1. Switch-Mode DC-AC Inverters
Chapter 8
Switch-Mode DC-AC Inverters
converters for ac motor drives and uninterruptible power supplies
Copyright © 2008
by Jose Bastos
Chapter 8 Switch-Mode DC-
Sinusoidal AC Inverters

2. Switch-Mode DC-AC Inverter
Block diagram of a motor drive where the power flow is unidirectional
Copyright © 2008
by Jose Bastos
Chapter 8 Switch-Mode DC-
Sinusoidal AC Inverters

3. Switch-Mode DC-AC Inverter
Block diagram of a motor drive where the power flow can be bi-directional
Copyright © 2008
by Jose Bastos
Chapter 8 Switch-Mode DC-
Sinusoidal AC Inverters

4. Switch-Mode DC-AC Inverter
Four quadrants of operation
Copyright © 2008
by Jose Bastos
Chapter 8 Switch-Mode DC-
Sinusoidal AC Inverters

5. One Leg of a Switch-Mode DC-AC Inverter
full bridge converter (fig shows one leg)
The mid-point shown is fictitious
Copyright © 2008
by Jose Bastos
Chapter 8 Switch-Mode DC-
Sinusoidal AC Inverters

6. Square-Wave Mode of Operation
Harmonics are of the fundamental frequency
Copyright © 2008
by Jose Bastos
Chapter 8 Switch-Mode DC-
Sinusoidal AC Inverters

7. Effect of Blanking Time
Results in nonlinearity
Copyright © 2008
by Jose Bastos
Chapter 8 Switch-Mode DC-
Sinusoidal AC Inverters

8. Effect of Blanking Time
Effect on the output voltage
Copyright © 2008
by Jose Bastos
Chapter 8 Switch-Mode DC-
Sinusoidal AC Inverters

9. Synthesis of a Sinusoidal Output by PWM
Copyright © 2008
by Jose Bastos
Chapter 8 Switch-Mode DC-
Sinusoidal AC Inverters

10. Synthesis of a Sinusoidal Output by PWM (2)
Copyright © 2008
by Jose Bastos
Chapter 8 Switch-Mode DC-
Sinusoidal AC Inverters

11. Half-Bridge DC-AC Inverter
Capacitors provide the mid-point
Copyright © 2008
by Jose Bastos
Chapter 8 Switch-Mode DC-
Sinusoidal AC Inverters

12. Single-Phase Full-Bridge DC-AC Inverter
Consists of two inverter legs
Copyright © 2008
by Jose Bastos
Chapter 8 Switch-Mode DC-
Sinusoidal AC Inverters

13. PWM to Synthesize Sinusoidal Output
The dotted curve is the desired output; also the fundamental frequency
Copyright © 2008
by Jose Bastos
Chapter 8 Switch-Mode DC-
Sinusoidal AC Inverters

14. Bi-Polar Voltage switching
Copyright © 2008
by Jose Bastos
Chapter 8 Switch-Mode DC-
Sinusoidal AC Inverters

15. Uni-polar Voltage Switching
Harmonic components around the switching frequency are absent
Copyright © 2008
by Jose Bastos
Chapter 8 Switch-Mode DC-
Sinusoidal AC Inverters

16. Sinusoidal Synthesis by Voltage Shift
Copyright © 2008
by Jose Bastos
Chapter 8 Switch-Mode DC-
Sinusoidal AC Inverters

17. Programmed Harmonic Elimination
Angles based on the desired output
Copyright © 2008
by Jose Bastos
Chapter 8 Switch-Mode DC-
Sinusoidal AC Inverters

18. Summary of DC-AC Inverters
PWM
square-wave
Functional representation in a block-diagram form
Copyright © 2008
by Jose Bastos
Chapter 8 Switch-Mode DC-
Sinusoidal AC Inverters