much for speed control on the lathe, although it is nice to be able to turn the spindle speed up or down to adjust for weird harmonics, i think the vfd's are nice for the other features, the ramp on speed, braking speed, easy control wiring. The router runs the spindle at whatever i command it, 0-24000rpm, it doesn't much care

 

[BaitMaster]

The best of the cheap china VfD’s are the dark grey Huangyang ones.

The cheapest CSA rated one you can get that works good is the Automation Direct Durapuls VFD.

Used off of eBay for a name brand drive is legit. Especially if you go for something upper echelon like Yaskawa.

Upsize the China ones. Don’t worry about upsizing the others.

Usually motor speed is limited by bearings, not the drive. Most conventional motor bearings are rated to about 4000rpm. Running faster then that you risk burning up seals on bearings.

A really nice drive with a really nice motor can do full torque at 0 rpm.

A normal drive/motor (on a machine tool) will do generally well between 20 and 72 hz. Running a fan/pump is completely different as those are variable torque loads.

Outside of those parameters, you will need a purposely selected motor/drive combo to be confident.

Ask away, we love spinning in circles about VFD’s almost as much as lathe leveling.

 

[Susquatch]

@mickeyf - Here is the manual for the Teco A510.

I agree with most of what others have posted. But here are a few comments not mentioned.

I don't think the resistor is intended to protect the VFD. It just facilitates faster stops than otherwise possible by providing a place to dump the energy. Most VFD's will work without one.

I have 4 VFD's in my shop and 2 VFD rated motors. For non VFD Rated motors, my max and min set points are 45 and 75. These speeds are fast enough at the bottom end to keep the motor cooling going and slow enough at the top end to avoid frying the bearings.

For the zero rated motor on my Bridgeport Clone, I set the limits at 6 and 120. This motor combo could be set to 1 rpm if I wanted, but I can see no practical reason to do so.

For the 10:1 motor on my Lathe, I have set the limits at 15 and 90. It could be 6 and 120, but I prefer to play it safe. This extends my lathes minimum speed from 70 rpm down to just under 20 which meets my needs wonderfully!

I chose these speeds to stay within the ratings and to avoid compromising the life expectancy of my systems.

Another nice thing about using a VFD is that it doesn't need to be set and forgotten. If you change your mind because your motor is getting too hot when you run it slowly, you can simply change the lowest speed to be higher.