3 phase cable ques.??

[ahmed osama]

3 phase cable

Dear Sir

nice ques. , now always the 3 phase cable has 3 Live wire & 1 wire netural , now why always the guage the of the netural wire less than the main 3 live wires , although it carry the return currnet which it should have guage 3 times the live wire ??


thanks
bye

 

[trekkytekky]

3 phase cables

Only in single phase applications is the current in the neutral equal to the current in the active phase.

In a balanced three phase supply the neutral would carry no current, the sum of currents over the three phases would equal zero.

Quite often even in a three phase balanced application the neutral will carry currents due to harmonics and other issues, and if disconnected will not be exactly at 0 volts.

Even in an unbalanced application the current going into a circuit will flow out on at least one other phase, therefore reducing the demand of the neutral which would only carry the difference.

As a side issue not all neutrals are lower gauge and not all three phase cables have a neutral.

 

[FvM]

what is a 3 phase cable

I have a simple general suggestion: Try to get an intuitive understanding of 3-phase AC systems operation.
Chapter 10 (Polyphase AC circuits) of the below internet text book is a good introduction.

 

[drr]

cablage a troi phases

please sir (fvm) can helpe me another refrence about same subject

thank you

eng.ihssan
iraq -diyala university

 

[mostafa ahmed]

3 p cable

Dear Ahmed,
The current in the nutral wire not three time the live wire, but if there is a large harmonics, the current in it is large. Canada put the nutral wiral larger than the live wire.
Good luck.