How to calculate condoctor size for different types of load like resistive load, inductive load or capacitive load etc and what will be neutral wire size for these load?
Any body please help me.
Answers and Replies
From a conductor standpoint - ONLY current matters, the type of load does not. From an insulation standpoint ( material or type of wire) - in general voltage matters, but temperature and environment help to define the type (THHN for example) .
I agree with windadct about importance of total current [absolute value] in order to start with
the minimum conductor cross section from the temperature rise-losses and heat evacuation are
important. However, in my opinion, the voltage drop it is important too and it could require to
increase the cross section.
The voltage drop depends on power factor[cos(fi)] and reactance of the cable also.
For resistive load cos(fi)=1 [fi=0] and sin(fi)=0 If the circuit is entire inductive or entire capacitive the above formula does not change.
The neutral current is the same as live for single-phase system so you have to double the voltage drop.
In three-phase and neutral system only unbalance current will flow through neutral and the
cross section of the neutral is limited to ½ of live.
For voltage drop you have to multiply the above formula by sqrt(3).