Newman 3ph motor help

[rich webbParticipant @richwebb63776]

Hi all.

Newbie here so please be gentle! I recently picked up a raglan mill from a lovely chap in Yorkshire. The mill is 3 phase and he had been running it on a phase converter.

I assumed (I know!!) That I could just buy a vfd and run it off that, but it hasn't proven to be the case.

The motor itself is a Newman 3 phase. It is connected to the supply via a switch which provides 2 speeds, and an isolation type switch.

I initially connected the VFd to the 3 phase plug, however apart from some humming, no dice.

I've removed the motor, and noted it has 6 wires coming into it's connection box. Every wire has continuity with every other wire, showing either 50 ohms or 90 (ish).

I have now wired the vfd to the speed selection switch, which, when the VFd is powered, spins the motor at different speed depending on the switch position. Great! Problem is that the motor has no torque at all. When the mills belt drive is connected it cannot even overcome that friction and spin the spindle.

I have done some research on 3 phase motors, especially the very helpful guide just below this one, where the author converted his Newman motor from star to delta. Difference is that his Motor has three wires to my six.

Extensive googling has yielded nothing which gives me confidence!! Can anyone point me in the right direction to get this machine running?

[rich webbParticipant @richwebb63776]

[rich webbParticipant @richwebb63776]

[Ian ParkinParticipant @ianparkin39383]

I’d just buy a new(sh) motor 4 pole of at least 375watt (1/2 hp) or bigger if you can squeeze a bigger one in

make sure its dual voltage

i bought 2 last week on eBay for £40 each both new and unused

[Chris Pearson 1Participant @chrispearson1]

It would be more useful to see the motor's terminals please.

The 6 wires will be the ends of the 3 coils. You need to ensure that you have the motor correctly wired in delta or star as appropriate. What do the VFD's instructions say?

Edited By Chris Pearson 1 on 15/02/2023 18:42:22

[rich webbParticipant @richwebb63776]

Thanks for the message. I did consider that, but The motor lives inside the mill body, and the information I found on the raglan says it's extremely difficult to find an alternative motor which would fit.

[rich webbParticipant @richwebb63776]

[rich webbParticipant @richwebb63776]

[rich webbParticipant @richwebb63776]

Please excuse the crudeness of the drawings!!

The numbers in the grid indicate the resistance between those points in ohms

[old martParticipant @oldmart]

3hp or 1/2hp as the motor plate indicates? With the lower power motor, you would be best advised to get a new motor. The mounting and spindle would probably be different so it would not be a straight swap with the old one.

**LINK**

[Martin ConnellyParticipant @martinconnelly55370]

It is a 400 volt (phase to phase) motor but it is likely your VFD puts out 230 volts (phase to phase). You can get one that puts out 400 volts but they cost more than the usual cheap options.

Based on wiring diagrams I have seen for 2 speed 3 phase motors the coils require 230 volts across them. However there are six coils with 12 tails and separating them then linking some to give six tails to enable the correct wiring for a 230 volt VFD looks daunting.

Normally the VFD should be connected directly to a motor and it is recommended to not disconnect a powered up VFD from its motor by passing it through any form of switch.

Martin C

[Clive FosterParticipant @clivefoster55965]

It's a two speed constant torque motor, almost certainly of the Dahlander pole changing variety, so sorting out the windings and connections is likely to be challenging. Especially if you've not done that sot of thing before.

Objectively the simple way is to feed it proper three phase, whether from property set up rotary converter or a 440 volt output VFD run at a fixed 50 Hz, which will be a close facsimile of what it was designed to run on. It's possible the the relatively inexpensive import 380 volt output VFD boxes will be capable of running this motor on both speeds if set to 50 Hz but by their very nature such devices have performance limitations. Primarily due to the love DC bus voltage.

If you are determined to disentangle things it's advisable to have a reference diagram for how the motor wiring and switch gear is connected. Presumably you don't have a diagram for the Raglan. The two speed motors used on 2 1/2  hp Bridgeport J heads do bring out all the wires which can be re-assembled by the electrician if the factory connection is disturbed so the necessary information is on the Bridgeport wiring diagram. In rather less than crystal clear fashion! Maybe someone knows of a better source for the machine – motor connections.

About 5 years ago I answered a similar question, relating to running a two speed  Bridgeport motor off an ordinary 220 volt VFD, so I have cut and pasted the relevant text.

——

The common Dahlander connection two speed motors cannot be run off an ordinary 220 V output VFD because they don't have alternative low voltage (220 V) Delta and high voltage (440 V) Y connection capability. They require 440 V input for both speeds with the coils laid out Delta style for low and Y style for high.

There are six windings in the motor. For low speeds the windings are connected in a series loop with power applied to every other connection. So 440 volts is applied across each pair and the individual windings see 220 volts each. For high speed the windings are connected in parallel pairs. One end of each pair goes to a common point the other end receives power. So each winding sees 220 volts.

You can run a Dahlander motor in high speed setting off a 220 V VFD by connecting the windings in parallel pairs and running them in a series loop with power applied to each corner. Effectively each parallel pair is equivalent to the single windings on a normal three phase motor in Delta connection. Not something for the novice to try. Its very, very easy to get things muddled up with paired windings out of phase or not correctly paired. Not something I'd try. I could do it but wouldn't if you see what I mean.

Wikipedia has an adequate, albeit small, diagram of the coil layouts :- **LINK** . Google search will show up plenty more pictures but most aren't linkable. This is quite a good one showing the switching involved :- **LINK** for speed changing.

——-

its not something I'd care to fiddle with.

Clive

Edited By Clive Foster on 15/02/2023 19:41:02

[SillyOldDufferModerator @sillyoldduffer]

Posted by Ian Parkin on 15/02/2023 18:27:16:

I’d just buy a new(sh) motor 4 pole of at least 375watt (1/2 hp) or bigger if you can squeeze a bigger one in

make sure its dual voltage

i bought 2 last week on eBay for £40 each both new and unused

I agree, unless someone comes up with a clever answer. With luck a Raglan owner will have sorted this out before, but I fear the worse.

VFDs are easy peasy unless:

• The motor is star wired internally for 415V 3-phase, with no way of switching to delta apart from opening the motor up and finding and separating the connection into pairs. It's usually possible, but it looks as if the motor also features the other anti-VFD booby trap which is
• The motor provides two speeds by having two sets of windings, selected by external switches. Not an ideal method when the motor was made in times of yore and I think unlikely to be done today. The usual method now is to speed control a standard single speed motor with a VFD, which has several advantages.

Looks like this particular motor has both problems; star wound and 2 sets of windings, plus an unusual size, which is why the previous owner ran it off a phase converter. Maybe he can explain his converter, and you can copy it.

Hope I've got it all wrong and my gloom is unjustified.

Dave

 

 

Edited By SillyOldDuffer on 15/02/2023 19:40:14

[noel shelleyParticipant @noelshelley55608]

I would do as the previous owner and use a converter, I would check wether static or rotary. You have a good motor designed for the job. Otherwise you will have to alter and may be ruin the motor, and possibly have to rewire the switch gear for what ? VFDs are good for some jobs, but I'm not sure this is one of them. Noel

[Pete RimmerParticipant @peterimmer30576]

I had a 2-speed Newman motor which had two entirely separate windings for low and high speed, so it may well be a Dahlander connected motor but eqully it may not.

Rich: Have a look on the inside of the motor terminals cover there should be a connection diagram.

Edited By Pete Rimmer on 15/02/2023 20:22:54

[rich webbParticipant @richwebb63776]

Thanks to all for your advice. Very helpful (if not what I wanted to hear!!). Pete Rimmer, I'll post a photo of the connection box tomorrow. I can say there is definitely no connection diagram inside. All there are are 6 posts, labelled as the diagram above.

I think I could just about manage to find a star connection inside a motor, but locating and isolating all the coils is well beyond what I think I could do. Certainly it's a foolish guy who asks for advice and ignores it!!

I'll look at motor replacement, but it's such a tight fit in the mill I think I'd be very lucky to find one which fits, and as Noel says, I have one which is designed for the job, I just need to feed it!

I'll research phase converters. Annoyingly, I can't see that I'll be buying more three phase tools (already have a lathe) so a rotary converter seems like it wouldn't get enough use to justify its considerable cost.

[Pete RimmerParticipant @peterimmer30576]

Looking again at your resistance figures your motor IS a Dahlander connection one. Typically you would have six wires out to the pole changer switch and the three that will form the star point and 3 that are in the middle of the straights will have approx. 2x the resistance of the other combinations.

Here is a typical 2-speed reversing pole changer arrangement. In low speed the power is sent to the three corners of the triangle, in high speed the corners are connected together and power is sent to the nodes in the middle of each straight side.

In the image above if you count the contactors 1-7 from top down:

1,2 and 7 switch in high speed (1 and 2 providing phase reversing)

3,4 and 6 switch in low speed  (3 and 4 providing phase reversing)

5 creates the star point, when high speed is selected in either direction.

Edited By Pete Rimmer on 15/02/2023 21:23:15

Edited By Pete Rimmer on 15/02/2023 21:33:27

[Chris Pearson 1Participant @chrispearson1]

I would expect to find 3 links in the terminal box. They could go A2-C3, B2-B3, C2-A3; or A2-B2-C2 and the supply cables would be to A2, B2, C2.

Are those resistances with all the terminals independent, or with links installed?

[rich webbParticipant @richwebb63776]

Hi Chris

You're exactly correct on the labelling of the wires from the motor. I don't have links, but do have a large rotary switch (which I think is the contactor which Pete is referring to). That switch I suspect will change all the connections around internally to achieve what Pete suggests.

So next question, and I'm talking myself into something unwise.

If my motor is wired delta (albeit dahlander delta). Surely what I would need to do is open it up and each wire emerging from the casing will be connected to two coils. I split those coils at that point and add wires, bringing twelve wires out and having access to all windings? Am I being over simplified? My main concern was locating the join points, but if the wires emerging from the casings lead me to them, that may be achievable

[Pete RimmerParticipant @peterimmer30576]

Rich,

I have done exactly that thing. It's no trivial exercise but it does work to yield a 240V delta-wound motor. How successful it will be in operation is unknown for me I do know that the motor runs on a VFD but tends to whistle a bit.

Pete

[DC31kParticipant @dc31k]

I am a little puzzled why you would want to go to the trouble of converting it to low voltage three phase when 230v single phase input to 380v three phase VFDs are now so cheap and easily available. Search for 'AT4-2200x VFD'.

Clive's point above about the output of the devices being a compromise is true but only has any real force if you are trying to drive a motor near the stated capacity of the VFD. The AT4 is a nominal 2.2kW device, so it will have no problem driving a 1/2 or 1.4 hp motor – you are derating it by a minimum factor of four.

Set the VFD parameters to suit the 1/4hp mode and try it. If you get too many overcurrent faults in the 1/2hp mode, you might have to adjust them upwards and go gently in the other mode.

Pick the equivalent 230v output VFD and work out the price difference between the two. Is the time you will spend to convert to 230v three phase worth that money?

To me, you would be better spending your time thinking about a way that you guarantee that you can only change motor speeds when the VFD output is inactive (i.e. an interlock between the VFD's control circuitry and the mechanical speed change switch).

[rich webbParticipant @richwebb63776]

Hi dc31k.

Genuinely didn't know such a thing existed. It strikes me that that would be exactly the thing which I required (and thought I had with my vfd!).

Any reason why I wouldn't go down this route anyone? Seems by far the simplest solution

[Clive FosterParticipant @clivefoster55965]

Rich

In principle one of the 380 volt output VFD boxes ought to work OK but it would be prudent to buy a seriously oversize one. I'd go for 2 hp (or more) rather than matching the 1 hp motor specification. I'd also try to buy from a UK supplier, or at least address rather than direct from China as there is more chance of after sales service / technical support. Its very re-assuring if the supplier can say "Yep, we sold one that worked just fine on the same machine.".

Two potential issues.

First one is that Dahlander connected pole changing motors are notorious current hogs during run up, how much so depending on design details. No great issue with umpteen megawatts of National Grid doing the supply bit but VFD boxes and rotary converters have strictly limited current supply capability and may not have the drive capacity to bring the motor up to speed. For example the three speed 3 hp motors used on Holbrook and other older British machines are notorious for needing a 7.5 or even 10 hp phase converter to reliably bring them up to high speed!

Second one is that the 380 volt VFD boxes inevitably have a lower DC bus voltage than a proper 440 volt system along with lower full voltage current drive capability. So they can easily run out of drive on a demanding application. Buying oversize gets you more current drive capacity.

As ever its price / performance ratio issue.

These devices are fundamentally economy range units built to give a useful performance to the undemanding and impecunious user at an affordable price. I seriously doubt if any of these devices, when matched to motor size, are capable of delivering full torque and power at 50 Hz let alone higher speeds. Which much matters not a jot to folk like us who are pretty much never going to drive the ex-industrial 3 phase machine we usually hook them up to at anything like its full power. Even 1 hp can shift impressive amounts of metal!

I found out about the limitations of 380 volt VFD boxes the hard way around 15 – 20 years ago when I bought a so called 440 volt output 4 hp VFD in a very professional looking box to run my S&B 1024 VSL lathe. That machine has its 3 hp motor connected directly to the spindle via a Reeves type varispeed belt drive using expanding and contracting pulleys. The VFD proved incapable of driving the lathe at its maximum 2,500 rpm. At anything over 2,000 rpm the unit couldn't supply enough power to accelerate the empty spindle up to full speed

Internal investigation showed the nice new box to contain a second hand ABB industrial VFD with its input rectifier re-arranged to give a nominal 380 volt output in most likely the same manner as will be used on the modern imports. Reeves drives are notoriously mechanically inefficient. My drive probably sucked up something like 3/4 hp, maybe more, at top speed and the rather crudely modified VFD box was unable to provide the power needed to accelerate the machine against that much load. Careful probing around with a meter showed the drive voltage basically collapsed.

The supplier proved uncontactable so the box was sold, at considerable loss, into a less demanding application where it worked just fine for at least a decade.

I wised up on VFDs along with the difference between a fancy web-site and actual professional products after that!

Clive

[DC31kParticipant @dc31k]

Posted by Clive Foster on 16/02/2023 13:13:51:

I'd go for 2 hp (or more) rather than matching the 1 hp motor specification.

The motor in his photo is badged 1/2 hp in one speed and 1/4 hp in the other.

Given the passage of considerable time and the ongoing march of technology, how much weight should we assign to your experience of 15-20 years ago?

Your observations on Holbrook and the like could be misleading insofar as we need to consider the amount of inertia the motor is being asked to overcome and the rolling resistance of the drivetrain. It is the difference between an American muscle car and a Lotus 7.

In addition, the VFD will offer a soft start (ramp up) capability, so the initial current demand will be considerably less.

[rich webbParticipant @richwebb63776]

So, I wanted to come back to the forum to add the solution I came to in the end.

First of all, thank you all for your thoughts and suggestions. It really did help me understand the problem and options for a solution, of whic there were clearly a few!

I ended up going with dc31k and ordering a boosting vfd. It arrived from china yesterday and I got it wired in today. It allows me to retain the 2 speed motor, so I can use the switch to go to high and low speed (though I accept that the VFd will also do that, and also the raglan has a nifty system of adjustable pulleys to alter speed, exactly like a CVT type transmission).

Anyway I bought this. https://a.aliexpress.com/_mtJ5IkI

Its labelled as an he200 vfd.

Cost was £61.71 delivered to my home. Instructions were in mandarin, but the seller emailed me a link to English instructions on request.

Easily wired up, and it performs perfectly fine. With the mill set to "high speed" on the switch selector, I do have to give the spindle a quick spin to get it going, otherwise it just buzzes. Once it gets started it accelerates well and has sufficient power for what I need.

Once again, thanks to all for your advice. I'd never have got to this point without your help.

[Author]

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