 Hello, everyone. Welcome to a video lecture on star delta conversion. Myself, K. R. Berather, assistant professor, Department of Electronics and Telecommunication Engineering, Walsh and Nistap Technology, Swalapur. Let us start with the learning outcomes first. At the end of this session, you will be able to convert star to delta and delta to star transformations. These are the contents. Start with introduction, star and delta connections, star to delta transformations, delta to star transformation, problems and lastly reference. Introduction, the star delta transformation is another technique useful in solving complex networks. Basically, any three circuit elements, that is, resistive, inductive or capacitive may be connected in two different ways. One way of connecting these elements are called star connection or the y connection. The other way of connecting these elements is called the delta connection, star and delta connections. You can see the figures, the schematic of star and delta connection. Figure one is a schematic diagram for star connections. There are three terminals A, B, C and the resistors which are connected like a star, the resistors R A, R B and R C. The schematic diagram for delta connections between the terminals A, B, C, the resistors R, A, B which is connected between the terminal A and B, R, B, C which is a resistor connected between the terminals B and C, R, C, A which is a resistor connected between the terminal C and A. All these resistors R A, B, R B, C and R C, A are connected like a delta structure, star to delta transformation. How we are going to transform from the star to delta connection? If star is given, then you can easily convert into a delta connections. First we have given the star connections having terminals A, B, C, the resistors R A, R B and R C are connected in like a star. We need to convert this one into a delta connection. In the delta connections again between the terminals A, B, C, R A, B, R B, C and R C, A are connected. Now we need to find the values of R A, B, R B, C and R C A using R A, R B and R C. The formulas are R A, B equal to R A plus R B plus R A, R B divided by R C. So, between R A, B what are the resistors? R A and R B comes and R C is at the denominator. Similarly, R B, C equal to R B, C is resistor between the terminals B and C. This is equal to R B plus R C plus R B, R C divided by R A. Similarly, R C, A equal to R B plus R A plus R C, R A divided by R B. Once if you know the values of star connections R A, B, R C and equivalent delta connections R A, B, R B, C and R C A can be calculated. In this slide we shall see how to convert delta to star to R B. Now, we can see it has given there is a delta connection between the terminals A, B and C R A, B, R B, C and R C here are given, but equivalent star network we need to find. That is between the terminals A, B, C we need to find the values of R A, R B and R C for given value of R A, B, R B, C and R C A. The formula used to find the values of R A, R B and R C are R A equal to R A, B, R C A divided by sum of R A, B, R B, C and R C A. Similarly, R B equal to R B, C, R A, B divided by R A, B plus R B, C plus R C A. Lastly, R C A equal to R C A into R B, C divided by R A, B plus R B, C plus R C A. These are the formulas to find the equivalent star connections and their values R A, R B and R C are a given value of R A, B, R B, C and R C A in the delta network. Let us see a problem. A delta section of registers are given in the figure. Convert this into an equivalent star section. So, delta sections having A, B, C are the three terminals. There are three registers R 1, R 2 and R 3 having the values R 1 equal to 3 ohm, R 2 equal to 9 ohm and R 3 equal to 6 ohm. This delta connection we need to identify the equivalent star connections. So, I have taken R 1 here between the terminals B, C that is R B, C is equal to 3 ohm and between the terminals A, C, R A, C equal to 9 ohm and it is also equal to R C A and R A, B which is equal to 6 ohm. The delta sections have given in the figure. Convert this one into an equivalent star section. The formula used to convert the equivalent star section R A is equal to R A, B, R C A divided by R A, B plus R B, C plus R C A which is equal to R A, B is 6, R C A into 9. R A, B is 6 and R C A is 9 divided by sum of these three registers 6 plus 3 plus 9 which comes out to be 3 ohm. Similarly, R B equal to R B, C into R A, B divided by R A, B plus R B, C plus R C A which is equal to R B, C is 3 R A, B is again that is 6 divided by sum of 6 plus 3 plus 9 which comes out to be 1 ohm. R C is equal to R C A into R B, C divided by R A, B plus R B, C plus R C A. R C A is 9, R B, C is 3, 9 into 3 divided by sum of these three registers 6 plus 3 plus 9 which is equal to 1.5 ohm. Here there is a reflection side. Delta connection is also known as the options are y connection, mesh connection, third one either y connection or mesh connection, fourth one neither y connection nor mesh connections. Pause the video, try to think and answer for this question. I hope you might be getting an answer. The delta connection is also known as mesh connections because so delta connection have a close loop mesh or close loop path. These are the references used to prepare the above P P T. Thank you.