Setting up an Invertek OptiDrive VFD with BLDC motor on a lathe

I decided to buy a decent inverter (Invertek is part of Sumitomo) to (hopefully) reliably drive my lathe motor.
Link to the inverter that i bought.....
www.ebay.co.uk...
The motor in my lathe is a 1KW 95V 3 phase brushless DC motor (BLDC). The key parameters required to set the inverter up are the voltage, current, rated speed and Back EMF at rated speed. I have never found a datasheet for my specific motor, so I had to determine the Back EMF value by measuring it! I'll be doing some machining soon to give it a real test.

[@TheRecreationalMachinist]

Interesting stuff. On the edge of my knowledge really, and although I understood DC brushless and AC induction were cousins, I didn't realise they could be driven in such a similar way. I look forward to seeing more of this 👍 🇬🇧

[@ollysworkshop]

Similar, but also different. I know enough to know that there's a massive rabbit warren (not just a rabbit hole) to fall into on how to drive brushless motors. I prefer to defer to the manufacturers standard settings on this one. Just having a conversation with Haxby shed, and it seems there's more inside Pandora's box. Perhaps I'll do a teardown at some stage to see what lurks within the box of the VFD.

[@TheRecreationalMachinist]

I'm following both yours and @haxby_shed progress with VFD. Even on the slowest pulley setup my pillar drill is a bit fast with its 3000rpm motor. I have the option of swapping it for a 4 pole single phase one, or I like the idea of going 3 phase to give me variable speed and hopefully learn something along the way too.

[@MattysWorkshop]

Gday Olly, looks like you have this all sorted, all them electronics are way over my head, I have no idea on how any of this works at all but I enjoyed watching, cheers

[@ollysworkshop]

It helps that I'm an electronics engineer, but I'm probably skipping over concepts that I take for granted. Glad you enjoyed it.

[@TheKnacklersWorkshop]

Hello Olly, Super video... Very helpful for anyone looking to understand the what the different motors are and what can be hung off the inverter... When you get to making the chuck keys safety switch I guess that will also be plumbed into the inverter. Cheers. Paul,,

[@ollysworkshop]

Hi Paul, I'll hopefully be plumbing in the safety switches in the next few weeks (but don't hold your breath!).

[@GardenTractorBoy]

This was very interesting but this is an area where we have little to no knowledge. Great job setting this up, it appears to work really well. Out experiences of brushless motors is limted to those we have bought on our battery tools and they are great

[@ollysworkshop]

Thanks Joseph. I went for the brushless motor mainly because an induction motor wouldn't fit in the space available. At some point I'm going to build a lathe stand out of box section tube and it will be designed to accommodate a 2.2kw induction motor below the lathe. The 1kw BLDC will then replace the 500w BLDC currently on the milling machine! It's really easy to say this stuff, and somewhat harder to actually get it done!

[@NellsMechanicalManCave]

Very smart mate. Bit above my level of comprehension as I'm only just past understanding how water Mills function 🤣🤣

[@ollysworkshop]

Ahhh, what you need is a VFL (variable fastness lineshaft)! 😁

[@NellsMechanicalManCave]

@@ollysworkshop what a brilliant idea !!!!!!🤣🤣

[@houseofbrokendobbsthings5537]

Hey Olly. Very nice overview and research. My VFD instructions require some dark magic to comprehend. LOL. Your manual looks far superior. May want to fuse the potentiometer. I released the quantum realm smoke particles by accident with mine. Great episode. Sticker is on the way across the pond.

[@ollysworkshop]

Hi Dan. VFDs are complicated things. The last one I did, the 'chinglish' instructions were barely understandable, this one at least the manual was well written. Noted about fusing the pot. Will check if my 10v output is current limited or not. Looking forward to getting the sticker, yours should be with you soon if not already.

[@MrFactotum]

eyup Olly Nice one, 👍👍👍👍👍 but like Neil at NMM a bit above my station and my old school ways, so will be sticking with Tri Leva Myford Cheers See you next time Kev

[@ollysworkshop]

Hi Kev, there's definitely something to be said for keeping it simple!

[@lindsaybrown7357]

I work with VSDs all the time and I'd never power it up without the earth connected. The input RFI filter connects mains voltage to the frame of the VSD. Can give a nasty bite.

[@ollysworkshop]

Hi. The unconnected earth was the motor end, not the supply end. This is a shield earth only and is not a safety earth. Certainly leaving the supply end earth unconnected would be a bad idea, but that was always connected. I have plenty of experience with mains input EMC filters as I spend a lot of time at test facilities EMC testing equipment. Thanks for your comment.

[@lindsaybrown7357]

​@ollysworkshop No worries, wasn't having a dig as you clearly know your stuff. More a word of caution for people less experienced who may be watching. I'd also ensure the motor has a protective earth as the switched DC output of the VSD can capacitively charge the motor frame or shaft.

[@ollysworkshop]

That's ok, if you had the thought, others will have too. The motor frame is earthed via the chassis of the lathe. I wanted to avoid an earth loop as this can cause electrical noise issues, so the motor cable earth is connected at the VFD and both protects and shields the cable to the motor, but is open at the motor end to break the loop. The earthing to everything is effectively starred from the primary earth point at the mains input. On a general note, I should perhaps make it clearer that my videos are "what I've done", and not "how to", but it feels condescending to say that as I'm sure most people understand that a single random KZbin video isn't sufficient information to install something if they don't already know what they are doing. That said, I do appreciate your feedback, and I'll try to make things clearer in future videos.

[@yak-machining]

Does the big 3 phase motor has more torque than the small bldc motor with the same KW

[@ollysworkshop]

Both have approx 4Nm rated torque. For a given rotational speed and power input, the torque has to be similar. The variation would be due to losses.

[@irfansensoy5901]

Hello. I have an air conditioner whose Control Board is broken. Inverter is written on the air conditioner and there is a 3-phase sign on the motor. 4 wires enter the motor N-W-U-V. I think that the back emf measurement is made through the N, that is, the neutral cable. I have been researching VFDs for a long time to bring the air conditioner back to life and I have not seen them used to run 3 phase dc motors anywhere else but you. The DC bus voltage on the control card that controls the motor is 380v. engine power is 1650w. Can I use this engine with vfd?. Also, is a 2.2kw vfd enough for me?

[@ollysworkshop]

Hi. I can offer an opinion, but it's not something I know a lot about. I assume the 1650w motor is the main compressor, with the N in the wiring, it's probably a star winding, so make sure you take this into account when setting up a VFD. I also assume that the control system for regulating the air conditioner is still functional, just the motor Inverter has failed. In this case you should be able to wire in the VFD in place of the broken circuit. The 380V bus voltage is likely power factor corrected rectified mains (√2*240V, boosted to 380V). I would connect a VFD to the main AC supply rather than the bus voltage in the unit as this is done by the VFD internally anyway. Hope this helps.

[@irfansensoy5901]

@@ollysworkshop Thank you for your answer. Below I am sharing a google drive image link of the engine of the air conditioner. drive.google.com/file/d/1vjn-o1WUfnAF3FfDb_PeEeJzZ20-pQ6_/view?usp=sharing The image in the google drive link below shows the engine control card. In addition, there are 4 sockets on the right of 2 orange colored capacitors and the naming of each cable can be seen next to them. drive.google.com/file/d/1Yn_kmeDzm3VIw1WRT6yhaxDKFp-et73X/view?usp=sharing

[@matthewsmetalworkshop]

I don't think your back emf measurement is right. At 50ish volts your motor would be only 50% efficient which would be rubbish. Back EMF is all the voltage drop that is not caused by the resistive drop across the winding. So measure the resistance of the winding and the back EMF is 95-(10*r). Also, you have it wired in star configuration which means you're always powering two windings at once which makes it even more wrong. If it genuinely has 95v windings then in star configuration you should be giving it 190v for maximum power - it may be deceitfully labelled, such that delta would be 42.5v though. Connect it back up the way you're going to use it and measure the resistance across any two phase wires to get your 'r' value.

[@ollysworkshop]

Hi Matthew. Thanks for your feedback. I don't doubt that my back EMF measurement is wrong - I looked for the 'proper' way to determine it and was hit with a wall of maths that i wasn't prepared to wade through! I found a datasheet for the same frame size motor (48V version (lotax.se/images/docs/BLDC/Lotax_BLDC-86BLS-L.pdf), and that shows that the back EMF per 1000rpm is 9.5V. Max rpm is 3000, so i read that as 28.5V at max rpm, so *roughly* half of the rated voltage. I acknowledge that I didn't articulate this in the video, but I was using that number to sanity check the generated voltage that i measured when spinning the motor. When i got the ~50V value I was reasonably happy that i had a 'working' value that I could put into the inverter and not destroy the motor. It is almost certainly not fully optimised. I now notice on closer inspection that it is Vrms/KRPM in the datasheet which puts the 28.5V which means the x1.414 that i did was unnecessary, but that puts my back emf at 36V instead of about 50V. I have actually found some info that i saved at the time and have contacted the supplier of the motor (motioncontrolproducts.co.uk) to see if they have actual values for the motor. I measured the windings as you suggested, and I got 0.15ohms per winding (0.3ohms across 2 windings measured, then /2). If as you suggest it is 95-(10*0.15), that would put the back EMF at 93.5V. From what i have read, if the back EMF approaches the operating voltage, then that's where you loose power, because it cancels the voltage going in, and the current then drops back down. My thought process is that ~50 percent back emf must be the sweet spot, similar to having a correctly terminated transmission line. You know what they say, a little knowledge is a dangerous thing! When I have some more info and done further tests, i will update, either here or by video.

[@MicksWorkshop]

It's all voodoo to me. 😊

[@ollysworkshop]

Does that make me a witch doctor?

[@MicksWorkshop]

@@ollysworkshop At least an apprentice!

[@Mexmanix]

Interesting stuff but you lost me after Ohms law diagram.

[@ollysworkshop]

Sorry about that, I was trying to keep it simple! Hope you enjoyed anyway.