1. What is meant by sq mm. in a copper wiring system?
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The size & current carrying capacity of the copper, aluminum, or any cables are referred to or recognized in sq. mm.
But, what does that mean?
sq. mm. refers to the sectional area of an individual strand, multiplied by the no. of strands present in a single wire.
In the case of solid wires, the sectional area of a single wire present in the cable is denoted in sq. mm.
We will understand it clearly when we go through the calculation procedure as given below.
2. How to calculate the copper wire size?
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As you can observe in the above drawing, a copper wire is cut by section -AA & the sectional diameter of the wire (strand) is d.
The sectional area of the wire is calculated by the formula = [πd² ➗ 4]
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In solid cables, the sq. mm. of the cable is calculated by the formula
= Sectional area of the wire
= [πd² ➗ 4]
In the case of stranded wires, the sq. mm. of the cable is calculated by the formula
= [ no. of strands 🇽 sectional area of the individual strand.]
= [ n 🇽 (πd² ➗ 4)]
Example:
Let us consider the diameter of a single strand of the above cable as 0.674mm. The no. of strands present in the cable is 7.
Now,
The size of the cable
= [n 🇽 (πd² ➗ 4)]
= [7 🇽 (π 🇽 0.674² ➗ 4)]
= [ 7🇽 (1.427 ➗ 4)]
= [ 7 🇽 0.357]
= 2.499 sq. mm.
By rounding off, the size of the cable = 2.50 sq. mm.
Note:
If you want to calculate the sq mm. of a particular cable by yourself, you have to use a vernier caliper to find the diameter (d) of a strand.
To go through the articles on Estimation & calculation in civil engineering, click here.
Thank you for going through these calculation steps❤. Have a good day 😄.
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