Michael15956
Senior Member
- Location
- NE Ohio
I understand the principles of current canceling out in the neutral and only the unbalanced current is returned to the transformer. Well, maybe I think I understand. So, in circuits without a lot of harmonics the neutral can be reduced in size proportional with the phase conductors. Now, I'm trying to imagine this current flow. I believe I understand the current flow in a single phase 240v circuit with just two phase conductors and no neutral. The AC comes from one phase conductor and returns through the other phase conductor and then reverses itself 60 times per second. I imagine this as current starting out in one phase conductor, I will name L1, going through a load and then back to the transformer through L2. Then going back to the load through L2 and returning back to the transformer through L1, and then reversing itself again 60 times a second.
Now, I was also told that this is exactly what happens in a 120V load. The same reversing at 60 times per second, but in this circuit it is the neutral conductor not another phase conductor. So in a 120V unbalanced load situation with two or more circuit branches is the cancellation occurring in the neutral where only the unbalanced load returns back to the transformer and the rest of the current returns back to the load through the neutral conductor?
Second question: If the above is correct is this the reason why in T250.66 the code allows the neutral to be reduced in size proportionally to the phase conductors?
TIA
Now, I was also told that this is exactly what happens in a 120V load. The same reversing at 60 times per second, but in this circuit it is the neutral conductor not another phase conductor. So in a 120V unbalanced load situation with two or more circuit branches is the cancellation occurring in the neutral where only the unbalanced load returns back to the transformer and the rest of the current returns back to the load through the neutral conductor?
Second question: If the above is correct is this the reason why in T250.66 the code allows the neutral to be reduced in size proportionally to the phase conductors?
TIA