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Domestic single phase to 3 phase advice please

Discussion in 'Electrics UK' started by BotleyBouy, 27 Nov 2019.

  1. BotleyBouy

    BotleyBouy

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    I'm buying an industrial sewing machine fitted with an Efka 3-phase motor. Here is a photo of
    the data plate so you can see what I've got...
    IMG_20191119_162729.jpg
    And this is the motor as fitted to the machine...
    IMG_20191122_145352.jpg
    Can someone please advise which is the best way to go. The main criteria I have are (i) low speed control & (ii) torque. The machine needs to be able to push the needle through several layers of thick material at slow speed and under control, eg one stitch at a time. As I see it I have these options:-
    1. Buy a new 240V 550W servo motor like this https://www.tysew.co.uk/industrial-...achine-energy-saving-servo-motor?search=motor at around £150. A few alterations needed to fit and not much information on available torque. It's hard to see how such a tiddly motor could deliver the same torque as the existing unit.
    2. Buy an inverter. This option means no change to the motor, brackets, drive belt, control pedal etc but here I'm completely confused by the choice available. As I understand it, I need an inverter to change my 240V domestic to 415V 3-phase but the more I read the more confused I get. Is there a simple way of finding the correct unit at a sensible price? Will there be any loss of low speed control or torque buy using an inverter?
    3. Have the existing motor re-wound to 240V AC. The advantages in keeping the existing equipment as per (2) but will there be any loss of low speed control or torque?
    This is the sewing machine in question...
    IMG_20191122_145328.jpg
    Are there any other options?
    Many thanks in advance for all help and advice offered.
     
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  3. flameport

    flameport

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    Option 2 - an inverter. More likely to be available as a VFD, variable frequency drive, although in this case you don't need the variable part, it would just be set it to 50Hz output.
    Rating at least that of the motor (550W) and preferably a bit more, such as 750W.
    Two choices - known brand items for a few £100s, or a Chinese import which can be had for ~£50.
    In both cases it will need to be configured correctly before using.

    Replacing the motor would require detailed info on the specifications, not just the power.
    Rewinding the existing motor has the same problem and will cost far more than a new motor.
     
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  4. ericmark

    ericmark

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    The inverter does not need to step up voltage, you change motor to delta instead of star, but been a long time since I have fitted inverters so don't know what is available now.
     
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  5. Notch7

    Notch7

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    It looks like the motor can work as 240v 3phase so a vfd will be suitable.

    You could try posting on ukworkshop forum, its a question that comes up often and there are guys on there that can advise.

    https://www.ukworkshop.co.uk/forums/
     
  6. bernardgreen

    bernardgreen

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  7. SUNRAY

    SUNRAY

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    This may seem stupid but have you confirmed that this machine does require a 3ph supply?
    It's been 40 years since I had involvement with a sewing machine shop and I'm fairly certain we worked on variostops in their workshop with only a single phase supply.
    Can you check the variostop rating plate?
     
  8. BotleyBouy

    BotleyBouy

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    This is the data plate..
    IMG_20191119_162729.jpg
     
  9. BotleyBouy

    BotleyBouy

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    If an inverter is the preferred route then how do I choose from the bewildering choice (to me anyway) available? For example, this is available from RS https://uk.rs-online.com/web/p/inverter-drives/1223411 ; this one is roughly half the price off ebay https://www.ebay.co.uk/itm/5A-Singl...262689&hash=item3fb501a2fa:g:vI4AAOSwqnlcG-mM; this one is also on ebay https://www.ebay.co.uk/itm/Schneide...421821?hash=item5b63aec43d:g:eI4AAOSwhe9dvbIb seems like a quality product, on the face of it anyway. Lots of choice, but how to choose?

    Would any of these adversely affect the power, torque or controllability of the motor?
     
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  11. bernardgreen

    bernardgreen

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    It is an induction motor with an electromagnetic clutch.
    upload_2019-11-28_11-57-48.png
     
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  12. ericmark

    ericmark

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    Even when I was still working with drives every day, selecting a drive and motor was hard, I remember swapping whole motor for one with the drive built in to get the control required. It really is a case of close eyes and stick in a pin.
     
  13. Simon35

    Simon35

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    A
    An inverter for direct connection to a motor does not produce a pure sine wave output, so whatever is controlling the motor speed and torque currently would need to cope with that.

    If you are thinking about directly controlling this existing motor with a new inverter, make sure the insulation class of the motor windings is adequate for the voltage stresses a new inverter will impose, caused by the rapid switching of the drive outputs.

    Bernard reckons the motor has an electromagnetic brake. Is that a separate supply? Or is it taken from the motor winding connections?
     
    Last edited: 28 Nov 2019
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  14. Simon35

    Simon35

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    It really isn't a case of closing your eyes and stick in a pin.

    What mechanical power do I need, over what range of speed.

    How tight do I need my speed/torque/position control to be.

    What signals are controlling the drive.

    It's called engineering.
     
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  15. ericmark

    ericmark

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    The inverter I bought was fitted in the control panel, and the spec said it should do the job, but we had EMC problems with the inverter affecting the ASii control bus so it had to me moved and this involved a lot of rewiring.

    In another case the inverter should according to spec work the motor, but it was found the timing from ASii and inverter were not accurate enough to either remove drive before brake applied or allow it to over shoot, a motor with the ASii, brake, gearbox and motor all combined in one unit was the answer, but it was in real terms a case where the spec for drive was just slightly out, the way forward was to gain experience, and to with some trial and error find out what units worked together well.

    I would not think the sewing machine uses items with would cause EMC problems, or timing problems, but only one way to find out, and that is to try it. In the main motor drives must not be disconnected from the motor, when some one fitted a drive, reversing contactor then motor it wrecked the drive. The reversing has to be done in the drive, how one can do it with a sewing machine I am not sure, but likely more involved than simply adding a drive.
     
  16. SUNRAY

    SUNRAY

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    This is the one I was hoping for
    upload_2019-11-28_14-41-57.png
    There are many format variations on industrial sewing machines (and other machines for that matter) and some used a 3ph motor with a single phase VFD.
     
  17. crystal ball

    crystal ball

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    It has look of a former Clarks shoes machine with the bits of earth cable lying about, the clutch was supplied from the windings AFAIK, as was the work light,
     
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