Help needed with lathe electrical’s!!

  1. farmer_joe Member

    Messages:
    47
    Location:
    Tonbridge, Great Britain
    Anyone on here any good with industrial/3phase/machine electrics?

    Bought a new to me Smart and Brown 1024, which is in very nice condition. It has arrived and yesterday went through the ordeal of taking workshop roof off to take old lathe out and put new in.

    When disconnected it had been hard wired and it was just cut off wired on a plug and hooked up to phase converter. It also has a lead that needs to be plugged into a 110v transformer, which I have done. this iS obviously not original and on further inspection it seems that there used to be a small 415v to 110v 100va transformer in the lathes electrical box. It’s no longer there so I’m guessing it shat the bed, hence the need for an external transformer. I’ll sort a proper replacement at some point.

    AnyWay, when I tried and fire up the lathe there is a hideous buzzing noise and vibration that literally shakes my meagre workshop. I have not a clue what the issue is! It does this in forward or reverse. The spindle turns slowly, not as it should.

    Ive tried all the possible wire configurations in the plug, I tested the 110 transformer to make sure it works which it does.

    Anyone have any ideas? Or anyone localish to the Tonbridge/Tunbridge Wells are that knows about these things that would look at it? Paid for of course. I don’t want to mess up the lathe and playing around with 415v scares the Sh!t out of me!

    many thanks,
    Joe.
     
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  2. Brad93

    Brad93 M J B Engineering

    Messages:
    10,398
    Location:
    Essex
    You’ve got a phase issue.

    110v will be for the control circuit or low voltage lighting.
     
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  3. Memmeddu

    Memmeddu Member

    Messages:
    2,954
    Location:
    Italia Sardegna
    I believe that shall be possible that this issue could be caused by a sort of brake that still engaged .
    But I think that would be useful to know

    Some pictures
    And try to search or draw the wiring diagram of it
    I did already work on electricals on industrial equipment and they usually have safeties brakes and all other stuff.
     
  4. farmer_joe Member

    Messages:
    47
    Location:
    Tonbridge, Great Britain
    Hi Brad,

    it did originally have a low voltage light but this is long gone. I think the 110 is for the speed control, but not 100% on this. If it’s a phase issue where do I need to start looking? I know the phase converter works as it should ad it’s been running a 5hp mill for the last year or so.
    The converter is a rotary that’s switchable between 7.5hp and 15hp, so more than up to the job.

    Memmeddu,
    I’d does have a brake I believe, it operates automatically so could well be the issue.

    upload_2020-9-20_16-31-7.png
    upload_2020-9-20_16-31-34.jpeg
    here’s an an appropriate wiring diagram, which I don’t fully understand. The little I learnt at school is long forgotten. The second pic is of the electrical cabinet, not mine though. Mine is missing the transformer at the bottom right, this is replaced externally via a site type transformer.
     
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  5. daedalusminos Member

    Messages:
    1,076
    Location:
    Norwich
    Is your phase converter a true three phase rotary one or is it a static converter?
     
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  6. farmer_joe Member

    Messages:
    47
    Location:
    Tonbridge, Great Britain
    It’s a 15hp rotary phase converter.
     
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  7. farmer_joe Member

    Messages:
    47
    Location:
    Tonbridge, Great Britain
    1 thing that springs to mind is that the original 110v transformer is 100va and the the site box is 3.3kva. Would this make a difference?

    I’ll try and find out what the previous user had.
     
  8. brightspark

    brightspark Member

    Messages:
    31,752
    Location:
    yarm stockton on tees
    presumably your phase converter has a neutral as well as the 3 phases . you would need to test the output of the 3 phases to make sure your getting full voltage on each phase to the machine
     
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  9. farmer_joe Member

    Messages:
    47
    Location:
    Tonbridge, Great Britain
    It does Brightspark, when I last checked it was giving out full voltage. I’ll head out and double check that it is still doing so.

    It does fire up the mill just fine still.
     
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  10. brightspark

    brightspark Member

    Messages:
    31,752
    Location:
    yarm stockton on tees
    just a thought are the mains fuses all ok :)one never knows
     
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  11. hermetic

    hermetic Member

    Messages:
    187
    Yorkshire UK
    watch the relays/contactors when you start the machine, if the noise is coming from the contactors chattering it may be that the phase convertor output will not operate the coils properly. You need to make sure that the phase which is used for the coils in the contactors is connected to the "real" single phase output from the convertor, and not one of the generated legs coming out of the phase convertor. Rotary phase convertors are better than static ones, but they are not perfect by any means. Try changing the phases round to see if it makes a difference if you cannot trace which phase the coils are fed by, you may need to change them twice to try all combinations! I assume it was running on normal "real" three phase at its former home?

    Phil
     
  12. farmer_joe Member

    Messages:
    47
    Location:
    Tonbridge, Great Britain
    Checked Voltages. 416 to 453.
    The converter was built by an old electrical engineer. When I got it it was in bits but he explained how it went back together. I rebuilt it as instructed and it’s worked fine with the mill.
     
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  13. carbon

    carbon Member

    Messages:
    1,690
    Location:
    S. Glos. U.K
    From the included diagram above it looks like the control voltage is 240v as neutral and one live is used. The contractors should have the coil voltage marked on them but may be difficult to see. The 110v looks like it’s just for the light
     
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  14. brightspark

    brightspark Member

    Messages:
    31,752
    Location:
    yarm stockton on tees
    does the main motor contactor pull in fully when you turn it on. give it a push with a screwdriver by hand and see if motor fires up
     
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  15. farmer_joe Member

    Messages:
    47
    Location:
    Tonbridge, Great Britain
    Mains fuses just fine! Always worth checking!

    at its last home it was run from a rotary phase converter. The seller isn’t a great deal of help as it was his fathers and he’s passed away.

    I’ve just been and tried all the possible wire combinations in the plug if that makes sense, is that what you mean by trying to find the correct phase? If so it didn’t make a difference! Still same horrible buzzing.

    Any other ideas?
     
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  16. mtt.tr

    mtt.tr Member

    Messages:
    4,095
    Essex England
    Will the chuck turn its not a stalled motor?
     
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  17. brightspark

    brightspark Member

    Messages:
    31,752
    Location:
    yarm stockton on tees
    check the voltage at the motor there should be 415 at least over the 3 phases put the leads on the cables in any order l1 to live 3 then one to live 2 then 2 to live 3
     
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  18. farmer_joe Member

    Messages:
    47
    Location:
    Tonbridge, Great Britain
    The main contactor pulls, I helped it right in with a screwdriver. When pushed right in with the screwdriver it makes the horrible noise but the spindle doesn’t try and turn. The spindle does turn when I push the start button on the lathe, thought not very fast. Problem I have is my workshop is very small and the lathe is pretty much tight up against the wall leaving me unable to access the motor panel. I’ll have to try and lever it out to get at it.
     
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  19. brightspark

    brightspark Member

    Messages:
    31,752
    Location:
    yarm stockton on tees
    its preferable to access the main motor leads after the contactors or as close ass and work your way back
     
  20. farmer_joe Member

    Messages:
    47
    Location:
    Tonbridge, Great Britain
    Carbon,

    if the 110 isn’t turned on then nothing happens when I try and start the lathe. So it’s obviously needed. Unless my wiring diagram is wrong! I have found A second and they’re Slightly different. It may be that the one I put up earlier might not be correct. What do we think of this one.

    upload_2020-9-20_18-10-34.png
    It’s a 4 pin plug not 5.
     
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