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  1. #11
    Quote Originally Posted by Clive S View Post
    Fine Lee I was not taking the p#'@s I just thought that the Voltage had to be added etc for the sake of people with no knowledge of sparky stuff.
    I know mate :), I was only having fun, my ask of "how i did" was actually sincere as I only know what I've learnt in an unformal way, im no professional.

    At the same time I thought it was a good cue for providing the knowledge, as like you say those conversions need to take the operating voltage into consideration if starting from the beginning and doing your own calculations.

    .Me
    .Me

  2. #12
    Quote Originally Posted by Clive S View Post
    I still think 0.75mm is fine the motor is 1.5Kw 3 phase and quite short. There are many people using that on this forum.
    Yes, I know many people use that, but 0.75mm2 is lamp wire, not for motors, at least not for motors of the sizes we are discussing. Yes, handling a 1.5mm2 is not as easy as 0.75mm2, but still, not that difficult if you know how to solder and connect. Also, when you crimp the VFD end (which I guess you do) it is considerably safer to use 1.5mm2 than the lamp wire. 0.75mm2 or 0.5mm2 is for control wires in this area, not power.

    Then again, this is just my opinion. I know many people will disagree and many people use far too thin cables for convenience, price and for lack of better knowledge and that "it works", also because they read these forums and go for the "majority rule" principle.
    Last edited by A_Camera; 26-05-2016 at 01:02 PM.

  3. #13
    Ok it is not lamp wire it is CY cable the smaller size is easier to connect into some of the small plugs and cable trays.
    I see the chart you put up that is for domestic wiring and I agree with that.

    The 1.5Kw is spread over the three cables as well.

    But it is your opinion but not mine. I do use 1.5mm generally.
    ..Clive
    The more you know, The better you know, How little you know

  4. #14
    Quote Originally Posted by Clive S View Post
    Ok it is not lamp wire it is CY cable the smaller size is easier to connect into some of the small plugs and cable trays.
    I see the chart you put up that is for domestic wiring and I agree with that.

    The 1.5Kw is spread over the three cables as well.

    But it is your opinion but not mine. I do use 1.5mm generally.
    I call it lamp wire because the conductor is as thin as it is for lamps. The fact that it is shielded is a different matter. I chose 1.5mm2 for the power and 0.75mm2 for the control and low voltage wires. Admittedly, it was not that easy to fit the 1.5mm2 into the plug, but it is just a one time work, so once it is done in one end, everything is much better and easier. Crimping is simple and no bother at all. If the wires are too thin crimping cables shoes becomes insecure and problematic.

  5. #15
    Quote Originally Posted by A_Camera View Post
    It is thinner and lighter but it should be 1.5mm2. 0.75mm is OK for control signals but actually too thin for the power.
    6A for Control Signals.!!!!!. .

    Don't worry Bee it will be fine. These spindles at full load only pull 8A. In practise and while heavy cutting they actually rarely pull above 5A. 0.75mm2 is rated 6A and this is very conservative rating. Again in practice and for the very rare occassions you do pull full load of spindle/VFD it will easily allow to pull 8-10A without any trouble. In case of Short Circuit the VFD it's self will protect you with it's Max current setting and then you have the Fuse.

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  7. #16
    Quote Originally Posted by JAZZCNC View Post
    6A for Control Signals.!!!!!. .

    Don't worry Bee it will be fine. These spindles at full load only pull 8A. In practise and while heavy cutting they actually rarely pull above 5A. 0.75mm2 is rated 6A and this is very conservative rating. Again in practice and for the very rare occassions you do pull full load of spindle/VFD it will easily allow to pull 8-10A without any trouble. In case of Short Circuit the VFD it's self will protect you with it's Max current setting and then you have the Fuse.
    Common sense at last
    ..Clive
    The more you know, The better you know, How little you know

  8. #17
    Quote Originally Posted by Clive S View Post
    Common sense at last
    Suppose Makes a change from talking bollocks.

  9. #18
    Quote Originally Posted by A_Camera View Post
    I call it lamp wire because the conductor is as thin as it is for lamps. The fact that it is shielded is a different matter. I chose 1.5mm2 for the power and 0.75mm2 for the control and low voltage wires. Admittedly, it was not that easy to fit the 1.5mm2 into the plug, but it is just a one time work, so once it is done in one end, everything is much better and easier. Crimping is simple and no bother at all. If the wires are too thin crimping cables shoes becomes insecure and problematic.
    Do you have a hair dryer at hand? Check the cable and power. Mine has 1700W and a 2x0.75mm2 cable. And is german made.


    Now regarding the question in this thread, I would never use a 0.75mm2 "normal" stranded cable in a CNC machine. Since all the cross-sections are composed of thin wires with the same diameter, a larger cable will last longer. If/when half the wires of the 0.75mm2 conductor (only 10-12 of them) will be broken, probably the rest will blow. For a 1.5mm2 cable, three times the number of wires needs to be broken to come to the same situation.

    Using special flexible fine stranded cables, even 3x0.5mm2 will be enough for a 3 phase 1.5kw spindle on a short distance

    Here I attach some more charts...
    Attached Thumbnails Attached Thumbnails Igus.pdf  

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  11. #19
    Quote Originally Posted by JAZZCNC View Post
    6A for Control Signals.!!!!!. .

    Don't worry Bee it will be fine. These spindles at full load only pull 8A. In practise and while heavy cutting they actually rarely pull above 5A. 0.75mm2 is rated 6A and this is very conservative rating. Again in practice and for the very rare occassions you do pull full load of spindle/VFD it will easily allow to pull 8-10A without any trouble. In case of Short Circuit the VFD it's self will protect you with it's Max current setting and then you have the Fuse.
    You can't ONLY go only after currents, if that was all that mattered we could use hair thin wires for all type of communications. You are blindly staring at one parameter only.

    Generally speaking, yes, 0.75mm2 is enough for most cases for the spindle, but why use something as thin as that if 1.5mm2 is safer, stronger, not much heavier, better suited for the purpose and hardly much more expensive. Can you come up with ONE good reason other than most people don't continually use up more than 5A?

    I chose 0,75mm2 for the control signals because that is what I have, apart from 1.5mm2 and FTP CAT6 cables (0.5mm2), so I chose the 0.75mm2. The FTP cable would be good as well, but I like the Ölflex cable more, it is easier to handle for the purpose.

  12. #20
    Quote Originally Posted by Clive S View Post
    Common sense at last

    Whatever rocks your boat...

    To me, the common sense is NOT to use such thin wires for this purpose. It works, but it is AGAINST common sense.

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