Myford ML7 replacement motor.

[Glen Morgan 1Participant @glenmorgan1]

[Glen Morgan 1Participant @glenmorgan1]

My Father has a Myford ML7 lathe and he has bought a replacement Single
Phase 3/4 HP motor from Myford but is having difficulty with wiring it
in.

The motor has numbered connection points, and it came with a wiring
diagram but nothing seems to relate to original connections, and the
wiring diagram is useless.

I am reasonably good with electrics, and he has had a friend who is an
electrician look at it but neither of us can work it out. Myford are
being very unhelpful, which is very poor as it cost nearly £200-00.

Could you help with which wires should be connected to which terminals?
The lathe has its original reversing switch.

Many thanks,

Glen.

[Les Jones 1Participant @lesjones1]

Hi Glen.
Can you post a good close up photo of the wiring to the connection box on the old motor and make a list of colours/markings of the wires that come to the motor from the reversing switch and the terminal block markings in the motor. If the start/run capacitors connections are to the top side of the motor terminal block list the terminal markings that these connect to. Can you also post the information sheet that came with the new motor and a picture of it's connection box. If you live near enough to me I am willing to help. It is much easier when you can see the problem and measure resistances to identify the windings and start switch.

Les.

[Ian S CParticipant @iansc]

Glen, this is a case where a profile can be helpful, giving an indication to not only which part of the country you live in, but which country you live in, the guy who answers your question might live in the next block to you.

Ian S C

[LambtonParticipant @lambton]

Glen,

The Myford handbook has very clear instructions complete with diagrams for wiring single and three phase motors via Dewhurst or Stanton reversing switches.

Eric

[Bob Brown 1Participant @bobbrown1]

may care to try here **LINK** and there are other articles

[RobboParticipant @robbo]

Glen,

It will be no use looking in your Father's ML7 manual, as there are a new generation of motors which will differ from those illustrated, as his lathe requires a new motor.

As has been said, we really need to see the wiring of the motor and the diagram/instructions that came with it. Take some pics with the digital, create an album here and upload them, then you can put them in a post or we can access your album.

I had a look at the motor illustrated on the Myford site, and would suggest that you may need to remove the purple wire on the motor from its junction with the red wire, and fix it to a new terminal of it's own. There should be a couple of terminals not shown as wired. The one you want may be numbered "S". The other capacitor wire connected to Black will also need to be moved to the other spare terminal. If your terminals are Z2, R, S, U2, U1, P.

Then it can be connected to the Dewhurst in the normal way for a 4-terminal motor, but you may need to change the +ve wire from terminal 1 to 3, and the -ve from 3 to 1.

This is complete conjecture on my part, but illustrates what may need to be done with this type of motor. They can't be connected for reversing "straight out of the box".

We do need to see "what you have got"

Phil

[Glen Morgan 1Participant @glenmorgan1]

Thanks chaps.

My Father is away at the moment but I will see if I can get some photos and make a note of the existing wiring colours.

Glen.

[LambtonParticipant @lambton]

Glen,

As Myford do not make electric motors merely buy them in and sell them on why not contact the actual manufacturer or look on their website?

Eric

[Glen Morgan 1Participant @glenmorgan1]

Posted by Lambton on 01/05/2014 09:09:49:

Glen,

As Myford do not make electric motors merely buy them in and sell them on why not contact the actual manufacturer or look on their website?

Eric

Eric,

I think the motor is made in the far east and, as their instructions are useless, I can't imagine the web-site will be any help, if it is even in English!

Glen.

[LambtonParticipant @lambton]

Glen,

I am surprised that Myford sold your Dad a motor, presumably of Far Eastern origin, for the thick end of £200 and then could not provide any help with fitting it to Myford product – even an obsolete ML7. They took over the whole of Myford remember!

Machine Mart sell Clarke motors, made in Europe, for very reasonable prices e.g. a ¾ HP single phase for £80.39 including vat. Have a look at the spec. I have great respect for Clarke as they provided spare parts for my Taiwanese band saw purchased from Warco several years ago. Warco said it was obsolete and they had not carried spares for some years and could not provide any further help.

Over the years I have also purchased several new motors from electric motor repair companies who are the backbone of industry usually providing a very fast re-wind/repair service together with sales of new motors. Such companies are in most large towns. The one I used most is in Eastern Oxfordshire and they provide a super service. They once converted a star only 3 phase motor with only 3 terminals to delta at a very reasonable price considering the motor had to be stripped and the star point dug out etc.

So it pays to shop around and where possible support your local specialist.

Eric

[Glen Morgan 1Participant @glenmorgan1]

John & Eric,

My Dad did consider getting his old motor re-wound but apparently it went bang in a quite spectacular way, so he thought that it might well be beyond repair.

He could have looked around for another motor, such as Clarke one, but the thinking was that it would be far simpler and easier to get the one from Myford, so that it would go straight on and be easy to wire up. That has since proved to be far from true!

I spoke to my Dad yesterday evening and apparently the motor is still with the electrician who looked at it for him. He was going to get some advice from another electrician who is more experienced with industrial motors, so I will see if I can get it back over the weekend and post some photos up.

[LambtonParticipant @lambton]

Glen,

Before connecting up the new motor I suggest that you have a good look at the Dewhurst switch (or alternative) as the contacts on these can get very burnt when the switch is used as an on/off device. I have known the contacts to be welded together in some cases. These simple switches should always be used in conjunction with a proper direct on-line starter which is used to turn the motor on & off with the Dewhurst switch simple used to select the direction of rotation (whilst the power is off). Suitable starters can be obtained at reasonable prices from Clarke and Axminster.

Eric

[RobboParticipant @robbo]

Glen,

Having had a look at motors on the Myford online catalogue, these look like B56 pattern motors from BFM Sheffield.

That is "Beatson Fans & Motors", who have a website at http://www.beatson.co.uk

It's a pity Myford don't show the side with the label on it, but then of course one could buy direct.!

Phil

[stan pearson 1Participant @stanpearson1]

Hi Glen

I bought a new motor for my super 7 from Myford and it was a Brook Crompton when I had trouble with the wiring and rang them they were most helpful and talked me through it as I did it, things must have changed big stile since then,

Regards

Stan

[Glen Morgan 1Participant @glenmorgan1]

Stan,

Yes, things have changed. This one is a TECHTOP TEC and it's made in China, and Myford no longer appear to be helpful.

Glen.

[Glen Morgan 1Participant @glenmorgan1]

Right then chaps.

At the bottom of this post is a photo of the wiring diagram on the motor which is a TECTOP TEC, made in China about 11 years ago according to the date on the label, so hardly new!

The wires connected to the old motor were as follows: –

Red – permanent live.

Yellow – live from direction switch 1.

Green – live from direction switch 2.

Blue – neutral.

Obviously the colour codes for the wires don't correspond but if terminals 5 and A are responsible for reversing the direction, how can the wires actually be physically switched over as shown.

Also what is the blue wire supposed to be given that is also connected to terminal 5?

Yellow must be a permanent live or neutral.

Hope one of you can make sense of it.

Glen.

[Nick_GParticipant @nick_g]

Posted by Glen Morgan 1 on 04/05/2014 00:09:14:

 

 

Connect the incoming supply of live and neutral to 1 & 2 – e.g. live to 1 & neutral to 2 (or vise versa)

The rotation is then determined by which colours are bonded together on terminal 5

Don't forget the earth to the frame. They often omit earth connections on diagrams for clarity and presume you will automatically connect it.

Get it running in one direction or the other first to check you have not 'butchered' the motor (unlikely but possible) by previous wrong connection.

Once you have done this let us know and we can then sort out the reversing issue by use of a multi pole rotary switch by altering the connection permitations that configure 5 & A

Have you got a multi meter or a continuity tester.???? – You will probably need one to 'bell out' the open and closed sides of the switch.

 

Nick

 

 

Edited By Nick_G on 04/05/2014 05:48:25

[Glen Morgan 1Participant @glenmorgan1]

Nick,

Thanks for that. My father is back at the end of the week, so we will give it a try next weekend.

There is an earth too, so that will get re-connected with a ring terminal on one of the mounting bolts.

Yes, I do have a digital multi-meter. What I find very annoying is that an additional rotary switch is going to be needed to change the connections on the motor (I presume to switch the red and black wires over), so it is hardly a direct replacement. Why is this necessary, when it wasn't on the original motor?

With hind-sight it might have been a better bet to see if the old motor could have been repaired.

Glen.

[Nick_GParticipant @nick_g]

Glen,

Where in the the country are you.?

Nick

[Phil WhitleyParticipant @philwhitley94135]

Ok, single phase motor, to reverse you need to reverse the polarity of the start winding. The start winding is the red and black wires. You need to disconnect the red and black from the terminals and extend the two wires to the existing reversing switch, bring another two wires back from the reversing switch and connect them to terminals 5 and A, then wire the reversing switch so that it reverses the connections. I can't tell you how to do that untill I have a wiring diagram of the switch as I am not familiar with the Dewhurst type switches. If you can post it up I can work it out.

Hindsight is a wonderful thing! it probably would have been cheaper to rewind the old motor, epecially seeing as you have been ripped for the new one! I recently bought a recon motor for my compressor from a local rewinder for £60, single phase 3hp. Never mind, you have bought it now, go with it.

Phil

[Les Jones 1Participant @lesjones1]

Glen,
There are a few possibilities. I think the reason Nick asks if you have a multimeter is to be able to identify how the motor is wired internally. (I would have asked the same question.) It may be possible to change the way the motor is wired internally to make it work. Another option would require one or two extra conductors in the cable between the motor and the dewhurst switch and also some links changing on the switch. Resorting to using an extra reversing switch would be the last resort. The reason Nick is tying to find out roughly where you live is because it is so much easier for someone with some electrical knowledge so sort out the problem when they can see it first hand. There was a similar problem earlier this year that took a long time to sort out which could have been sorted in a few minutes by someone with direct access to the machine. See this thread. Does your new motor have any capacitors attached to it ?. (There may be either none , one or two.)

Les.

[John Stevenson 1Participant @johnstevenson1]

Sorry but I have to stand up for Myford on this one.

 

They have supplied a motor with a wiring diagram that any competent electrician can understand. What they haven't done is supply a wiring diagram for wiring to your switch.

However given that Myfords never supplied a switch as standard, they did supply two as extras and supported these in their handbook iI feel that it's asking too much for them to offer advise that could damage a motor if incorrectly applied and the customer would expect them to be responsible for this.

 

From your original post where you described the wiring one live for forward and one for reverse is not how the standard Dewhurst switches were wired so chances are someone in the past history of this machine has crowbared any old switch onto this machine.

 

Sorry but I feel they have done all that could be expected of them, the ball is in your court getting this motor to fit a non standard installation.

.

Edited By John Stevenson on 04/05/2014 13:19:15

[Glen Morgan 1Participant @glenmorgan1]

Nick,

Near Midhurst, West Sussex.

[Les Jones 1Participant @lesjones1]

I agree John, The information provided is enough for someone with electrical knowledge to be able to get it to work. This is a bit like the OP on the "Inverter remote stop" thread complaining about the manual on the inverter. I thought it was an excellent manual which gave all the information required to use in in many different configurations.

Les.

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