1. POWER ELECTRONICS Instructor: Eng. Jalal Al Roumy The Islamic University of Gaza Faculty of Engineering Electrical Engineering Department بسم الله الرحمن الرحيم EELE 5450 — Summer 2012 Lecture 21

2. HALF-CONTROLLED BRIDGE WITH RESONANT LOAD If the resonance is to continue for most of the half-cycle in order to reduce the current harmonic content, the value of 1/a = t, the time constant, must be a significant part of the half-cycle period.

3. HALF-CONTROLLED BRIDGE WITH RESONANT LOAD Example

5. HALF-CONTROLLED BRIDGE WITH RESONANT LOAD Example

6. THREE-PHASE BRIDGE INVERTERS A full-bridge three-phase BJT inverter is shown. The load is a balanced star connection of pure resistors. If the load was inductive, feedback diodes would be connected across each switch; these could be built into the switch module. In this type of inverter, two or three switches could be conducting simultaneously.

7. Two switches conducting The conducting sequence is as follows (each device conducts for a 120 o period):

8. Two conducting devices- line voltage and current Values of line voltage and line (also phase) current for 60 o intervals are shown, from which the waveforms are constructed. The other two lines have identical values, displaced mutually by 120 o

9. Two conducting devices- line voltage and current Values of line voltage and line (also phase) current for 60 o intervals are shown, from which the waveforms are constructed. The other two lines have identical values, displaced mutually by 120 o

10. Two conducting devices- line voltage and current

12. Three switches conducting The conducting sequence is as follows (each device conducts for a 180 o period):

13. Three conducting devices- line voltage and current Values of line voltage and line (also phase) current for 60 o intervals are shown, from which the waveforms are constructed. The other two lines have identical values, displaced mutually by 120 o

14. Three conducting devices- line voltage and current Values of line voltage and line (also phase) current for 60 o intervals are shown, from which the waveforms are constructed. The other two lines have identical values, displaced mutually by 120 o

16. Comparing rms line currents

17. End of Lecture