electrical wire sizing!!!


Postby johnnyuhtar » Sun Oct 14, 2007 7:58 pm

Hi hope someone can clear this up How Is multi strand wire measured???
eg, 16mm2 It has 7 strands each measuring 1.7mm thick when added together only add up to 11.9mm which is NOT 16mm2 !!!
A friend told me this theroy using pi :- 3.142 x1.7 x1.7 =9.08038 /4= 2.27095 x7=15.89665 which he says is where the 16mm comes from !!! Is this correct anyone please help Ive been on trying to work it out now for 4 days thanks jonnny
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Postby RowanMook » Mon Oct 15, 2007 10:58 am

You are trying to calculate the cross sectional area, this is the formula Pi times the radius squared.

That gives you 1.7/2 radius= 0.85
Pi= 3.14159265

=0.85*0.85*3.1415926 = 2.2698

Times 7 strands 2.2698*7=15.8886mm Squared

This is subject to the accuracy of the micrometer measurement of the strand.
Remember this is cross sectional area, not the width of the strands.
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Postby RowanMook » Mon Oct 15, 2007 4:43 pm

25.0mmSQR = 5.64190mm Diameter of metal conductor (plastic sheathing extra measurement)
16.0mmSQR = 4.51351mm
10.0mmSQR = 3.56825mm
6.0mmSQR = 2.76395mm
4.0mmSQR = 2.25678mm
2.5mmSQR = 1.78412mm
1.5mmSQR = 1.38198mm
1.0mmSQR = 1.12838mm

Accurate micrometer needed :)
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Postby johnnyuhtar » Mon Oct 15, 2007 8:23 pm

Thanks RowanMook
I went to my mates and grilled him about this (once again) he showed me a book Electrical Installations Calculations -(AJ Watkins) that is where he got his sums from I tried your therie and its much shorter but did get the same end figure when I apllied your pi number to his sum (just yours is easier!) I did measure the wire with digi vernia callipers to get the 1.7 if only had of showed me this book 5 days ago its got all the wire sizes in it !!!
What were the numbers next to the wire sizes you sent me matey ??
Thanks again for your time and help
Johnny
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