I'd like to install a 3-phase motor (0.37 or 0.25 kW would fit) into my Hobbymat MD65, and control it with a VFD. I've been reading on the topic of VFDs, and looks like the most proper way to install one is to hardwire it to the mains, as well as to the motor.

But in my case, that is not very practical. My little lathe normally sleeps on a shelf, when I want to use it, I take it out and bring it to the workbench. Ideally, I would like a portable VFD unit that would normally stay on another shelf (the lathe takes a whole shelf), and can be brought out and connected to the lathe, when needed. It would be also possible to have the VFD permanently mounted on the wall, but still it would need some way to quickly connect it's output to the lathe when I bring it to the workbench.

I'm contemplating a metal enclosure (perhaps an old PC case?), with an IEC socket for connecting the mains power. Inside would be an EMC filter, the VFD, and possibly a braking resistor (maybe overkill for such a little lathe). Both the lathe and the VFD enclosure should have some sort of 4-pin sockets that could be connected together with a suitable pigtail. Another option would be to pass a cable from the VFD out from the enclosure (through a gland), with a 4-pin plug on it's end, to connect to the lathe.

For forward/stop/reverse/E-stop/speed control on the lathe, I'm thinking about adding RJ-45 connectors on both the VFD enclosure and the lathe, connected via a shielded patch cord.

I have a couple of concerns:

Safety. Most VFD manuals mention that the motor should never be disconnected from the drive during operation (this could destroy the VFD). With 1 or 2 plugs/sockets which could be disconnected, this could be an issue. So the connectors must be lockable, to prevent accidental disconnecting. It might also be a problem if, when setting things up, the VFD is plugged in first and turned on while forgetting to connect the motor. This can be fixed either by proper discipline, or adding an extra pin to the motor connector, which would be a part of safety interlock circuit (until it's connected, the VFD can't be turned on).

EMC/RFI: Reading the VFD manuals and information available on the net (mostly geared towards professional industry), it appears that there are many requirements in wiring up a VFD to avoid excessive interference (I'm in residential environment – my "workshop" is in a cellar inside an apartment building). The connection between the VFD and the motor seems to be an important aspect of that wiring, using a shielded cable, correctly grounding that shield on both VFD and motor sides. I couldn't find any info on properly wiring an arrangement like I'm imagining. I wonder how the plugs/sockets on the motor power wire will affect EMC.

I would like to hear opinions, whether or not this plan makes sense or should be forgotten. If it makes a bit of sense, I hope someone can offer suggestions on implementing this project, for example which connectors would be good to use for the power wire, how to deal with the wire's shield, and any other advice

Thanks!

P.S. Here's a picture from a Russian-language machinists forum, this user installed a "VEM 0,4 kW 1500 RPM, frame size 71" motor and a VFD, and used some kind of screw-on 4-pin socket to connect power to the lathe.

Thanks for the responses guy. I am not thinking about using microphone connectors/cables for this application, even though I've done some searching regarding XLR connectors, and (e.g. using filters on mouser.com) they can be found rated for 250 V 16 A. I prefer to do a proper job, and use appropriate tools, connectors etc, if possible – especially if it can be a safety issue.

I'm in Luxembourg, and most commonly available obvious choice would be a IEC 60309 industrial plugs/sockets (known also as CEE and Commando – a particular brand name). I could probably buy the needed supplies in the local construction supermarket (Bauhaus, Hornbach). However, they are very bulky and their voltage/current ratings are quite an overkill for just powering a little <= 0.37 kW motor on a small lathe.

I have looked at CNC spindles, as was suggested, and found a lot of examples and pictures. If you just search eBay for 2.2 kW spindle, you will find lots of kits containing a 3-phase spindle motor and a VFD unit. Those spindles actually have connectors that look similar or exactly the same, as the one on the picture I posted. It looks somewhat similar, but I rather doubt it being a microphone connector. The connectors themselves are referred to as "aviation connector", searching for that term produces a lot of items from China (in sizes such as GX12, GX16, GX20, GX25, GX30 referring to the shell diameter or maybe outside thread diameter, in mm) – sold at a low price on eBay, AliExpress or Amazon, but I couldn't find actual standards for them, or why are they called aviation connectors. A Chinese company called RenhotecPRO at least has a datasheet, their GX20 connectors are rated at 400 V 10 A (4-pin) or 7 A (5-pin). If one is to believe these ratings, they seem to be fine for the application, and quite compact. With a metal body, can the screen be connected directly to the body (then a 4 pin connector would enough).

I still haven't chosen/bought a VFD unit, but I've already studied a few manuals. Looking at Yaskawa V1000 at the moment. Inverter Driver Supermarket has a quick-start guide for V1000, in that guide there is a 3-wire shielded cable, with 3 wires connected to the inverter's output on one side, and the motor's inputs on the other side, the cable's screen being connected to a ground strip near the VFD unit (also connected to the input power PE wire), and the motor ground (which has a separate "Earth" wire going to it). This corresponds to the wiring diagram in Yaskawa's own manual. So, either I follow these instructions, and use a separate earthing cable (with their own connectors, or maybe even ring terminals + bolts/nuts) – which would be a hassle to setup, or I have the ground wire in the same cable together with the three phase wires, utilizing the same 4-pin (5-pin was also suggested, I suppose for plastic-body connectors) connector?

The printing machinery connector looks small/convenient enough, where can those be found? I've searched for Harting, and they seem to have a lot of different connectors. It's really quite difficult to dig among the professional-level supplier such as mouser.com, there are just so many things available (and many of them quite expensive). I would really appreciate particular connector models (at least families), hopefully those that could be easily sourced and not too expensive.

Ok, I found those Harting connectors as HAN 3A (3-pin +Earth), or HAN 4A (4-pin +Earth). They seem to be very modular: separate housings, plastic inserts (male or female) for particular number of contacts, crimp contacts for which a Harting crimp tool is needed, etc. I've looked at the prices on Farnell, and they are quite expensive! A single connector (as kit) is 30-40 GBP. The crimper is over 150 GBP. Probably one could get by using a regular crimper and/or soldering, but that's not proper, doesn't make sense to pay a lot for nice connectors and then do a half-ass job.

I'm leaning towards trying out these GX20 connectors. Still trying to figure out whether I'd need a 4-pin or 5-pin (5th pin for connecting to the screen, but maybe it could just be terminated to the connector housings?)

I would not be concerned with whether the earth pin would make first and break last, or at the same time as other pins – because I would only be connecting/disconnecting the power cable when the inverter is unplugged from the mains.