hello and welcome to another edition of Sparky help and this time we're going to be looking at the easy guide to Star and Delta electrical connections so first of all let's look at the shape of a sine wave for a single phase Supply this time it is one cycle of a 230 volt UK 50 hertz Supply not that matters what the frequency is but you can see that obviously the shape of the voltage looks like why do we need to look at this well we need to understand the concepts of a three-phase so on a three-phase supply we have three identical sine waves as we can see here L1 L2 and L3 which is the brown black and gray UK colors and we've got one single sine wave for the L1 and we can see that L2 starts 120 degrees after L1 does and another 120 degrees beyond that we have the start of L3 the reason for this is when generating the coils are displaced by 120 degrees therefore the understanding of this is to recognize that it takes time before each one reaches a peak value therefore this is why when we do 230 volts and we put it together with another phase of 230 volts we don't end up with 460. understanding that they are out of phase of each other by 230 volts identical sine waves identical frequencies will help us to understand how we add them up so let's look how we add them up so the best way to do this is we can show this by phaser Edition a phaser Edition or a phaser is a representation of the sine waves we were just looking at so we're going to look at the phasor addition of a 230 volt Supply we're going to draw this to scale using a scale of one centimeter equals 20 volts and then drawing from left to right we can draw to the scale a value and RMS value of 230 volts that comes in at 11.5 centimeters that gives us L1 to add L2 that will be 120 degrees apart and we're going to say the RMS value for that one as well so that is also 11.5 centimeters in length for L2 how do we add them up well because they're out of phase this by doing this method this will take into that consideration the out of phase part and we literally draw a line from one point to the other and if we do that L1 L2 added together is approximately equal to 19.9 centimeters why are we doing this well for this reason we can just quickly show you what the ratio would be and we can look at its 19.9 divided by 11.5 which are the values that we had on there originally and that comes to a value of 1.73 or as we will use root three root 3 is the standard number that is used in three-phase installations which is 1.732 and so on and so forth on the calculator but 1.73 1.732 is close enough but it's the ratio we're interested in this is not the only way it could be calculated here I've got a version that I did and you can see the one we've just done there which is that one as you can see it pointing towards it but it could also be done by referring these back to the other side and drawing it this way and then you add these two up and you can do it by compass and this value here is the same as that value there so this is an alternative method just in case you're looking at different work different ways of doing it a good with the compass method is that if they're out of phase by any other amount then it also works so what wave can we connect this up we can connect in star or Y connection most commonly known as a star connection for us anyway so how do we connect this up so here we've got three coils these could be resistors they could be capacitors one end of each is connected to the center point which is indicated as shown here and we connect them together and then the other end of each of them which I have drawn out in a star connection with 120 degrees apart but it doesn't have to be and obviously if you saw these connected you wouldn't necessarily know you'd have to read the nameplate for something but it's easier to draw and representation is easy to see and then we connect L1 L2 and L3 to it and it's recognizing what the voltages and currents are that we get from each of these so we have something called the phase current well if I said to you first of all where are the phase windings hopefully everyone would point to what I'm pointing to now it's these things here these are your phase windings so therefore it makes sense then that if the current that would flow in those would also be in those windings as well so we call these the phase currents and this is shown a current going out but it could equally be going in and there would be one in each one and if this is a balanced load and a balanced load means that all these coils are identical which is what you'd probably want then these values will be the same we've also got something called the line current so what's the line current the line current is typically in these lines here the L1 L2 the connect the cables that connect to them and these are our line currents at which we indicate there and again there's a shown flowing out and there'd be one in each one as well now if I was to ask you if there was some current flowing here let's say five amps when it goes around this corner it will also be 5 amps so what can we say about that well we can say we're in a star connection the IL equals I phase you probably think that makes perfect sense and hopefully it does and that would be the same for all star connections that gives us the next one then the phase voltage the phase voltage well again if I said to you I've whereabouts are the phases we would come back to these points here a voltmeter has two connections where do you connect it well one would connect to the end of the winding the other one connects to the other end of the winding which in this case is the center point the star point now the thing is people often think well it must have a neutral it doesn't need a neutral you just need access to this point I'm not saying you can always get to it when people make electrical machines you might not be able to get to that particular point but on paper theoretically we can so this would indicate the phase voltage and there'd be three of them but we're talking about equal load so they would be the same for each one so this is the phase and it's from the end of a winding down to the star point that leaves us one more to do and that is the line voltage VL and line voltage which is a measurement between lines of which there would be three combinations between L1 and L2 L1 and L3 and L2 and L3 and if hopefully they would all be the same so there is the L of a particular star connection the relationship between these is they won't be the same value which one will be larger well that will be the v l it was once pointed at me they were a student told me they remembered it because VL is larger and in this case that is true so how much larger well it's root three so that root three do we looked at a while ago is VL is equal to V phase times root three and that would give you the value of this voltage here so hopefully this is nice and simple and relatively easy to understand now let's have a look at a Delta connection so here we have a Delta connection we have three coils again three identical coils all connected in a Delta connection and Delta in the Greek letter the capital letter Greek letter which is a triangle so hence this is drawn in a triangle shape again in reality manufacturers when they build it into a machine you wouldn't know it's in a triangle shape because it's not really in a triangle though they're just connected but it's easier show to representation as we show it here and we've got the connections at each point end of each coil and then take a line off we don't have a center point so even if you wanted to there is nowhere to take a neutral to this anywhere so there is no way a neutral can go to these particular circuits so we need to identify the phase current the phase current again is in the phase winding so these are windings so the currents will be in these locations current can flow in or out whether this is a a load or a generator or some description so where would they be where we have one phase current there and we have another phase current going there so we have the phase currents the line current where does that go well as before it goes in the lines itself over here or in there there'll be three of them and hopefully these would all be balanced loads so we can recognize that so there's the line current what's the relationship between the two well to do that we need to look in and zoom in on this point at this location so let's just do that the current goes in the current goes in and a current comes away now if we were earlier on in our career and looking at a knowledge that we'd learned Kirchoff would have told us we had 10 amps and 10 amps and he would have said or you would assume it to be or from your knowledge early knowledge that that phase plus that phase equals IL and therefore 10 plus 10 is 20 but what we do know is that's wrong that's not correct because remember these are out of phase so the actual reason why kirchhoff has his name associated with this because he recognized that 10 plus 10 equals 17.32 amps oh where does that 17.32 comes from well it's the root three you're wondering what the lines represent they represent the phasor sum so to recognize the fact that they're not literally added so hence not 20 something else needs to be done you need to take in the angle between the two currents into consideration before adding them we go back to our original drawing on the Delta then so IL is equal to iphase times root 3 that root 3 factor which we're just going to use from here on in on all calculations where required the phase where's the phase voltage World in order for the measure of voltage there must be two points and again we're going to identify those points and it's from the one end of the coil in this case to the other end of the coil that would be the phase voltage that leaves one more left and that's the line voltage well the line voltage be measured and well it would be between any two lines again and it could be a one to L2 L2 to L3 or L1 to L3 and that would be that location there what can we tell you well if we're measuring the voltage in this location here if we've moved the arrows up and move them down then the difference between V phase and VL is absolutely nothing hence the formula is VL equals VP so there we have it these are the star and Delta formulas that can be applied to all circuits please watch out for my video on Star and Delta calculations to apply them thank you very much