3 phase motor connection plate

   Hi all

having recently purchased a warco A2F mill 3 phase I was hoping to convert it to run on a vfd. The motor plate doesn't state that it is dual voltage however there are six cables coming from the motor labelled up as U1 U2 V1 V2 W1 W2, the wiring diagram on the plate shows the connections as shown on the photo. In its standard guise it is a two speed induction motor Could anyone advise me if this is a dual voltage motor or not, many thanks in advance

Edited By John Templeman on 27/10/2022 18:39:21

NO, it's strictly single voltage. See here for details;

Cheers Mark, not really what I wanted to see but at least I now know for definite, oh well back to the drawing board lol

John

Edited By John Templeman on 27/10/2022 19:52:01

Whilst everybody thinks of VFDs for 3phase don't forget the 3Ph converters, the likes of TRANSWAVE Etc Noel

Well I've used an inverter/VFD to generate my 415V 3phase for a long time now, but there's no point me blathering on about it because the received wisdom seems to say that it's impossible/unsafe/immoral/blasphemous etc.

Buying a RPC is cost-neutral with a 240-to-415 VFD for the first machine...

But for machines 2 to n+1 the phase converter costs nothing, I am very happy with my Transwave (recently purchased second-hand to replace my home made Converter) and am confident that it made more financial sense.

A static converter has some drawbacks by comparison to a rotary one, but could work out cheaper than a VFD altogether second-hand due to being unfashionable.

.

If John is intending to buy or open to buying additional 3-phase equipment I would recommend a phase converter over spending hundreds on a VFD conversion on each successive machine.

If you want to, you can run it in one configuration and treat it as a single speed single voltage motor since a VFD will allow changing the speed. You have not stated what the supply voltage is supposed to be to know which configuration suits a basic 240V VFD best.

Martin C

You can connect it for lower voltage by wiring it as double delta. I.e. each pair of windings in parallel and keeping the delta connecton HOWEVER, the voltage will not be the same as changing star / delta in a single speed motor. The single speed star/delta ratio is Sqt3:1 = 1.73:1 ie 415V / 240V.
For double delta the ratio will be 2:1 so if it is a 415V motor it will need 207V to run properly. Many VFDs will allow you to adjust the voltage e.g. by adjusting the V/F ratio away from normal.

Robert G8RPI.

If John intends to buy other 3Phase machines [easier to find 2nd hand ], a Transwave rotary converter might be the best way to go. I bought one some years ago, when I moved to the sticks, and it runs all my 3Phase gear, often two or three machines at the same time [when pals come to "help" ] It,s much easier than running around from one unit to another, just switch on and power the lot, no need to be tweaking this or that. Plus, 3Phase is so much smoother.

Just my experience.

Note that "rotary" converters are inefficent, noisey and not as "smooth" (unless a genuine motor-generator) as a VFD. And you can't change the speed.

Then there is the cost. A 3kW Transwave RT is about £1000 and has a MINIMUM single motor load of 2.2kW. So you can't use it to run a single machine less than that. It's a 2.2kW alone or 2.2kW and up to 800W. That is not "run anyting in the shop". I'm sure lots of people will say " I run a single x.x kW motor as a single load without problems". That may be but it's outside the specification. You can buy at least 5 1.5kW VFDs for £1000.

You can set and forget a VFD for single speed and just have start / stop buttons.

Robert G8RPI.

Robert makes an excellent point about relative costs of a new commercial rotary converter relative to several VFD boxes. As he says break even costs for a new converter against new branded VFD boxes is probably around 5 or 6 machines. Rather more if an unknown name import from a box shifter is acceptable.

For minimal complexity if you don't need the infinitely variable control of a VFD, a feature rather more attractive in theory than practice in my view, I like the Eaton DE1 series. These are made as a replacement for old style contactor controls and are about as close to drop in as can be. Just find somewhere inside the machine stand for it. That said I'd probably set up as a two speed device to, for example, halve the steps between belt positions on a lathe.

Going back to Johns motor it only has 6 connections so cannot be set up in double delta with windings in parallel. Doing so would reverse one of the windings in relation to its parallel connected mate which isn't a good thing. You need 12 connections, one for each end of each winding so the windings can be correctly paired and phased. Despite knowing how its done that's not something I'd care to try as its very easy to get in a mess.

Clive

Edited By Clive Foster on 28/10/2022 10:20:32

I have a couple of points:

1. If the Transwave product you were looking at had a minimum motor size, then it's a static converter, not a rotary. Those can actually run smaller motors, but only if a large one is running on the same circuit, so for coolant pumps etc, it's not the end of the world.
2. I specifically compared payback to purchasing on the used market because converters are durable and long lasting machines with a service life of 30+ years, if you're concerned about cost it would never make sense to purchase new, but buying used is rarely any different due to the nature of the machine.
3. In the context of a workshop I have never found rotary converters to be noisy, yes they do create a bit of a hum, but compared to taking a serious cut on any machine tool, drilling, welding, grinding, rivetting or hammer forming, the sound doesn't touch the sides.

When I looked at replacing the system in my workshop recently, I found myself needing 5 VFD's between 0.35kW and 4kW. To do that would have  seen me spending significantly more than £1k on the VFD's, and having to do a major rewire of the control circuitry on my lathe, then having buy several other new components for the privilege of installing my VFD's...

Vs paying £380 for a 7.5kW Rotary Converter which was about 5 years old with low hours and documentation showing it hand been serviced by the manufacturer before it went into storage, which has been plug and play.

VFD's are fine and all, and have their advantages, but my experience is that they're not the only viable solution, and may not be the best solution for all use cases.

Edited By Jelly on 28/10/2022 10:57:19

I must say my experience has been much the same as Jelly,s, except that my converter cost me a LOT more !

As he said, there is no minimum load, this is confirmed by the paperwork I received with the unit, and surprise, surprise, it does run everything, just plug in and go !

I did try a static converter early on [ it was on loan to me to try it out ], but I found it to be useless to run my wood planer or spindle moulder, although it was a fair sized unit.

Would be nice if the second hand market here was a bit bigger and better, but that,s not going to happen any time soon, and trying to get anything from England now is a P-I-T-A. !

Jelly,

you are correct I misread. There is no minum load on the rotary. Sorry about that.

Robert G8RPI.

Hi All,

Many Thanks for all your input it was interesting to read all the points of view and I can really see the advantage of a rotary phase converter, however as I don't intend adding any more machines to my workshop I think it would be more cost effective for me to use a VFD to power the mill. Could someone advise me on what would be the correct cable connections to allow me to do this. The cables are labelled up by the motor manufacturer as U1 U2 V1 V2 W1 W2.

John

John

Basically you can't simply convert to low voltage delta to use a VFD.

As drawn the plate shows a two speed 440 volt motor. Changing between delta and star merely alters the speed.

To connect in double delta to run off a normal 220 volt VFD, as described earlier by Robert, you need access to all the 12 ends of the 6 windings. Realistically that is a job for a professional who knows how to make sure the windings are correctly orientated. If all the wires do come out to the terminal box its pretty simple for a pro who has experience in such things. 15 minutes perhaps so if there is decent rewinder locally it might be worth asking.

Clive

I'd give Newton Tesla a ring and see if they will reconnect it and supply a vfd as a package.

Would it not be possible to use on of the import VFD's s that is 220v in 380 v out ?

Look in the phone book to find your local rewinders and take the motor to them, they will know what to do. To much irrelevant info on here for safety.

Running a motor on a VFD at less than the nominal voltage required simply reduces the speed at which things go into constant power mode iwth a pro rata reduction in power at the rated speed. I suspect that for most of us with industrial workshop sized machinery the loss of power will not be noticed. We generally just don't drive large cutters or large work at high speeds. If we do go fast its usually a small cutter or small job so inherently needing less power.

As usual Inverter Drive Supermarket explain running at less than norminal voltage is a way that normal folk can understand.:-

**LINK**

https://inverterdrive.com/HowTo/240V-Supply-to-a-400V-AC-Motor/

Clive