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need help to calculate max current capacity

3K views 21 replies 8 participants last post by  LJSMITH1 
#1 ·
Hi colleaques,

I need to know how much maximum current should flow in this conductor (copper bar).

bar = 15 mmsq
hole = 9 mmsq
(picture attached)

Thanks
 

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#6 ·
Aldrin, will it be connected to the feet or the testicles of your intended victim? This makes a difference you know, since skin resistance will vary the current flow as well as the rather expensive piece of metal in your picture.
 
#18 ·
You see that (1) beside the copper conductor? If the metal used in your terminal strip is a different kind of metal, then the chart cannot be compared. If the manufacturer has it rated at 70 amps, then I would run it at 70 amps. I've never seen a terminal strip burn it two. It's usually the connections that burn up from not torquing them.
 
#21 ·
I have news on this, I just got back from a call. There where very similar 70 amp rated Allen Bradley terminal blocks on site and they where running anything from 50 to 100 amps DC through them with no problem.
 
#22 · (Edited)
Something I found:

I=(7.7 *(A^(0.5))*(P^(0.39))))

for an ambient temp of 40-50c
where:
A - Cross sectional area of conductor in sq.mm
P - Perimeter of conductor in mm.
Will work for AC or DC current.


Or try using ohms law after you find the specific resistance of the material you are working with:

R = ρ(l/A)

Where,
R = Resistance, measured along the conductor's length
ρ = Specific resistance of the substance
l = Length of the conductor
A = Cross-sectional area of the conductor
Follow-up question: algebraically manipulate this equation to solve for length (l) instead of solving for resistance (R) as shown

Metal type - ρ in Ω · cmil / ft @ 32oF - ρ in Ω · cmil / ft @ 75oF
Zinc (very pure) 34.595 37.957
Tin (pure) 78.489 86.748
Copper (pure annealed) 9.390 10.351
Copper (hard-drawn) 9.810 10.745
Copper (annealed) 9.590 10.505
Platinum (pure) 65.670 71.418
Silver (pure annealed) 8.831 9.674
Nickel 74.128 85.138
Steel (wire) 81.179 90.150
Iron (approx. pure) 54.529 62.643
Gold (99.9 % pure) 13.216 14.404
Aluminum (99.5 % pure) 15.219 16.758

Make sure you properly calculate the area of the smallest solid portion of the bar around the hole....
 
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