Three phase voltage source inverter

180 and 120 degree mode

1. THREE PHASE VOLTAGE SOURCE INVERTER Kongunadu College of Engineering and Technology T hree Phase VSI Contents: Inverter Introduction classification Three phase Voltage source inverter 180 degree conduction mode 120 degree conduction mode Applications References

2. INTRODUCTION An inverter refers to a power electronic device that converts power in DC form to AC form at the required frequency and voltage output. The ideal output of an inverter is a sinusoidal waveform. Such a wave gives continuous flow of power. But the output from the circuit is generally not ideal. It gives output in the form of square wave, quasi-square wave or PWM. The conversion of DC power to AC power can be done using two approaches. Both do conversion in two steps. In the first approach, a low voltage DC power is converted into high voltage DC power and then in the second step this high voltage DC power is converted to AC power. In the second approach, a low voltage DC power is converted to low voltage AC power and then this output is stepped up to high voltage AC power. Kongunadu College of Engineering and Technology Three phase VSI

3. classification Voltage Source Inverter (VSI)  − The voltage source inverter has stiff DC source voltage that is the DC voltage has limited or zero impedance at the inverter input terminals. Current Source Inverter (CSI)  − A current source inverter is supplied with a variable current from a DC source that has high impedance. The resulting current waves are not influenced by the load. Kongunadu College of Engineering and Technology Three phase VSI

4. Three phase voltage source inverter Kongunadu College of Engineering and Technology Three phase VSI

5. Cont… A three-phase inverter converts a DC input into a three-phase AC output. Its three arms are normally delayed by an angle of 120° so as to generate a three-phase AC supply. The inverter switches each has a ratio of 50% and switching occurs after every T/6 of the time T (60° angle interval). The switches S1 and S4, the switches S2 and S5 and switches S3 and S6 complement each other. The two types of inverters above have two modes of conduction −  180° mode of conduction  and  120° mode of conduction . Kongunadu College of Engineering and Technology Three phase VSI

6. 180 degree mode of conduction The load voltages are gives as follows; V AN  = V/3, V BN  = −2V/3, V CN  = V/3 The line voltages are given as follows; V AB  = V AN  − V BN  = V, V BC  = V BN  − V CN  = −V, V CA  = V CN  − V AN  = 0 Kongunadu College of Engineering and Technology Three phase VSI

7. Cont… Kongunadu College of Engineering and Technology Three phase VSI

8. 120 degree mode of conduction Phase voltages = Line voltages V AB  = V V BC  = −V/2 V CA  = −V/2 Kongunadu College of Engineering and Technology Three phase VSI

9. Cont… Kongunadu College of Engineering and Technology Three phase VSI

10. Applications Dc power source utilization Un interruptible power supplies Induction heating Variable frequency drive Electrical vehicle drive Kongunadu College of Engineering and Technology Three phase VSI

11. References M.H.Rashid , ‘Power Electronics: Circuits, Devices and Applications’, Pearson, PHI Third Edition, New Delhi, 2004. P.S.Bimbra “Power Electronics” Khanna Publishers, third Edition, 2003. https://www.tutorialspoint.com/power_electronics/power_electronics_types_of_inverters.htm https://www.theengineeringprojects.com/2016/10/introduction-inverters.html Kongunadu College of Engineering and Technology Three phase VSI