2. Introduction
Conversion of available DC source into AC of variable frequency is accomplished by force commutated inverters.
The frequency of AC at output can be varied by controlling the conduction period of thyristors.
Output voltage of inverter has periodic waveform that is not sinusoidal but can be made to closely approximate this desired waveform.
Inverters are used in industrial applications, including speed control of induction and synchronous motor, aircraft power supplies, uninterruptible power supplies (UPS), and high-voltage DC transmision.

3. Half-Bridge Inverter

4. Square-wave output
Step-wave output

5. Voltage Source Inverter (VSI)

6. Half-Bridge VSI

7. Example 10.1

8. Full-Bridge VSI
State S1 S2 S3 S4
Output Voltage 1 On
Off +E 2 -E 3 4

10. Square-Wave output
With Inductive RL load

11. Step-Wave output

12. Inverter Voltage Control Techniques
1- Control of DC input voltage supplied to the inverter
2- Control of AC output voltage of the inverter
3- Control of the voltage within the inverter

13. Pulse-Width Modulation

14. (A) Single Pulse-Width Modulation

15. (B) Multiple Pulse-Width Modulation
Variable duty cycle with
m= 5
m= 2
m= 3

16. (C) Sinusoidal Pulse-Width Modulation

18. PWM Inverters
Single-phase Full-Bridge Inverters