Neutral Conductor Current: How is it Possible?

[Manoj Sahu]

I read in a book that during normal working condition (balanced system) the current through a neutral conductor is zero i.e., Ia+Ib+Ic =0 where Ia, Ib, Ic are phase current of three different phases a, b, c. How is that possible? I mean if you look at mathematical result of the phases they are parted by 120' each.

 

[cnh1995]

In a balanced three phase system, neutral current is always zero.

I mean if you look at mathematical result of the phases they are parted by 120' each.

Plot the phasor diagram and see the resultant. It should be zero.

In your thread title, you've mentioned residential load. Residential supply is single phase supply and the neutral carries the same current as the phase wire.

 

[jim hardy]

I read in a book that during normal working condition (balanced system) the current through a neutral conductor is zero i.e., Ia+Ib+Ic =0 where Ia, Ib, Ic are phase current of three different phases a, b, c. How is that possible? I mean if you look at mathematical result of the phases they are parted by 120' each.

?? How is it possible?" you ask ? Do vectors add head to tail?
Get out your drafting tools and add three of equal length separated by 120 degrees .
You'll wind up back where you started, at the origin 0, 0

In your thread title, you've mentioned residential load. Residential supply is single phase supply and
within any single branch circuit- jh
the neutral carries the same current as the phase wire.

On the incoming wires from the pole to the beaker panel , neutral carries the difference between currents on the two phase wires, in other words the imbalance, just as in three phase.

 

[cnh1995]

Thanks @jim hardy for that edit.

On the incoming wires from the pole to the beaker panel , neutral carries the difference between currents on the two phase wires, in other words the imbalance, just as in three phase

I was talking about Indian supply system: 230V with one hot and one neutral.
So our residential neutrals never carry zero current.

But as you said, phase and neutral currents are equal indeed "within any single branch circuit".

 

[jim hardy]

I was talking about Indian supply system: 230V with one hot and one neutral.

Ahh that never dawned on egocentric me ! [ Sheepish grin icon ]