balancedbattery-chargingharmonicsneutralthree phase
Talking about both three-phase AC as well as DC fast charging (wherein 3 phase AC is converted to DC) in EVs, I think that the 3-phase rectifier represents a balanced 'load'. Therefore I want to know why is then a neutral required? I ask this because I think that doing away with neutral would mean getting rid of the triple-n harmonics. Is my thinking correct?
Here is a type 2 connector pinout for reference:
The circuit will both be at higher voltage (well the parts of it) and will self-adjust. The reasoning behind this is pretty simple: First, the phases are out of phase, or to explain it simply, their voltage peaks happen at different times, so while one is at its maximum voltage, the two other phases will be at lower voltage than the one at maximum is, so basically, the load will be at the voltage between phases. Since we don't have the neutral conductor, the current which was going through it will have to go through one of the phases and that's how the circuit will "self-adjust". You can see that from the simulation here.
When the switch is closed, all 3 loads are at the same voltage of 5 V compared to the ground. Once the switch is open, the voltages at the loads will change. So the lightest load will drop the least voltage and the greatest load will drop the most voltage.
Maybe you can add a high impedance path to the neutral, like this:
simulate this circuit – Schematic created using CircuitLab
This works for me when i want to simulate a 3 phase rectifier.
Best Answer
Who says a Neutral 'is required'?
What you've drawn is a standard 3 phase connector. The standard connector always includes a neutral, because then it can be used for single phase and unbalanced loads, as well as balanced 3 phase loads. The cost of an extra pin and extra wire for the neutral is far outweighed by the improvement in flexibility for use of the connector.
It's easy enough to design any specific rectified load, whether charger, motor, whatever, to use only 3 phase with no neutral. It's a waste of time to insist that it can only be plugged into sockets without a neutral, as this would severely limit where it could be used.
It's quite possible, and this may be my first cut at a fast charger, to run the power DC from a full bridge rectifier on the 3 phases, but the control electronics from a small transformer running from a single phase and neutral. It's possible to list all sorts of practical advantages to such a split.