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

2. Single Phase Full wave Voltage Controller with RL-Load

3. AC Voltage Controller-Output Voltage and Current with RL-Load
Case 1: Discontinuous Output Current
During the positive half cycle of the AC input voltage, T1 triggered at t = .
At t = , the voltage becomes zero but the current is not zero.
T1 will continue to conduct with current in the same direction but voltage negative.
At t = ; <(+ ) the load current becomes zero and T1 turned OFF
 - Current extinction angle.
At t = (+ ), T2 is triggered

4. Analysis
When T1 is triggered ON, the circuit equation is

5. Analysis AT t=, i(t) = 0; so that
The current extinction angle can be obtained by solving this transcendental equation using iterative method.
When  >, current attains zero at some instant. Hence the output current is discontinuous when the thyristor firing angle is greater than the load impedance angle.
The rms value of the output is

6. AC Voltage Controller-Output Voltage and Current with RL-Load
Case 2:  = 
T1 turned ON at t = . When  =  the equation for current becomes
The output current is purely sinusoidal. At t =  + , the current becomes zero, T1 is commuted here and T2 turned ON.

7. AC Voltage Controller-Output Voltage and Current with RL-Load

8. AC Voltage Controller-Output Voltage and Current with RL-Load

9. AC Voltage Controller-Using TRIAC

10. AC Voltage Controller-Using TRIAC –R-Load