How to do a VFD Conversion and Motor Swap for a Lathe

My import Lathe (Sieg SC-10) recently broke down due to the driver board / variable frequency drive inside shorting out. In this video I'm showing how I installed a new motor and matching VFD and talk a little about VFD settings and other technical details.

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🔧 LINK LIST for tools I use in my videos:

[PhilVandelay]

Thanks to Flexispot for sponsoring this video!
You can use the Promo Code "YTB30" to get a $30 discount on all orders over $500!

[emirouribe]

By far the best channel on YouTube!
No stupid music, no talking heads or talking hands, no stupid ramblings.
Just clear and concise explanations of every skillful step that keeps you glued. Brilliant.
Absolute joy to watch. Very well done. Subscribed!
Thank you!!!

[jimsvideos]

If your drive does it, a jog (i.e. momentary on) switch is great for threading.

[larrybud]

Out of all the machining/metal working videos I've watched, I've never seen an air powered hand chamfer tool. Very cool, looks great for non critical parts, and no setup! Also you do a great mix of 3d printing where appropriate.

[billdoodson]

You will be happy to know that the Wago connectors seem to be taking over the world. I use them quite a bit for house wiring in the UK. If you use the correct junction box they become a connection that is permenent and never needs inspection.

[mkegadgets]

Great video as always. I really dig the bracket for the controller. I like how it slides in and out so you can work on it. Make adjustments on it and it’s permanent but not permanent. Look forward to your next video.

[Alexander]

In case you want to get even more power out of the motor you could use a VFD that puts out 400V (yes they are available with 230V 1~ input).
With that you can effectively increase the motor power by the square root of three, so about 2.6kW for your motor at the same increased speed aswell.
These small motors can usually be spun up really fast, VEM rates their frame size 80 motors for 13000 rpm max.

I believe someone else already mentioned it that the motor in your configuration must be connected in delta, not star as shown in the video.
Otherwise there will be quite a performance loss. With a braking resistor in place you should be able to break in less then a second.

[DaveMcIver]

Excellent video as always. You're never hesitant to tackle the more complex tasks Phil, and always completed to the highest standard we've come to expect from your channel.

[DaveEtchells]

(Another excellent vid!)
For people considering a VFD, especially thinking of adding one to a brand new lathe, here’s some advice from my own experience.

I ordered my brand new lathe with a 3-phase motor on it so I’d be able to use a VFD to get both higher and lower speeds out of it, as well as the convenience of just turning a dial for moderate speed changes without messing with gears.

I’d assumed that I could just put the VFD between the lathe and the AC line, like a phase converter, just with variable frequency, but this isn’t at all how they work. Try it like that, put the power button and the VFD will either do nothing or trip offline instantly.

A VFD needs to be connected directly to the motor and control _everything_ the motor does: Starting up, running, slowing down, stopping quickly and reversing.

This meant that I had to completely rewire the lathe, so the controls, end stops, etc would all connect to the VFD and simply ask nicely for it to tell the motor to do things :-)

Figuring out the VFD and rewiring the lathe was a significant PITA. I’m glad I have it set up that way now, but if I had it to do over again, I’d skip the VFD, use the gearbox and just be satisfied with its normal speed range.

If you’re buying a new lathe and can’t afford one that has a built-in VFD, unless you have some use case that absolutely needs the higher/lower/variable speeds, just get one with the single phase motor and be happy 😁

If you *are* installing a VFD though, I highly recommend Invertek. They’re more expensive than cheap no-name Chinese alternatives, but their tech support is absolutely top-notch. They know the products inside and out and it was literally the best tech support experience I’ve had with any company selling technical products.

[criggie]

HAH you're one of the few creators who can make the sponsor's advert roll interesting. Now repurpose the desk as a bike lift :)

[Ziraya]

For the speed sensor EMF sensitivity, you might have luck using Cat7 cabling. Unlike Cat5, e, 6, a, cat7 is Shielded, meaning the foil wrap protecting the wires is grounded. It's weird to hear because cat6a also has foil, but as far as I understand that mainly helps to protect the pairs from each other, while 7 it also protects from the world. In twisted pair, both ends are bridged across a transformers and rather than voltage being sent down one or both, the transformer is excited by another winding and that causes power to shift from one wire to the other, creating a negative voltage on one and a matching positive voltage on the other, Each creates it's polarity of an electric field and because the wires are held close, they couple to one another as they shoot down the wire, this keeps them strong. The twist then ensures that any noise they experience is "Common Mode" noise, the same magnetude and polarity on both wires. When it gets to the far end the symmetric signal passes through the transformer and excites an output on another winding, while the common mode hits the transformer and current doesn't flow across it, so it doesn't excite the other winding.

The ungrounded foil wraps keep the electric field coupling inside. It's balanced out between the two wires, so it also balances out in the foil, and doesn't extend beyond. But because the foil isn't grounded, common mode noise passes through it. At very high frequencies like we're using with 2.5gig 10gig, 20gig, etc, cross-talk is a big problem, and it's reasonable to put environmental considerations on the engineer laying out the building

In both cat6a and cat7 the pairs are individually wrapped, so you could put power down one pair, power to the sensor up another, and then signal plus the corresponding opposed supply voltage down a third pair. You don't need to terminate it, as long as you ground the 5 shielding wraps on both ends. If this doesn't cure it of EMF, then you probably want to build a sheet metal box around the sensor and behind the display, ideally both boxes containing the unsheathed portion of the wires.


The same coupling effect can happen in all wires, that's why you want the signal to be paired with it's opposing voltage, so that the opposite polarity of the signal will couple down that wire, strengthening the signal; and why you want both/all legs of a power-carrying cable to be near each other. AC-live couples to AC-neutral, and importantly uncoupled power emits a lot more EMF. Usually you can't avoid running high power wires together, but if you have them separating much anywhere, you might fix some EMF problems by putting those wires together, or even binding them together with cable lacing or zip ties. Low voltage DC shouldn't matter unless it's carrying high frequency data.

[physics-to-technology]

Hello, had the same defect on the board of my SC10 a year ago.
Two short -circuited IGBT of one motor phase.
The original IGBT are no longer available, have not been made for a long time, but there are good newer replacement types.
The real reason for the destruction of the IGBT were the smd drivers of the IGBT.
The defect on this channel has controlled both IGBT at the same time, which of course leads to their dead.
The drivers are in good quality (much better than the no-name in it) by Infineon for a few cents.
As a precaution, I renewed all three drivers with the Infineon.

The control has been more than 500 hours of operation since the repair

Of course, it is too late for you to experience this, now with the VfD and the new engine. ;-)

[unibeastbeats]

that 3D printed bracket is a nice solution

[MRCan]

Phil, I marvel at the diversity of your knowledge in your videos. Fantastic work again!

[HangarQueen]

Great mod, Phil. I've been planning to replace the wimpy motor on my mini-lathe for a while ('coz its low RPM torque is nonexistent), and your video gives me some good information on VFD tuning and braking. One more project added to the long and growing list.

[jeffvader]

Yet another fantastic video, thank you. Your enthusiastic attention to detail is staggering.😊

[Bennyboy-dog]

Very nice mod. More off the shelf parts and greater flexibility sounds like a win to me.

[paularbon]

Thanks Phil for a great video. It is a very worthwhile upgrade to your lathe. Excellent machining and commentary.

[OverbuiltByHenry]

Very nice conversion! I personally would have picked the same motor power but a 1500rpm one, that way you get twice the torque than the one you have there. Torque is more important than speed on these type of machinery. If you need more speed (like finishing passes) you can crank the Hz up on the vfd, you can run these type of motors up to 100hz safely (obviously making sure you don't draw more current than the one is specified on the motor plate).

[ollied]

I guess it's a bit late now since you already changed the panel to get rid of the momentary contact start/stop buttons, but in my experience you can usually configure the inputs of the VFD to change state on the rising or falling edge of the signal which is what you need for a momentary contact. Also Vishay multi turn wirewound potentiometers are very nice for controlling the speed in this kind of application. Great job as always and I really like the channel!