220V single phase to 380V three phase

[mekanik]

Hi Guys
The single phase motor on my Emcomat 7 has a burnt coil, i tried a local rewind service but they have a huge backlog so can't rewind it.
They also wanted £700(estimated) plus vat.
Spares are almost non existant for my lathe model, but i was fortunate enough to find a three phase motor in the Netherlands. the bearings were wrecked but i have replaced them. the windings show no sign of overhaeting so just fingers crossed that it is going to work.
So could anyone point me in the direction of a suitable converter that will convert single phase to three phase and boost the voltage to the required 380V.
Would it run off 220V three phase.
Regards
Mike

Motor info
Type 80A/2/4SM
380V /1.3 /1.3 A
0.45 /0.3 Kw
2800/1400 rpm
50Hz

[JohnHaine]

From the plate this seems to be a 2 speed motor, that is, wound as a 4 pole but the windings switchable to run as 2 pole at double the speed (i.e. 1400 & 2800 rpm). If the star point is accessible you could change it from star (380v) to delta (230v) running, though I think that's a bit trickier with a 2-speed motor. You could also run it from a lower voltage 230v inverter anyway, it will run at whatever speed is selected but just give a bit less power. Apparently if you actually reduce the speed to about 30Hz you can get the same power. Inverter Drive Supermarket sell drives, possibly 230v in 380v out ones, and they also have a note on their website about running at lower speed. Find them with Google.

[mekanik]

Hi John
Thanks for your prompt reply. Yes it is 2 speed done with a mechanical switch. manual shows single phase and three phase link up. is that delta config.
Have attached a copy of the 3 phase wiring that i got when i first bought the lathe, the recently purchased motor is Emco specific but don't know if it's same as shown in the circuit diagram.
will check out your link, What size (Kw) would be required?
will try and get a photo of the wire colours on the 3 Phase motor if that helps.
Kindest Regards
Mike




31792

[JohnHaine]

Bizarrely the lathe motor has delta windings and the mill head star!

But the real question is what the winding config is on your new motor. Is there a connection cover you can remove and get a photo of it? If it can be easily converted to delta then the neutral, the place where all the windings are connected at one end at the centre, would be accessible at screw terminals and/or have links.

The rating plate says it's 0.45kW 2-pole (2800 rpm) and 0.3kW 4-pole (1400 rpm) so a VFD rated at 750W (0.75kW) should be fine.

Fitting a VFD it is best to scrap all the switchgear between the VFD and the motor, you shouldn't be tempted to switch the motor when running with an existing contactor, it will instantly blow up the devices in the VFD. All the control can be done by the VFD - start/stop, speed, reverse, soft start, e-stop etc. Just need an isolating switch and filter where the mains comes in, and a control pendant.

I've fitted 3-phase to a couple of mills using standard delta motors with ordinary VFDs and also fitted a Newton-Tesla pre-packaged unit to my Super 7 - but I haven't any direct experience of 2-speed motors. It can't be that hard though. With a VFD I doubt you would want the 2-speed feature anyway as the VFD does it for you.

I have heard that these people are very helpful: https://inverterdrive.com/

[m_c]

2 speed motors are rarely dual voltage.

You can run a 380V motor from a 240Vout VFD, but you lose torque above 27Hz (IIRC! -Inverter Supermarket have a blog article explaining it) as the motor enters into constant power, rather than constant torque due to the restricted voltage.

However, 'boost' VFDs are not that expensive or rare now. I've personally used a few CNCWeiken boost VFDs - https://www.aliexpress.com/store/group/0-75-11kw/911552016_10000000324416.html
But others have used Ecogoo.

[mekanik]

Thanks John/mc
That unfortunately is a problem for me, in turning mode the VFD control would be fine but for screw cutting i really require the button arrangement. i have seen inverters were the control panel detaches and presumable could be extended with a cable and mounted on the headstock so i suppose it is possible. a rotary converter is just overkill for one machine, perhaps it's back to getting the single phase motor repaired.
Does the £700 sound excessive for a rewind ?
Thanks again Guys.
Regards
Mike

[mekanik]

as you can see no terminal connections.
any ideas on how you would connect to the VFD ?
MC if you get time could you possibly send a picture me of your control system, no rush i still have to fathom a mounting arrangement fot the motor, it doesn't have the usual flange mount.
Regards
Mike





31793

[m_c]

I'd probably wire it up to make use of the low speed, then set the VFD to allow a higher frequency to get the high speed back.
With the correct VFD, you can configure it to allow the use of a Jog button.


Out of the three boost VFDs I have, one runs my rotary converter, one runs a basic saw, and the other is destined for my big mill which is very slowly getting bits added to it, but will likely be getting controlled via ModBus.

[mekanik]

Have been watching Youtube this afternoon and apparently the Delta arrangement allows the motor to run on 220/250V.There was a guy had a system of using the original switching, but i will have watch that a couple more times to get my head round it.
Also fathomed out the rather strange motor mounting arrangement.
Regards

[JohnHaine]

700 sqids could buy a brand new 3phase motor and vfd!

[mekanik]

Please excuse my ignorance, but can you tell from the motor nameplate IF this is infact 3 phase ?.
The guy in the Netherlands said motor was strong on 380V no 250.
I have been assuming(a bad thing to do with electrics) because of the 380V that it was 3 Phase.
Is there anyway i can check it with a multimeter, I will also need to identify the high & low speed windings, as it's looking like i will be running single speed for the imediate future(just desperate to get it making chips again)
PS that would have been £700 +VAT
Regards

[JohnHaine]

Hard to make much of the photo as some of the leads seem to be labelled with their colours and some with something else! Could you possibly say what the labels say on each lead with its colour? - that might be helpful.

There seem to be 7 wires on a 3-phase motor, so I would guess that one, possibly the green/yellow one, is ground and connected to the frame - easy to check. I don't think there could be 7 wires on a single phase. The reason why 380v is associated with 3 phase is because that's the phase-to-phase voltage, which corresponds to 230v phase-to-neutral. Your home single phase supply is usually one phase of a 3 phase supply with a neutral.

That leaves 6 more wires. Measure the resistance between them in pairs. If you are lucky you will get 3 pairs that look nearly shorted but each isolated from the other two. That would mean a simple 3-phase winding that you could easily connect in delta to run on 230v but since the plate indicates dual speed then probably not so lucky.

The only other thing to do is measure all the resistances from each terminal to the other 5 - not so bad , I think there are only 15 measurements to make. From those we might be able to figure out how the windings are configured and which wire goes where.

[mekanik]

Thanks for that John, I think i might have been clutching @ straws with this it actually came with a mains plug and that's 5 pin.
I reinstated the single phase switchgear so i get my mill attachement working and the single phase switch is different from the one supplied with the new motor.
I will try and fathom out the 2 sets of windings from the switch assemby.
Thanks again John for your time and patients.
Regards
Mike

[mekanik]

Sorry about the slight delay with the winding readings, was trying to get the motor mounted yesterday and discovered a slight problem.
John
The labels on the motor leads were only to identify the connection to the switch terminals, the issue with the cable colouring is due to what appears to be some form of insulation coating that has discoloured with the passing of time.
Readings as follows.

V4 Blue to V2 White 85.4 Ohm
V4 Blue to U2 Yellow 47.0 Ohm
W2 Green to W4 Grey 85.4 Ohm
W2 Green to U4 Red 49.4 Ohm
U4 Red to U2 Yellow 85.4 Ohm
W4 Grey to V2 White 46.5 Ohm


31806

[JohnHaine]

What you have I think is a Dahlander connected motor.

https://en.wikipedia.org/wiki/Dahlander_pole_changing_motor

https://en.wikipedia.org/wiki/Dahlander_pole_changing_motor#/media/File:Dahlander.svg

I think to run in low speed mode you connect the 3 phase wires to U4, V4, W4. For high speed U2, V2, W2, and connect together the suffix 4 terminals. Both ways the motor will expect to see 380v for full power so will give lower power at 230v.

And is the 7th wire connected to the frame (i.e. ground)?

[mekanik]

Thanks for that John, very helpfull.
Is there a prefered speed, ie high or low speed as its looking like i can't use the original mechanical switch.
Can i assume that the three phase motor even on the low power will be similar to the power of the original single phase motor.
Thanks again John
Regards
Mike

[JohnHaine]

What speed was the single phase motor?

[mekanik]

original motor was 2 speed, change over sequence was start on low speed and then press the double speed button 1400 & 2800 rpm
When i was looking @ inverters i searched for "220V single phase to 380V three phase and did find a couple.

[JohnHaine]

According to the motor plate the power is larger at 2800 than 1400 so if power is what you want use 2800, i.e. the "pseudo star" connection (second option). I couldn't comment on how the power would compare to the single phase motor since I don't know what power that was. However if you run the motor on 230v rather than 380v you will get lower power than the plate rating, but I believe that you can recover the torque by reducing the frequency to around 30Hz. If you can get a 380v inverter of course it won't be a problem.

Just to emphasise, my connection recommendation is based on what I can make out of the motor plate and the Wiki article, though I've used VFDs in several machines I haven't seen a Dahlander-connected motor and I don't remember it from my electrical machines course (but that was 53 years ago...).

[mekanik]

Thanks John
If i wire it for 2800 rpm would it be possible to reduce the speed down to 1400 without it stalling, to be honest i usually only use 2800 for centre drilling small holes and any polishing.
Does the cable comming from the VFD to the motor have to be shielded as i don't want them next door complaining when i use the machine.
any recommendations for cable size.
I wasted a lot of time trying to get the motor mounted but couldn't do it without a radical re-arrangement so i removed the end covers and swapped them with the one's off the single phase motor and there's a slight mod to do but it's only a matter of some pieces of angle iron(body of the three phase motor is shorter than the single phase)
Thanks again John,
just have to hope that the motor is OK.
Kindest Regards
Mike

[JohnHaine]

Hard to say if it would stall at the lower speed, that's more a function of torque than power. Just change the pulley ratio surely? But you can vary the speed with the VFD of course.

Ideally you need 3 core screened cable. The current won't be particular high so anything rated at 5A per core would be fine I'd guess. There is debate about how to connect the screen but for RF the screen should be firmly grounded to the E terminal of the VFD at one end and to the motor casing at the other. If you can't get 3 core screened then electrical suppliers sell 4 core cable for 3 phase one of the cores being for a ground.

[m_c]

Personally I'd probably wire it for low speed, then overspeed it via the VFD.

You could wire it for highspeed then run it slower from the VFD, but you won't get as much torque at the lower speeds.
From the plate details
0.45KW at 2800rpm is 1.53Nm
0.3KW at 1400RPM is 2.05Nm

Using the high speed windings, you'll have 1.53Nm from 2800rpm down to probably a few hundred RPM. This depends on VFD ability, motor performance, but it'll reach a point where the motor will noticeably lose performance and likely become noticeably rough.

Using the low speed winding, you'll have 2.05Nm from low speed to 1400RPM. Due to the lower rated speed (the two speed essentially works by selecting 2 or 4 pole operation), the motor will also be capable of being spun slower before performance becomes an issue.
From 1400RPM to 2800RPM, the power output will remain limited at 0.3KW which means the torque will gradually reduce from 2.05Nm at 1400RPM down to 1.02Nm at 2800rpm.


However, if your main use was in the higher speed range, then wiring it for the higher speed range would make more sense to get the most power.
Off course, you could add a changeover switch, but you'd have to ensure you don't switch it with the motor powered and spinning.

[mekanik]

mc

Thanks for taking the time to reply and your power calculations.

I contacted motorsandinverters and quized them about the 380V on the motor plate and they said a 220V inverter drive would not work with the motor, they offered a static converter @ £1100+VAT and said that would do but from what i understand as static converter supplies 2 phases, and the proper way to do it is with a rotary converter. so back to square one.

If i took some readings of the original single phase motor would you be able to determin which of the coils is damaged, and if the low speed coils are OK i could disconnect the high speed coils from the switch.

The motor actually run OK it was just the fact that it was getting hot that made me investigate.

[JohnHaine]

Ask Inverter Drive Supermarket. They have a (rather poorly written) application note on 230v running. The people you spoke to want to sell you a static converter. They also have 230v 1-phase to 380v 3-phase units. "Static" converters are yesterday's technology. (Actually a VFD is "static" but generates proper 3-phase.)

[mekanik]

Thanks for that John
I had seen 230V to 380V three phase VFD's advertised, just as well i came in for brew i was about to swop the motor covers and rotors again and commence on a box to send the single phase motor for a very expensive rewind.
was on a forum yesterday and some guy in the US added a stepup transformer before the inverter then bought a 440V to 440V VFD apparently that worked and i have seen another US made inverter that does the conversion from 220V to 440v.
Will contact Inverter Drive Supermarket
Regards
Mike

[mekanik]

deleted

[JohnHaine]

Found this on Amazon
https://www.amazon.co.uk/Inverter-AT4-1500X-Variable-Frequency-Controller/dp/B0892L6CZM

[mekanik]

Found this on Aliexpress
the video shows the chappy with a meter 220v input and outputting 410V so should be good to go, the feedback is good as well, downside being the month or so shipping plus my last purchase from Ali never arrived.would be nice to put this disaster to bed.
Kindest Regards
Mike
https://www.aliexpress.com/item/1005003013788676.html?spm=a2g0o.productlist.main.1 3.2f0520f7AfPwSp&algo_pvid=ea69ed2f-2ef6-4409-8782-0b3822ea0d8b&algo_exp_id=ea69ed2f-2ef6-4409-8782-0b3822ea0d8b-6&pdp_npi=3%40dis%21GBP%21159.29%2179.64%21%21%21%21 %21%40211bda9b16819913498757791d076c%2112000023233 497281%21sea%21UK%213550744364&curPageLogUid=CBSN0q3HLTrF

[m_c]

https://www.aliexpress.com/store/group/0-75-11kw/911552016_10000000324416.html

It's worth going through the different listings, as I've see different delivery options amongst seemingly identical VFDs.

Other make to search for is Ecogoo.

[rnr107]

Why go 3 phases ? for such a small motor the cheapest and easiest option is to buy a new single phase motor...
fairly cheap on eBay.
Unless this motor is of a special form factor or something ?

[mekanik]

That's the problem, the motor is about 130mm square and is fits behind the gearbox.
These motors are no longer made and second hand ones very rarely come up for sale, I did find a 3 Phase motor from the Netherlands(ebay) so jumped on it.
Not even sure if it works yet(waiting for VFD and other bits and bobs from Ali)
If the motor is no good i will indeed try and find a suitable 3 Phase dual voltage motor, but it could be a bear if it's much larger than the original.

[m_c]

Given those dimensions, you could probably fit a servo motor.

[mekanik]

John/MC
Hi Guys
Just an update on my lack of progress, ordered the VFD/screened cable/Fan/Potentiometer from Aliexpress.
When I had a look @ the manual for the VFD it stated that it required a 5K Potentiometer (I had ordered a 10K) so had to order a new one, tried to do something similar to Clough42 (James on YouTube) so sourced a breaker and fuse holder off e-bay. Had a problem trying to secure the secondhand 3 phase motor due to the strange mounting arrangement, but as luck would have it the motor end covers off the single phase motor actually fit the main body of the 3 phase motor so one job sorted. Not having much of a clue regarding the fuse requirements I got a couple of 10A and 20A Quick Blow fuses, pottered around making the cables up and eventually got round to connecting everything up to the high speed windings. Turned on the power and the fuse holder illuminated red then the fuse (10A) blew, tried another 10A same/same.
Installed a 20A this time the red light on the fuse was not illuminated wound up the potentiometer and the motor actually ran(now @ 50 Hz) the problem was that it didn’t seem to be running as fast as I thought it should, I assumed 50Hz per second should have produced 3000 RPM but I don’t think it’s anywhere near that, and I have no way to check it. Went into the menu and managed to increase the frequency to 200Hz and this did increase the RPM, tried to take it to 300Hz but didn’t run very well and would initially run up but then stalled. Had some problems trying to get it back to factory settings but the factory reset didn't work so could not drop the frequency back to 50Hz, after some time in the setup I managed to get it back to 50Hz, but I don’t know if the VFD is damage or the motor is just US.
Just by accident itouched the EMI filter body and got a shock, checked the voltage on the filter output and it was about 750V. disconnected the leads to the VFD and the output from the EMI filter was back to 240V. connected back up to the VFD and this time ther was an error code E5VC1. came back after a brew and this time it had an error code of E0C3.
Had a look today and the error code has cleared and managed to bget the motor running at low speed as before, so it's looking a bit sick.
Had a look online and seem to have found a motor that might be suitable.
https://www.ebay.co.uk/itm/114122298139?_trkparms=amclksrc%3DITM%26aid%3D7770 08%26algo%3DPERSONAL.TOPIC%26ao%3D1%26asc%3D202207 05100511%26meid%3D4ab85ac442824c7e9490512aacf9e3c5 %26pid%3D101524%26rk%3D1%26rkt%3D1%26itm%3D1141222 98139%26pmt%3D1%26noa%3D1%26pg%3D2380057%26algv%3D RecentlyViewedItemsV2%26brand%3DTEC&_trksid=p2380057.c101524.m146925&_trkparms=pageci%3Aab6f89dc-137c-11ee-b0e0-9a89be38b224%7Cparentrq%3Af392d69a1880a44e01d06954 fffd40ba%7Ciid%3A1
There are 2 speed options 1500 and 3000 RPM.
I really only require the 1400 and 2800 of the original motor, what would be your opinion of the best motor to go for, will the 1500 motor be able to go upto 2800, i would be going for 0.75Kw so a bit more power that the original motor.

Regards
Mike

[mekanik]

I have installed the second hand motor but it is not ideal seems to run out of puff at higher revs so have deceided to get a nice new, had problems with the inverter from the get go and will be replacing that also. at the moment i have the machine operational via the inverter front panel and i am making the remote switching arrangement. at least i can use the machine now until i install the new kit. the second hand motor was a bad idea in hindsight. thanks for your comments.
Regards
Mike

[JohnHaine]

The motor you linked to is single phase so wouldn't work with an inverter.

If you are going to buy a new motor and inverter I strongly suggest that you contact Newton Tesla and get their advice on which of their motor/VFD packages would best suit your needs. Though I did my own install of a 3ph motor and inverter on my mill, when it came to my Super7 in the end I just bought their package and it worked without issue.

Or fit one of the modern brushless servo motors/controllers made for industrial sewing machines. Look up "Jack Sewing Machine Motor" on eBay. Quite a few people have used these and recommend them for mills & lathes.

[mekanik]

My bad John, i just did a quick paste of the type i had been looking @(size wise) will need to do some mods to the fan location on the new motor ie mounting it on the drive end as per the original and i should be able to get a fixing off the flange to allow me to fit the original belt guard. will check out Newton Tesla and see whats available. did look at the sewing machine motors originally then got sidetracked when i found the second hand Emco motor.
Been an expensive journey,but when i get my remote controls sorted the second hand Emco motor will give me an operational machine, and the stress levels have dropped considerably in expectation.
Regards
Mike

[m_c]

It sounds like the inverter isn't configured correctly for the motor.

Personally, given the space limitations, I'd consider fitting a servo motor and drive, as you get a lot more performance in a smaller size.

[mekanik]

The VFD was damaged in trasit so i think a new one would be required if i went with a new motor, unfortunately when it arrived i had a quick look at the user manual and it stated that it required a 5K resistor for the speed control, i had ordered a 10K so by the time a replacement arrived i was out of the free return option. when i did turn it on some time later it blew the quick blow fuse i had installed, bit of a weard one really, i would have axpected a sharp pop imediately i closed the breaker but it sort of fuzzed a bit before blowing, there was an integral LED in the fuse holder and it blew that as well. i checked the output from the VFD with the motor running and it was jumping arround (500/750V) it should be outputing 380V but i now very little about these things, it won't accept a frequency greater than about 300 and if i try to run it at that the motor just runns down, maybe a phase is down.
What's involved regarding the servo drive and specifically the control of same considering my illiteracy in the electrics department.
Thanks for you c omments.
PS forgot to mention i got a shock of the setup(just toucked the line filter case by accident) checked the voltage on the filter output and it was reading about 750V. disconnected the leads to the VFD input, checked the filter output and it was back to 240V. when i reconnected the vfd gave an error code. the following day i turned it on and got a different error code
a day later when i tried it it seemed to have fixed itself(ish) and thats the state of play at the moment.(seller not responding)
Regards
Mike

[m_c]

It would likely still have worked with a 10k pot.
Even quick blow fuses, only trip fast if they see a big enough current. There are blow speed charts, which show that if only slightly above their rated current, they may take a few minutes to blow.
The big difference between quick blow and slow blow, is the slow blow allows for an immediate in rush of current without blowing. Over a longer period of time, they act similarly to quick blow.

Measuring the voltage wouldn't likely yield an accurate result with a standard multimeter, due to the switching nature of the VFD output (multimeters are typically designed to measure pure sine wave AC, and the high frequency switched quasi-AC output from a VFD can cause them to read high or low depending on the multimeter input filtering circuit).

If you were to switch to a servo, if you want to control the speed manually, then you'd need one with a drive capable of accepting a +/-10V input (most do, but some cheaper ones are digital input only, so best to get a manual for the drive to check), and some way of generating 0-10V (10V supply and pot, or 12V with an additional resistor in series so the Pot only gets 10V).
Or if you want to control it via software, you can just wire it to make use of step/dir (or CW/CCW or quadrature depending on your controller).
And to give an idea of the compactness, 400W and 600W servos can be had in 60mm, or 400W and 750W servos in 80mm frame size. The frame size being the overall size of the front mounting flange.

To give an idea of servo cost-

Lichuan A5 drive with choice of 200-600W 60 size servo - https://www.aliexpress.com/item/1005005440028771.html
Lichuan A4 drive with 400W 60 size servo - https://www.aliexpress.com/item/33049594917.html
Lichuan A4 drive with 400W 80 size servo - https://www.aliexpress.com/item/33050955694.html

The difference between the A4 and A5 drives (and motors), is the A4 uses an incremental motor encoder (outputs your classic AB quadrature), whereas the A5 uses an absolute (17bit) motor encoder. In terms of functional difference, there's not really anything notable.