 This video is going to be a walkthrough of how to handle a multi winding transformer when we're dealing with multi winding transformers We've got to deal with the turns ratio and we're going to get that based off of this 13.8 KV to 120 volt Rating here because again, it's winding to winding ratio. Now. You notice we have up here We have 102.5 percent. We have a hundred percent ninety seven point five percent and ninety five percent Those percentages we're going to apply to our turns ratio We are not going to apply them to the voltages It's very common for people to want to apply them to the voltages We're not going to do that in my method We're going to first off figure out what our hundred percent ratio is and our hundred percent ratio is based off of the 13.8 KV to 120 volts So our turns ratio works out to be 115 to 1 based off of 13,800 divided by 120 volts gives us the 115 to 1 this ratio is what we're basing everything else off of What we're going to do now is we're going to take a hundred and two point five percent of 115 to get our next ratio Which works out to be a hundred and seventeen point nine to one again all we did was take 115 and multiply it by a hundred and two percent point five percent or one point zero two five We're going to do that for the next one so we'll apply a hundred and fifteen to ninety seven point five percent and a hundred and fifteen to Ninety five percent to get the other two ratios as well So there we have our other ratios so again just to recap because it's very important We take the hundred percent ratio first we get that by going 13,800 divided by 120 to get the hundred and fifteen to one turns ratio Then we base these other taps Off of that hundred percent tap So a hundred and fifteen I go a hundred and fifteen times one point zero two five to get a hundred and seventeen point nine I take a hundred and fifteen times point nine seven five to get a hundred and twelve point one And I take a hundred and fifteen times point nine five to get a hundred and nine point three These ratios are the ratios we're going to be watching for and it's very important that we understand where they are So the first thing I always do is I always on a piece of paper Take my taps here And I put the ratios up Somewhere else so I have reference to them Now remember when we're dealing with a multi winding transformer multi tap on the top there We are decreasing our number of turns for the most part. I know we have this guy here But let's talk about these two here as we decrease our number of turns And the voltage up here on our primary state is the same We increase our volts per turn and remember volts per turn primary is equal to volts per turn secondary So that's why we use these taps if you want to increase your secondary voltage Because of a voltage terminal drop because you've loaded your transformer you go down on your taps you do not go up Which is why again we use these ratings here. Let's apply a voltage to the primary and see how this happens Let's apply 12 kv to the primary And let's see what we get. I'm going to show you if we take the 100 ratio what we get for the secondary So if we use the 100 ratio taking 12 kv, we're going to use 115 so we're going to go 12 000 divided by 115 to get my secondary voltage, which is 104.3 volts Not ideal. We would like to get closer to 120 We know that we can't go up Because we've just discussed how we need to take our turns ratios and decrease them to increase our volts per turn So we're going to use 97.5 or 95 percent. Let's try the 97.5 percent tap I'm going to take 12 kv on my primary and divide it by 112.1 and see what we get and we get 107 volts. So we're getting closer. Let's try the last one the 95 percent tap Let's see how close we can get to that 120 using the 95 percent tap again. We're going to take 12 000 kv divided by 109.3 to get a voltage of 110 volts so you can see as we're not at the 120 yet We'd have to go down further on taps if we had them But you're starting to see the method here that as we decrease our taps Our secondary voltage increases That's how these things work. So that's working from our primary to our secondary Let's talk about what would happen if I have a secondary voltage and we could work out what voltage was applied to the primary Let's say that we have 120 volts measured on our secondary side We want to find out what voltage was applied to the 95 tap on the primary To get that We're just working backwards just like we've always done. So we're going to go 120 And we're going to look at the 95 ratio, which is 109.3 to 1 we're going to go 120 times 109.3 to 1 and we get 13116 volts So it's just the same way we always dealt with we just have to really pay attention to which ratio we're going to use And the ratios we use are based completely off the taps The next one the last problem that we could come across in a situation like this is If I give you the primary voltage and the secondary voltage and I want you to tell me which tap we used So in this situation, I know that my primary voltage Is 12,880 volts I know that i'm getting a secondary voltage of 112 volts And I want to discover which of these taps am I using This is varies as lot easier than it looks because all we have to do is figure out what our ratio is We're going to take 12,880 and divide it by 112 volts. Let's do that first We work out that with 12,880 volts divided by 112 you get a ratio of 115 to 1 We want to figure out which tap that is let's go back up to this little chart. I've got up here. Which one is it? It's the 100 tap I'm using That's how we're doing it. You just take you work out your ratio and see which ratio lines up there and we're good to go That's multi tap windings. They're not that difficult Remember just base them all off of the turns ratio figure out what your 100 ratio is based off your rating of the transformer Then take each of these taps and apply them to the 100 ratio So I'll get after that you follow those steps. You will have no problem at all with multi windings See you in the next video