1. Lecture-5

2. Md.Kausher ahmed Electrical department

3. Electrical engineering-1 Code-6723

4. Lesson declared Star- Delta conversion

5. Learning outcomes After finished this lesson student will able to # Say what is star connection. # Say what is delta connection. # Explain star to delta connection Theorem.

6. Electrical circuit Sometimes we are not sure in electric circuits that the resistors are neither in parallel nor in series. See the circuit below here the relation between R 1 resistor and R 6 resistor is series or parallel we are not sure.

7. Continue,,,,,,,,,, In that case we can simplify this circuit using three terminal equivalent networks. Three terminal networks are used in three phase connection, matching networks and electrical filters.

8. Continue……… Figure 2 shows Wye (Y) and Tee (T) networks and figure 3 shows delta (∆) and pie (Π) network.

9. Delta to wye conversion It is easy to work with wye network. If we get delta network, we convert it to wye to work easily. To obtain the equivalent resistance in the wye network from delta network we compare the two networks and we confirm that they are same. Now we will convert figure 3 (a) delta network to figure 2 (a) wye network. From figure 3 (a) for terminals 1 and 2 we get,

10. Continue…… R 12 (∆) = R b || (R a + R b ) From figure 2 (a) for terminals 1 and 2 we get, R 12 (Y) = R 1 + R 3 Setting wye and delta equal, R 12 (Y) = R 12 (∆) we get,

11. Continue……

13. Equations (v), (vi) and (vii) are the equivalent resistances for transforming delta to wye conversion. We do not need to memorize these equations. Now we create an extra node shown in figure 4 and follow the conversion rule, Each resistor in the Y network is the product of the resistors in the two adjacent Del branches, divided by the sum of the three Del resistors.

14. Problem: convert the delta network to wye network. From equation (v), (vi) and (vii) we can find the equivalent resistance of wye network

15. Continue……. The equivalent Y network configuration is shown in figure 6.

16. Continue…….

17. Notice This lecture have not finished. It will finish at the next class. We will learn more thing. About circuit..