# Choosing right cable size for high current application

Just to give more detail:

This is for LV System upgrade for front end electronic(FEE) cards for detector application. Currently the LV system uses Wiener Pl512 LVPS (low voltage power supplies) rated at 25A 250W 8V max to supply the front end electronics with 2.5V via 30m of 16mm^2 to a filter box then from there 3m of 2.5mm^2 to the FEE cards using sense wire connected as well which has been running fine for years.

Now the new FEE cards require input voltage at 1.7V which means power consumption increases and the LVPS at 25A cannot support the consumption of the FEEs.

My idea is to use DCDC at the filter box side that will support the increased current requirement of 50A for FEE cards at 5V taking into voltdrop across cable (1.7V+3.3V - is this correct for 2.5mm^2 cable of length 3m with copper linear resistivity Rho = 17. 10-9 Ohm.m?) and will not source more than the 25A from the current LVPS.

I am still getting a hang of power electronics as i am from software background. So I just wanted to know whats the best way to go about deciding or calculating whether the cables that already exist of 2.5mm^2 for 3m are sufficient to handle the new requirements. We talking about 100+ cables and going thicker cabling route might mean a lot of rework and extra costing due to spacing constraints. Is there any ideas about this? Would using a cooling system help?

• Shove it through one of the thousands of ampacity calculators on the Web. – Ignacio Vazquez-Abrams Oct 10 '17 at 9:48
• 1.7V, 50A.. 3 meters of 2.5mmˆ2.. Have you calculated the voltage drop yet? (Unless you have sense wires..) – Wesley Lee Oct 10 '17 at 9:49
• Huh? What's a "2.5mm2" cable? It's not a typo since you wrote it twice. Also, we use English here. Your post is borderline comprehensible. Closing as unclear. – Olin Lathrop Oct 10 '17 at 10:47
• I think the language is perfectly cromulent, but I still think it's rather unclear what you actually want to do. 50 ampere at 1.7 volt over a 3 metre long cable doesn't sound like a very good design. – pipe Oct 10 '17 at 11:08