Myford ML7 motor wiring

Help please!

I have a Myford lathe and it needs a new motor. I have an EMG elettromeccanica one that fits physically (it was supplied as a replacement for the original) My problem is the terminal markings (lathe is fitted with a Dewhurst reversing switch)

What do I connect to where?

Motor terminals are:

U1(blue wire from motor) currently linked to W2 (red wire from motor)

V1 (red wire from motor) currently linked to U2 (one side of capacitor connected)

W1 (nothing connected)

V2 (brown wire from motor and other side of capacitor)

Drum switch is connected to the eight terminal block as per drum switch instructions.

Many thanks

Steve

Is the Dewhurst set up for 3 phase or single phase ? Adam

Sorry, I should have said single phase.

Hi Steve,
Is the information you have given referring to the old motor and wire colours the wires that come from the switch, (Or are they the wires from inside the motor to the terminals.) ?

Les.

Hi Les,

The info refers to the new motor (unfortunately the old one was removed before I got it) and the wires are those that disappear into the depths of the motor.

At present there is no wiring between the terminal block and the motor.

Thanks Steve

Sorry, rereading your post I can see that you have a single phase setup. Well U1 and U2 are normally Run terminals but you need to establish if this is the usual capacitor start, induction run motor or capacitor start capacitor run motor, Assuming it is the former, one circuit is the U1-U2 run circuit and the other circuit is the Capacitor, start, centrifugal switch circuit. The Dewhurst taps into the U1 and U2 circuit , taking the flow into the Capacitor, start, centrifugal switch and reversing the direction around the cap,start,centrifugal sw circuit according to whether switched to Fwd or Rev. Bearing this i mind, you should be able to work out what goes where without relying on the existing colour coding which may be erroneous. Tubal Cain covers most motors wiring in his book although I do not have it to hand. Does the new EMG have resilient rubber mounts - shame if it does not.

Hi Adam,

Does that mean I have to remove the physical links between U1-W2 and V1-U2?

Does it also mean that I only have a connection between two cores (to U1 and U2- three counting earth) from the motor to the Dewhurst?

No resilient mounts unfortunately!

apologies if these questions seem obvious.

Steve

Hi Steve,
You will need a four core (+earth) cable between the motor and the switch. You will need to remove both links. I am making no assumptions on the colour coding of the wires inside the motor. I believe that the run winding is between V1 and W2 and the start winding between U1 and V2. Confirm this is the case by measuring the resistance between V1 and W2 I would expect it to be a few ohms (Probably less than 10) Measure the resistance between U1 and V2 I would expect this to be between 10 and 20 ohms. Confirm that you get an infinite reading between V1 and V2 IF THIS IS THE CASE then the pair from the switch that does not reverse polarity goes to V1 and W2 The pair that reverse polarity between forward and reverse go to U1 and U2. If you cannot identify the two pairs from the switch we will need to ask more questions to identify them.

Les.

Sorry Steve, but since your U2 is connected to the capacitor circuit it would seem that the U1-U2 circuit is not the Run circuit as I thought. You will have to research italian wiring diagrams online. Without trying to irritate you, I would suggest selling it on ebay and buying a used resilient mount British motor (Brook Crompton or Hoover) for it on ebay which will give less vibration and easier for spares if ever needed.

Rather than remortgaging for a Brook Crompton, he Manufacturer's website has this pdf which shows the connections with English instructions:

http://www.emgelettromeccanica.it/data/public/file/9_schemi_collegamento.pdf

Neil

Edited By Neil Wyatt on 10/09/2014 08:44:29

Well spotted Neil, (I looked on their website but could not find that information.) I seems to confirm my theory as to how the motor is wired. There seems to be an error on the connections for anticlockwise rotation. The right hand end of the capacitor is not connected to anything. It should go to V2 (One end of the start winding ) as in the drawing for clockwise rotation.

Les.

Hi Guys

I have a similar problem.

I can't get the Stanton switch to switch forward/reverse from the Brooke Crompton motor.

On my Super 7

The switch has different connections to that shown in the manual.

LH from the top, rear view

C B 1

RH

3 2 A

I have drawings on PDF but can't attach them.

Without them the above wont mean a lot.

How do I attach them?

Thanks

Ian

Hi Ian,
As far as I know this forum does not support .PFD files to be inserted into forum posts. You could convert it to a .JPG file by using a screen capture program such as "Gadwin print screen" You could also look for a utility program to do the conversion. You could also use "Dropbox" by putting the .PDF file in your public folder. Then put the URL of the public link to the file as a link in your forum post. If you only need to send it to one person then get them to send you a PM with their email address (To avoid putting email addresses on the forum.) then send it as an attachment to a normal email.

Les.

Hi Les,

Thanks for the info.

I have converted them to .JPG but still can't load them.

I will try Dropbox when I get home tonight.

Ian

Hi Ian,
To add pictures to a post the files have to be first uploaded to your albums. To do this click on albums on the green band near the top of the forum web page. When you have the files there you can add them to a post by clicking on the camera icon at the top of the box where you are typing the message. By the way Thanks for bringing this thread back to life since the OP seems to have lost interest in having his problem fixed.

Les.

Edited By Les Jones 1 on 23/09/2014 11:46:01

Hi Les.

As you can see the photos are on the forum,

thanks to a friend who came into the office.

Ian.

Hi Ian,
Can you confirm if the switch is 2 positions (Forward Reverse) or 3 positions (Forward off reverse) ? Also can you confirm that the table labelled "connections" in the picture of switch information shows the contacts that connect together in the 2 or 3 positions of the switch and in no position terminal 3 connects to any of the other terminals ? If this is the case then this switch cannot reverse the motor. Is this data from a document or have you worked it out by testing for continuity between the terminals ?

Les.

Hi Les,

The switch is 3 position.

It is probably the original switch the lathe is on a Myford industrial stand.

The switch position is something I worked out.

I'll check position 3 tonight.

Ian

Hi Les,

Thanks for all your help.

3 is connected to C when the switch is in reverse.

Ian.