Lecture 7- 2023 (4).pptx abcdefghijklmno

Electrical systemss

1. Nimsiri Abhayasinghe PhD(Curtin), MSc(Moratuwa), BSc Eng (Hons)(Moratuwa) EC1022 – Electrical Systems 1

2. Chapters 18-20 of the reference book 2 AC Circuit Analysis

3. Analyzing AC Circuits 3 We can use methods used in DC circuit analysis to analyze an ac circuit, with certain limitations. All phasors are represented with their rms values. All theorems learnt in DC analysis can be used as it is for ac analysis with all phasors in rms.

4. Ohm’s Law for AC Circuits 4 Resistors

5. Ohm’s Law for AC Circuits 5 Inductors Capacitors

6. AC Series and Parallel Circuits 6 Impedances Series Parallel

7. Example 1 7 Find Z T . Sketch the impedance diagram for the network and indicate whether the total impedance of the circuit is inductive, capacitive, or resistive. Use Ohm’s law to determine I, V R , and V C .

8. Solution 8 (a)

9. Solution 9 (b)

10. Solution 10 (c)

11. Example 2 11 Find the equivalent admittance and impedance of the network of the figure. Sketch the admittance diagram.

12. Solution 12

13. Solution 13

14. KVL & Voltage Divider Rule KCL & Current Divider Rule 14 Kirchhoff’s Laws

15. Frequency Effect 15 Reactance is frequency dependent. Therefore, RC, RL and LCR circuits behave differently at different frequencies – frequency dependent Read Section 18.7

16. Series – Parallel Conversion 16 Applicable only at a given frequency.

17. Example 17

18. Source Conversion 18

19. Example 1 19 Convert the voltage source of the figure into an equivalent current source.

20. Example 2 20 Convert the current source of the figure into an equivalent voltage source.

21. Mesh Analysis 21 Read and understand the steps in Section 19.3. Example: Solve for the loop equations in the circuit of the figure below.

22. Solution 22 Step 1 – Source Conversion

23. Solution 23 Steps 2 & 3 – Redraw the circuit and mark loop currents

24. Solution 24 Step 4 – Write loop equations

25. Solution 25

26. Solution 26

27. Nodal Analysis 27 Example: Given the circuit of the figure, write the nodal equations and solve for the node voltages.

28. Solution 28

29. Solution 29

30. Delta-to-Wye and Wye-to-Delta Conversions 30

31. Example 31 Determine the Y equivalent of the Δ network shown in figure.

32. Superposition Theorem 32 Example: Determine the current I in figure by using the superposition theorem. Solution: Current due to the voltage source  

33. Superposition Theorem 33 Current due to the current source  

34. Thévenin’s Theorem 34 Thévenin equivalent circuit Example: Find the Thévenin equivalent circuit external to Z L for the circuit

35. Solution 35 Steps 1 and 2:

36. Solution 36 The resultant Thévenin equivalent circuit

37. Norton’s Theorem 37 Norton equivalent circuit A similar approach to what we used in DC can be used here.

38. Norton’s Theorem 38 Source conversion can be used

39. Example 39 Given the circuit of the figure, find the Norton equivalent.

40. Solution 40

41. Solution 41