Cable Calculations 1

[140668]

I would like to know the complete procedure of carrying out cable calculatiions from the incoming transformer of an installation through a sub-distribution board, onto a number of distribution boards and finally down to final circuit, i.e. motors etc.. Can anyone help with a step by step procedure.

Many Thanks

 

[gaju]

Hi,
you have to start from the last load, find out the voltage level and divide the impedance so that u get current. Now, the easiest way is suppose you have five motors connected to a secondary of transformer. I suppose that the motors rating is 35 A, 10 A, 40A, 100A, and 55A. you have to select the cable of 1.25 % higher rating for safery purpose. now in this case you have to use the cable of rating 45A, 12.5A, 50A, 125A, 70A cables. the cable from transformer to panel is tha addition of these cables, i.e. 302.5A. I hope you got ur answer
Gaj

 

[busbar]

A good text is Beeman, Donald, Industrial Power Systems Handbook, McGraw-Hill, 1955 ISBN: 0070043019

Also, IEEE Standard 141-1993, Recommended Practice for Electric Power Distribution for Industrial Plants “Red Book” ISBN: 1-5593-7333-4