12V DC power supply - 2 maximum cable meters?

[Patatrace]

Hello,

I want to install 18 LED spots (15x 3w + 3x 5w) in a room whose farthest one needs 10 meters of cables. Everything will be powered by Electronic Power Supply 230V - 12V CC 100W.

Reading 15 100 1,5 standard I find that 30mm² cable will do the trick knowing that I distribute the load on the two rails of the power supply (ie about 60w rail so XNUMXw in all).

However, I came across a so-called UTE C 15-559 standard, the documentation of which is not free (a shame!) But an extract of which tells me "electronic converters operate at frequencies of 35 to 40Khz which is why the cable length in secondary school must never exceed 2 meters "

Can someone help me decipher this please?

[Christophe]

Uh, I would have a hard time helping you because I do not understand it (we're here to learn huh) ... what's this kHz story in a DC power supply?

The standard concerns may be the CA-CA pseudo sinus transformer of this type https://www.econologie.com/shop/transfor ... p-311.html but I do not see where the 40 kHz would come from? I have already measured one with an oscilloscope: the signal is not "clean" but its frequency is 50 Hz ...

So this standard = ???? (if it concerned the LV lighting, no stretched wire lighting of more than 2m would be approved ...)

In your case there is no problem: you need 5 A, 1.5 mm² is largely sufficient for 10m. If you have a doubt, measure the voltage at the furthest point and compare it to that at the output of the power supply.

You will surely have other more detailed opinions!

[Forhorse]

In my opinion there is a big amalgam of a lot of things there ...

[dedeleco]

electronic converters operate at frequencies of 35 to 40Khz, which is why the lengths of the cable at the secondary must never exceed 2 meters "

technically there may be converters at these frequencies and long cables may leave residual voltage after the output filtering that could be troublesome on other devices sensitive to these parasites that pass between son parasitic capacitance and induction. ???
The best is to try, because the standards are strong to avoid problems sometimes very rare, especially for electromagnetic interference.
The chokes of the long leads can disturb the converter, if lack of luck unlikely.
An oscilloscope can detect.

[Christophe]

Yes really strange this case.
With 2m cable we do almost nothing.

Anyway the length depends on the section and the times of the armor ... so say 2m like that ????

[Remundo]

if you do not want to break your head, expect 5A / mm² of copper.

100 W in 12V make 8A

So 1,5 mm² are suitable. But 2,5 mm² will be better.

But it's still a shame to raise the amperage for nothing ... This leads to "put copper"

You did not find any fixtures to your taste in 220V?

[Gaston]

The standard concerns may be the CA-CA pseudo sinus transformer of this type https://www.econologie.com/shop/transfor ... p-311.html but I do not see where the 40 kHz would come from? I have already measured one with an oscilloscope: the signal is not "clean" but its frequency is 50 Hz ...

I also think that it is these "transformers" who are targeted.

The base frequency is indeed 50Hz, but there are harmonics at the chopping frequency (20 to 40 kHz effectively) which are responsible for what you see on the oscilloscope as "unclean".
At this frequency, an unshielded cable of several meters can make a good emission antenna ...

For a DC power supply, no problem, I think.

[Forhorse]

5A / mm² is an empirical method for very short distance. the good old method of the pifometer with a little math in what.
For low voltage, as soon as the distance exceeds a few meters, calculations are a little more complicated than that!
Or hello surprise at the end of the line.

[Christophe]

That is Forhorse? What is the method in 12V CC or CA?

[dedeleco]

We calculate the resistance of the wires and the corresponding voltage loss which believes in their length !!