High 3rd harmonic on the neutral

In the TP DB with SP circuits example (ignoring harmonics), what you might have at a particular snaphot in time for three nearly but not quite equal loads is: 50A flowing into the N bar from circuit 1's N, 15A flowing out from the N bar to circuit 2's N, 25A to circuit 3, and 10A flowing from the N bar back up the TP supply neutral. The N bar is nearly at earth potential, drifting by whatever voltage drop there is along the supply N to the earthing point due to the 10A current flowing along it.


Over the course of the cycle, the 50/-15/-25 vary, but always add up to +10 (which represents the load imbalance), so there's a constant 10A along the supply N. That's the beauty of TP; compared with 3 SP supplies -each with a full-size N - by combining the N conductors the currents mostly cancel each other out and the combined N can be a lot smaller, or indeed removed completely when you know the load will be fully balanced.

In the TP DB with SP circuits example (ignoring harmonics), what you might have at a particular snaphot in time for three nearly but not quite equal loads is: 50A flowing into the N bar from circuit 1's N, 15A flowing out from the N bar to circuit 2's N, 25A to circuit 3, and 10A flowing from the N bar back up the TP supply neutral. The N bar is nearly at earth potential, drifting by whatever voltage drop there is along the supply N to the earthing point due to the 10A current flowing along it.


Over the course of the cycle, the 50/-15/-25 vary, but always add up to +10 (which represents the load imbalance), so there's a constant 10A along the supply N. That's the beauty of TP; compared with 3 SP supplies -each with a full-size N - by combining the N conductors the currents mostly cancel each other out and the combined N can be a lot smaller, or indeed removed completely when you know the load will be fully balanced.