1. EE631 – Spring 20051 ECE631/EE631Q Lecture 9 – The Rectifier S.D.Sudhoff Purdue University

2. EE631 – Spring 20052 Restrictions on Firing And Commutation Let’s think about the a- phase current

3. EE631 – Spring 20053 Restrictions on Firing and Commutation Angle Thus, we must have –(1)  >0 –(2)  +u< 

4. EE631 – Spring 20054 Modification for Mode II Operation We can use our work for Mode 2 as well as Mode 1 if we make some additional modifications…

5. EE631 – Spring 20055 Modification for Mode II Operation Solution approach

6. EE631 – Spring 20056 Modification for Mode II Operation

7. EE631 – Spring 20057 Modification for Mode II Operation Thus, the effective firing angle must obey

8. EE631 – Spring 20058 Numerical Example Consider a system with a 560 V l-l rms voltage source, 20 mH commutating inductance, and operating at 60 Hz Let’s look at the output characteristics as dc link current varied from 0 to 100 A

9. EE631 – Spring 20059 Operating Mode

10. EE631 – Spring 200510 Output Voltage

11. EE631 – Spring 200511 Commutation Angle

12. EE631 – Spring 200512 Effective Firing Angle

13. EE631 – Spring 200513 Calculation of AC Currents Let’s consider the current in the generation source reference frame, i.e. the reference frame wherein

14. EE631 – Spring 200514 General Approach The average q- and d-axis current may be expressed

15. EE631 – Spring 200515 Commutation and Conduction Components Breaking the integrals up we have where

16. EE631 – Spring 200516 Calculation of Commutation Component We start with

17. EE631 – Spring 200517 Calculation of Commutation Component

18. EE631 – Spring 200518 Calculation of Commutation Component

19. EE631 – Spring 200519 Calculation of Commutation Component Finally, we arrive at (11.5-53) (11.5-54)

20. EE631 – Spring 200520 Calculation of Conduction Component During the conduction interval

21. EE631 – Spring 200521 Calculation of Conduction Component

22. EE631 – Spring 200522 Calculation of Conduction Component

23. EE631 – Spring 200523 Calculation of Conduction Component Thus we arrive at (11.5-55) (11.5-56)