Electronics and Communication Engineering - Power Electronics

26. 

Current derating may be necessary when thyristors are operating in

A. series
B. parallel
C. series or parallel
D. none of the above

Answer: Option B

Explanation:

Since current does not divide equally, current derating is necessary.


27. 

If duty cycle is a and the load is a resistance R, the rms value of output voltage is

A. aV
B. a V
C. a2V
D.

Answer: Option B

Explanation:

RMS output voltage

VL = a V.


28. 

For a BJT a = 0.98, then β =

A. 0.02
B. 0.5
C. 4.9
D. 49

Answer: Option D

Explanation:


29. 

Assertion (A): Power transistor has lower switching time than SCR

Reason (R): Power transistor has greater switching time than SCR

A. Both A and R are correct and R is correct explanation of A
B. Both A and R correct but R is not correct explanation of A
C. A is correct but R is wrong
D. A is wrong but R is correct

Answer: Option D

Explanation:

Power transistor does not have high rating.


30. 

A 3 kV circuit uses SCR of 800 V rating. If derating is 25%, the number of SCRs in series is

A. 4
B. 5
C. 6
D. 8

Answer: Option B

Explanation:

.