1. Week 8 AC-to-AC Converters 1

2. Single-phase AC Voltage Controller 2

3. 3 Thyristor/Triac

4. 4 Single-Phase AC-AC Converter

5. 5

6. 6

7. 7

8. 8

9. Operation of a Single-phase AC Voltage Controller with (a) Single- pulse Gate Signal, (b) Multi-pulse Gate Signal 9

10. Definition of a Control Angle 10

11. 11

12. Fully Controlled Three-phase AC Voltage Controller 12

13. Thyristor Gate Triggering Generation of the firing signal The sawtooth waveform (synchronized to the ac input) is compared with the control signal v control, and the delay angle a with respect to the positive zero crossing of the ac line voltage is obtained in terms of v control and the peak of the sawtooth waveform V st.

14. Full-Bridge (Single- and Three- Phase) Thyristor Converters

15. Voltage and Current Distribution in a Fully Controlled Three-phase AC Voltage Controller: (a) Two Triacs Conducting, (b) Three Triacs Conducting 15

16. 16

17. Polarities of Output Voltages and Currents in a Fully Controlled Three-phase AC Voltage Controller in Mode 2 Before Firing Triac TA (solid line) and Following the Firing (broken line) 17

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19. 19

20. 20

21. Three-phase AC Voltage Controllers Connected Before the Load: (a) Half- controlled, (b) Delta-connected 21

22. Three-phase AC Voltage Controllers Connected After the Load: (a) Wye- Connected, (b) Delta-connected 22

23. Three-phase Four-wire AC Voltage Controller 23

24. Single-phase AC Chopper with an Input Filter 24

25. Waveforms of Voltages and Currents in a Single-phase AC chopper: (a) Output Voltage and Current, (b) Input Voltage and Current After the Input Filter, and the Fundamental Output Current 25

26. Control Characteristic of an AC Chopper 26

27. Wye-connected Three-phase AC Choppers: (a) Three-wire, (b) Four Wire 27

28. Delta-connected Three-phase AC Chopper 28

29. Changes in the Firing Angle in a Cycloconverter 29

30. 30

31. Three-phase Three-pulse Cycloconverter 31

32. Three-phase Six-pulse Cycloconverter with Isolated Phase Loads 32

33. Three-phase Six-pulse Cycloconverter with Interconnected Phase Loads 33

34. Three-phase to Three-phase (3  -3  ) Matrix Converter 34

35. Arrangement of 3  -1  and 1  -3  Matrix Converters, Equivalent to a 3  -3  Matrix Converter 35

36. State AAB as Realized by Activation of Switches in (a) Virtual Rectifier and Inverter, (b) Matrix Converter 36

37. 37

38. 38

39. Reference Current Vector in the Vector Space of input Currents of the Virtual Rectifier 39

40. Reference Voltage Vector in the Vector Space of Line-to-Neutral Output Voltages of the Virtual Inverter 40

41. Bidirectional Semiconductor Power Switches: (a) Two IGBTs and Two Diodes, (b) One IGBT and Four Diodes 41

42. 42

43. Switching Signals for Individual Switches in a Matrix Converter 43

44. 44

45. 45 Switching Characteristics

46. 46