 In this video, we're going to talk about how to properly connect a multi-winding transformer. When we have a multi-winding transformer, we have two windings here. Two windings here. We have a high side and a low side. We determine what that is. For this video, we're going to have this be my high side and this be my low side. We'll consider this to be a step down transformer. There's two ways you can hook up a multi-winding transformer. You can either connect the windings in series or in parallel. We're going to walk through different connections. There's a right way to do it and a wrong way to do it. I want to walk through and show you both. I'll take you through the right way to do it and then I'll take you through the wrong way to do it and show you what could possibly happen. Now I've assigned some lead designations here. Again, we're just going to focus on the primary side right now, which is this winding right up here. Let me just get my pointer out. This winding right up here is my high side and it's connected to this bus up top here. We're going to make this our primary focus right now because it is the primary. I'll show you how we properly connect it. This is a series connection and I won't go into why you use a series connection. That'll be covered in another video, but it is important that we understand how to make the connection here. In order to make this connection, you have to have these windings connected properly. It's all about the polarity when you're dealing with a primary connection. If you have the wrong polarity, bad things can happen. Let's see what happens here. We're designating a polarity. I've got my negative line. I've got my positive line, which means that current is going to be flowing through this from negative to positive, which means that current is going to flow across my windings like this. It's going to start on the negative, work my way down through these windings, loop around and go across that winding and come out to the positive. Now with the primary, it's all about the lines of flux. What happens here is, as my current is flowing across this winding here, it loops around and flows that way as well. They're heading in the same direction, which means that the magnetic lines of flux, this flux and this flux is adding together, which creates an overall flux, which is important because keep in mind that a transformer, the windings are just wired, just wrapped in a coil. Because it's creating this massive amount of flux, it creates a big, huge counter EMF, which pushes back on the current. So we don't actually see hardly any current flowing across here. You'll see a minimal amount, two to five percent of your rated current flowing through this. But for the most part, we consider that to be negligible. We see no current flowing through here. So that's because this flux and this flux are adding together to create a counter EMF that pushes back on the current. Now the same thing holds when we're talking about a parallel connection. If you look at this here, I've got my H1 and my H3 leads are actually connected together. H2 and H4 connected together. So my current can get down to this point here, which is a node, and my current can split off and go out through this winding. Or it can go down through this winding. That's a proper parallel connection. So if we follow our current path again, what it looks like is, we've got, let me just pick a color here, we've got this current flows this way and out and current flows this way out. So we have the two windings together again heading in the same direction. So we get the flux adding, massive counter EMF pushes back on the current. Current doesn't short out. So this is a proper parallel connection. Let's see what happens when we have an improper connection. Here's a bad series connection. Now it is a series connection because you see that current flows down through this winding up around and goes down through this winding and out right from negative to positive. But if we look at it, look at the way that the direction flows. Current is flowing from down across here, and then it loops up and around and heads back this way. And so what's happening here is this guy, this current flows, this current flows creates flux that's heading this way and flux is heading this way. This flux opposes this flux and they oppose each other. And we call that bucking flux, which is fun to say, and it cancels out the flux. Well, if there's no flux, there's no counter EMF. If there's no counter EMF, there's nothing to oppose the current and the current shorts out, and we get what is commonly called in the electrical academy, kablazl flam, which is Dutch for melt your face off, which is actually just a word that I made up. You don't want to have that happen because what happens here is if all the flux cancels out here, you have no opposition to current flow. This definitely becomes a dead short. And if you don't have it properly fused, you could have an explosion. Worst case scenario, best case scenario, you have a fuse there and it just blows the fuse, which is probably more likely what's going to happen. So when we're dealing with our primary connection, remember, it is all about the polarity, the instantaneous polarity and the direction of current. So that's the main thing you have to take away from this first part of the video is on the primary connection and it's about the direction of current. Now let's look again at what happens when we have a bad parallel connection. So we have this happening where current comes down and it's heads this way and up and out, and then at the same time can head back this way up and out. So let's take a look at our current flow. It's flowing this way and then it's flowing back that way. That looks familiar, doesn't it? We have bucking flux happening again, which gives us what? Kablazl flam, exactly. You have a dead short again because you have no counter EMF, which means that you have nothing opposing the current in the primary, which means you're going to get a dead short again. So that is the primary connection. Again, it is all about the direction of current. Remember that. Now when we're dealing with the secondary, it's a little bit different. Secondary, we focus way more on the polarity, all right? And what I always tell my classes is this. You determine what the bus polarity is. So we've determined that's negative and that's positive. This polarity determines the polarity on the primary side and the primary determines the polarity on the secondary side, because we know that H1 and X1 will always have the same polarity. So following it through, we have here, this becomes negative here. H1 is negative, X1 is negative. H2 is positive, X2 is positive, H3 is negative, that's negative, H4 is positive, that's positive. So we have ourselves a decent connection here because what happens is your negative ends up being hooked up to a negative lead and your positive line ends up being hooked up to a positive lead and all is well. And the way I look at it is this. You have yourself two batteries that are in series. So because a transformer is a source of voltage on the secondary side, I say that this is a battery terminal, this is a battery terminal. So that's why I have them drawn up here. So I have X1 to X2 battery in series with X3 to X4. That's a good connection. So that we're looking forward to. That's how you do a proper series connection on the secondary side. If we look at our secondary parallel connection, very similar, this here is gonna be my negative, which means X1 is negative, which means that this line here is going to be negative. And then over here we got X4 being positive. X4 is positive here, which is gonna tie up to this line. And we have ourselves a good connection. Again, if we look at this like it's a battery, I've got this one here, this battery here, negative to positive is in parallel with this battery here, negative to positive. Let's see how that looks with the batteries. So negative positive, negative positive, that's a good connection because we have, these guys are helping each other out. If you need help on that, you need to go back to other videos on how we connect power sources or to connect DC power sources. But this is a good connection. Now let's see what happens when we have a bad connection. In this situation, I have X1 is negative, X1 is negative here, and we know that X2 is gonna be positive, X3 is negative, X4 is, or sorry, H1 is negative, H2 is positive, H3 is negative, H4 is positive, X1 is positive, X2 is, sorry, X1 is negative, X2 is positive, X3 is negative, X4 is positive. So I've got the negative line here and a negative line here. I have two similar polarities, which means that my line here is gonna have a negative and a negative. I will have a potential voltage here, but I have the same polarity here that means there's no potential difference from that side to that side, which is going to give me zero volts. Which basically makes it useless for me. It's like having a battery that is pushing back on itself. I'd say like have 120 volts here, pushing back on 120 volts there. It's dead to me down here, zero volts, useless. When I have this situation happening, what I have is current, sorry, instantaneous polarity and it works, but I have this situation where I have a negative and a positive, negative, positive. I get a negative here and a negative here, a positive here and a positive here. You're gonna get yourself a dead short. It's like having this battery here happening where I've got the negative positive, which connects to the negative positive. So basically here, these guys are gonna have a circulating current, which is gonna create this very little resistance in this because all you're dealing with is the lead resistance, which means you're gonna end up with what do you want to guess? Cablazol flam again. So it is very important that you understand how to properly connect these. Again, as I stressed before, on the primary side, it is all about the direction of current. On the secondary side, it's about the instantaneous polarity. When you're dealing with instantaneous polarity, you determine the line polarity. The line polarity determines the primary polarity. The primary polarity determines the secondary polarity, and that determines whether or not how you connect it down here. In another video, there'll be a test called the voltage closure test to determine what your voltage is that you're gonna read here so that you know that you have a safe connection. So make sure you check that one out.