 In this video, we're going to be going over the three phase theory. We're going to be talking about the y or star configuration and determining what the current on a neutral will be if there's a balance system. And by balance system, I mean that all three phases will be seeing the same current. Here we have our standard y system or star system. We have phase coming in this direction, phase coming in this direction, phase coming in this direction. And we have our neutral, which will be going out on that direction. So we have a neutral or a star point right about here and that will determine where we're going to be getting our current from. So the first thing I want to do is I want to name all these phases. We'll call this phase A. This will be our neutral, obviously. This phase B and this phase C. Now again, if you understand how single phase neutrals work, the neutral carries the unbalanced current. So we're going to see what happens in a three phase system. It's the same principle. It does carry the unbalanced current. First thing I do, if you watched any of these videos, you know that I put in instantaneous polarity. So because this is a load, the current will be flowing from negative to positive, negative to positive, negative to positive. And again, for you purists out there, I understand that each one of these is not going to be happening at the exact same time, that they're going to be happening 120 degrees out of phase. But for simplicity's sake and for the math's sake, we're just going to stop time and say that they're all happening at equal time. Now let's say I'm just going to use 12 amps as an example. I have 12 amps coming in on my A phase, 12 amps coming across on my B phase and 12 amps coming across on my C phase. And we'll talk about what my neutral current is going to be in just a second here. Again, as always, we put up our X, Y chart over on this side because we need to take these guys, these currents are going to be coming in at different vectors, which means we can't add them up arithmetically. We can't just add 12 amps to 12 amps. What we have to do is we have to convert them into their X and their Y coordinates, watch my video on vectors and especially on vector addition. We'll explain to you why that is. But for right now, just trust me in the fact that we are going to be converting each one of these 12 amps into its vector coordinates based on the angle it's coming in at. So let's start with the easy one. 12 amps on the B phase here. We're coming in hot. We're coming across here, so I'm going to go negative 12 because I'm starting here. So I'm going to go negative 12 times the cos is going to of zero is going to give me negative 12. Negative 12 times the sign of zero is going to give me zero on this phase here. I do the same thing on this A phase here. We're going to add it in. So I'm taking 12 amps. It's going to be negative 12 times the cos of 120 gives me 6 and negative 12 because that starts at the negative and ends up positive there. Negative 12 times the sign of 120 gives me negative 10.4. Again, 120 degrees out of phase with each other with their people. So that's why I'm using 120 degrees. And again, if you're wondering where the sign and the cos are coming from, watch the video on vectors. Just go to the playlist on trigonometry and we'll explain it all to you there. Then we get our last one here. So we've got negative 12 times the cos of 240 gives you 6. Negative 12 times the sign of 240 gives you 10.4. So we add all those up and negative 12 plus positive 6 plus positive 6 is zero and zero plus negative 10.4 plus 10.4 gives you zero. So that's determining what our current is. We've got a zero on the X and a zero on the Y and I don't think you need to be a mathematician to determine that the resultant of this is going to be zero amps. So in a balanced Y or star configuration your neutral current is going to be zero. In another video, I will go through what the current will be in an unbalanced circuit but in a balanced Y configuration your neutral current will be zero.