1. Dept of Electrical & Electronics ELE 1001: Basic Electrical Technology Lecture 02 Resistance & Star-Delta Transformation ELE 1001: Basic Electrical Technology Lecture 02 Resistance & Star-Delta Transformation

2. Dept of Electrical & Electronics We will learn here…  Fundamentals of Resistor  Star & Delta connections  Star-Delta & Delta-Star Transformations

3. Dept of Electrical & Electronics Resistors  Resistance  Property which opposes the flow of current  R = V/I  Unit – Ohms (  )  Power P = VI = V 2 /R = I 2 R  Conductance  Reciprocal of resistance  Symbol: G  Unit – Siemens (S) R V I + -

4. Dept of Electrical & Electronics Resistivity & Temperature Coefficient For a homogeneous material: where, ρ= resistivity, l= length & a= cross-sectional area of the material where, α 0 = Temp coefficient of resistivity at 0°C R 0 = Resistance at 0°C Positive temp coeff: Aluminum, Copper, Gold, Tungsten Negative temp coeff: Carbon, Germanium (pure), Silicon (pure)

5. Dept of Electrical & Electronics Resistive Circuits  Resistors in parallel:  Resistors in series: R1R1 R2R2 R3R3

6. Dept of Electrical & Electronics Current Division in Parallel Circuits

7. Dept of Electrical & Electronics Voltage Division in Series Circuits

8. Dept of Electrical & Electronics Star & Delta Connections A B C R ab R bc R ca B C RaRa RbRb RcRc A Star ConnectionDelta Connection

9. Dept of Electrical & Electronics Star-Delta Transformation B C RaRa RbRb RcRc A A B C R ab R bc R ca  Delta to Star Transformation:

10. Dept of Electrical & Electronics Star-Delta Transformation contd…  Star to Delta Transformation: B C RaRa RbRb RcRc A A B C R ab R bc R ca

11. Dept of Electrical & Electronics Example 1 For the circuit shown, determine the power supplied to the resistive network ( all resistor values are in  ’s) P supplied =47.06 W

12. Dept of Electrical & Electronics Solution: Step-1

13. Dept of Electrical & Electronics Solution: Step-2 [ 47.06 W ]

14. Dept of Electrical & Electronics Example 2 Find the potential difference across 10Ω resistor. Also, find the power consumed by it. V 10Ω = 14.14V; P 10Ω = 20W

15. Dept of Electrical & Electronics Solution: Step-1

16. Dept of Electrical & Electronics Solution: Step-2

17. Dept of Electrical & Electronics Solution: Step-3

18. Dept of Electrical & Electronics Solution: Step-4

19. Dept of Electrical & Electronics Solution: Step-5

20. Dept of Electrical & Electronics Solution: Step-6

21. Dept of Electrical & Electronics Summary We started with  Resistance and its properties Then discussed  Resistive circuits  Current Division in Parallel Circuit  Voltage Division in Series Circuit  Star-Delta Transformation Concluded with  Application of star-delta & source transformation concepts.