1. Dr. Unnikrishnan P.C. Professor, EEE
EE305 Power Electronics
Dr. Unnikrishnan P.C.
Professor, EEE

2. Sequence Control (two stage) with R load
The turns ratio from primary to each secondary is taken as 1 for convenience
The source voltage, vS
Output Voltage Control from zero to rms value V:
Use only T3 and T4.
For output voltage=0: =180
For output voltage=V: =0
Output Voltage Control from V to 2V: Use only T1 and T2 &  for thyristor pair T3,T4 is always zero.  for T1,T2 varied from 0 to 180

3. Sequence Control (two stage) with R load
T3 triggered at t = 0 and T4 at t = 
T1 triggered at t =  and T2 at t = + 

4. Sequence Control (two stage) with R load

5. Sequence Control (two stage) with R load

6. Sequence Control (two stage) with R load

7. Sequence Control (two stage) with R load

8. Sequence Control (two stage) with R load

9. Sequence Control (two stage) with R load

10. Advantages of two stage Sequence Control
Load Current is continuous and so load performance is better
Wider control of load voltage
Reduction of harmonics in the load and supply current
Disadvantages:
More complex firing circuitry
More expensive voltage controller