1. Chapter 3 Power Electronic Circuits

2. Converters
AC/DC
DC/DC
DC/AC

3. w t
Single-Phase, Half-Wave, AC-to-DC Conversion for Resistive Loads i vt v s a b

4. Single-Phase, Half-Wave, AC-to-DC Conversion for Resistive Loads

5. w t i vt v s a b

6. V
ave p a

8. Root-Mean-Squares (RMS)

9. Root Mean Squares of f
Step 2:
Step 1:
Step 3:

10. Concept of RMS v2 w t v Average of v2 Square root of the average of v2

11. Root-Mean-Squares (RMS) of a sinusoidal voltage

12. RMS of load voltage

14. This looks like
the negative
of the average
voltage across
the load. Why?

15. Electric Power: Method 1

16. Electric Power: Method 2

17. Power Factor (No Harmonics)
Real Power
Zero average

19. Effect of Harmonics
Fundamental
Component
of Current

20. Single-Phase, Full-Wave, AC-to-DC Conversion for Resistive Loads

21. When VAB > 0

22. When VAB < 0

26. Half Wave Versus Full Wave
Average Voltage
RMS Voltage
Power

27. Example
A full-wave, ac/dc converter is connected to a resistive load of 5 . The voltage of the ac source is 110 V(rms). It is required that the rms voltage across the load to be 55 V. Calculate the triggering angle, and the load power.

28. Solution

29. Purely inductive load

30. Power: Purely Inductive Load

31. Inductive Load w t vs i

32. Switched Inductive Load

33. Switched Inductive Loadvs w t i a b

34. w v t i v R t v L s v

37. - Relationship

39. v v i w t t Keep in Mind: s Current extends beyond 180o
Load Voltage goes negative s v

40. Free-Wheeling Diode

41. Free-Wheeling Diode
When vs is positive
When vs is negative

42. Free-Wheeling Diode i d i S a p b v S
From  to 
From  to 

43. Free-Wheeling Diode
From  to 

44. Free-Wheeling Diode
From  to 

45. Load Voltage exists between  and  onlyp b v S
Load Voltage exists between  and  only

46. 3-phase, AC/DC Conversion: Circuit

47. 3-phase, AC/DC Conversion: Switching Sequence

48. 3-phase,
AC/DC
Conversion
When S5 and S6 are closed

49. Advanced
Triggering

51. DC-to-DC Conversion
1. Step-down (Buck) converter: where the output voltage of the converter is lower than the input voltage.
2. Step-up (Boost) converter: where the output voltage is higher than the input voltage.
3. Step-down/step-up (Buck-Boost) converter.

52. Step Down
Time V S V CE S I + - l V l t t on I
Time t t on

53. Example
Solution

55. DC/AC Conversion – Single PhaseQ 1 2 3 4 I A B MM Q 1
and Q 2
are on 3 4
Time
Load voltage
VAB

56. DC/AC Conversion – Three-phaseMM

58. El-Sharkawi@University of Washington
First Time Interval
of Washington

59. El-Sharkawi@University of Washington
Second Time Interval
of Washington

60. Voltage Waveforms Across Load
Waveforms are symmetrical and equal in magnitude
Waveforms are shifted by 120 degrees

62. Control Parameters
Frequency
Voltage
Sequence
Voltage/Frequency

63. Frequency Control
F = 1/
 =  t = 6 t 

64. RMS Voltage

65. Voltage control - Fixed Width ModulationQ1
Time

66. Voltage Reduction VR

67. Reverse the terminal sequence abc to acb
Sequence Change
Reverse the terminal sequence abc to acb

68. Pulse-Width Modulation

69. Switching of Phase a

71. Textbook Correction
Amplitude Modulation

72. Energy Recovery
Voltage drop across switch

73. Charging

74. Discharging

76. Three-Phase energy recovery system

77. Current Source Inverter

78. Function of the diodes