Electronics and Communication Engineering - Power Electronics - Discussion


An SCR is triggered at 40° in the positive half cycle only. The average anode current is 50 A. If the firing angle is changed to 80°, the average anode current is likely to be

[A]. 50 A
[B]. 25 A
[C]. less than 50 A but more than 25 A
[D]. less than 25 A

Answer: Option C



Rupesh9292 said: (May 19, 2015)  
Please justify.

Vamsi said: (Dec 5, 2016)  
Please explain it in clear.

Hanu said: (Feb 9, 2018)  
Explain it clearly.

Vivek Yadav said: (Feb 16, 2018)  
i for 80/i for 40=0.66,
given i for 40 = 50,
then i for 80=50*0.66=33 A so option c is correct.

Jiaac said: (Sep 19, 2019)  
Since Vm is constant for the two cases, the ratio can be written as:
(1+cos40°)/(1+cos80°) = 50A/X.

Solve for X, and you get the average anode current of 33.23A for 80° firing angle.

Since 33.23A is less than 50A but more than 25A, option C is correct.

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