I need to power industrial computer with 50m cable. What to use, 220 or 12v?

[Terminator3]

Hello all! I need to power small computer (12v 4a), which is 50 meters away from nearest 220v power box. What would be better solution, put 50 meters rvv3 0.5mm with 300v/500v isolation, and then 220to12v power supply near computer, or 50 meters 12v cable? some rvv2. It seems 220v would be best solution (interference, efficiency). If use 12v cable , need to put some filtering before PC, and cannot use additional 220v fan..

 

[FvM]

You can answer the question yourself by calculating the required cross section for a 12 V cable. I end up with more than 10 mm² for 5 % voltage drop.

 

[Terminator3]

i see. How about rvv3 x 0.5mm^2 (300/300v isolation) at 220v 0.3A?

 

[FvM]

The 220V cable voltage drop is quite small, even if the power supply isn't PF-corrected and has a higher input current, let's say 1 A.

There's howver a special point that should be observed. Due to the high cable resistance (about 3.5 ohms loop resistance), the switch board fuse will only slowly trip in case of a short circuit. If it's a ground fault, the case of the remote computer exposes e.g. 110V before the fuse trips. A low rated fuse or even better a RCD should be used to protect the circuit.