Confusion in calculating neutral amperage.

[rotmgbetter]

Lets say I have a 3P 4W system and all the loads are balanced by line to neutral, I get that the final neutral current should be zero. However, what if we take into consideration each system by itself, shouldn't there be a neutral current?

Lets say we have switch and downstream of the switch we have A-N, B-N, C-N loads all at 100 amps. I understand that upstream of the switch the neutral will carry zero amps. However, for each individual connection for A-N, B-N, C-N the individual neutrals will be carrying a current. Therefore, do I need 300 amps worth of conductor downstream of the switch if they don't all run at the same time? The solution seems to be to bring 100 amps worth of neutral and then connect all of them together but what would this termination look like?

Obviously this seems wrong but how does it work in practice? By just teleporting this switch infinitely far away or at the point of connection, we see that the neutral should always carry zero current but its still confusing?

Thanks!

 

[ptonsparky]

Don't forget to do your NEC load calculations first. They will set the minimum size of the neutral at the point of common connection for the feeder. Each Phase to Neutral would be sized to the 100 Amp.

 

[ptonsparky]

The max imbalance with resistive loads would be 100 amp.

	1PH	3PH WYE	L-N Loads	L-N Loads
NEUTRAL LOAD	0.00​	100.00​	n	y
L1 AMP (1PH)	100.00​
L2 AMP (1PH)
L3 AMP	100.00​