GATE EE 2024 Set 1 — Question 28
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Power Electronics → Harmonics & AC-AC Converters → AC Voltage Controllers
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Question
A single-phase triac based AC voltage controller feeds a series RL load. The input AC supply is 230 V, 50 Hz. The values of R and L are 10 and 18.37 mH, respectively. The minimum triggering angle of the triac to obtain controllable output voltage is
Correct answer
(B) 30°
Solution
The given parameters are:
Resistance
Inductance
Supply frequency First, calculate the angular frequency :
Next, calculate the inductive reactance :
For a series RL load, the impedance angle is given by:
For a triac-based AC voltage controller feeding an RL load, the minimum triggering angle (also known as the extinction angle or firing angle limit) to obtain controllable output voltage is equal to the impedance angle of the load. If the triggering angle is less than , the triac will not turn on until the voltage across it reaches a certain level, which is effectively .Therefore, the minimum triggering angle is .The final answer is .
Resistance
Inductance
Supply frequency First, calculate the angular frequency :
Next, calculate the inductive reactance :
For a series RL load, the impedance angle is given by:
For a triac-based AC voltage controller feeding an RL load, the minimum triggering angle (also known as the extinction angle or firing angle limit) to obtain controllable output voltage is equal to the impedance angle of the load. If the triggering angle is less than , the triac will not turn on until the voltage across it reaches a certain level, which is effectively .Therefore, the minimum triggering angle is .The final answer is .
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