Which thickness CY cable do I need for 1.5kW spindle?

[Clive S]

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.

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.

[A_Camera]

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.

[Clive S]

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.

[A_Camera]

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.

[paulus.v]

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...

[A_Camera]

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.

Fine. Now, run that hair dryer for 8 hours non-stop and see what happens...

Hair dryers are NOT high frequency controlled equipment, they have a tiny motor and they are not designed to be run for more than a few minutes a time so you can't really take that as a good example. My drilling machines have 1.5mm2 cables, they are also German made, and none of them are over 1kW. Why? Because they are designed for sudden current rushes and for long usage time.

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.

That is yet another good argument for a stronger cable. On the other hand, if you handle the cable as you supposed to handle and don't bend it more than it is specified for *AND* use the cable type which is designed for the application (i.e. flexible cable chain use) than you should not have any broken wires during the life time of your machine. Remember that I am talking about quality cables, not the one used in the hair dryer.

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

Yes, of course. I have never claimed otherwise. Just that I can't really see any *GOOD* reason for not using something stronger than 0.75mm2. Never the less, there is a group of people who prefer the easiest approach, which is using the thinnest possible cables. Beats me why, I don't understand that philosophy and prefer to have margins if I can. On the other hand... so far I have not had any electrical issues, and I don't expect to have any later on.

[Clive S]

Yes, of course. I have never claimed otherwise

I thought you claimed it here:-

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

Well you appear to have jumped on the op's post nearly 3 months after he last posted and muddied the waters quite well.

I think you need to take a good look at your own machine before nit picking others.
I will not be posting any more on this subject. So please lets not take any more space on his post.

By all means start one of your own.