Electronics and Communication Engineering - Power Electronics

36. 

The rated current of a thyristor is 40 A. The holding current will be about :

A. 20 A
B. 1 A
C. 100 mA
D. 10 mA

Answer: Option D

Explanation:

The holding current is much less then 1% of rated current.


37. 

A cycloconverter is

A. ac-dc converter
B. dc-ac converter
C. dc-dc converter
D. ac-ac converter

Answer: Option D

Explanation:

It changes ac at frequency f into ac at a frequency different from f.


38. 

The number of leads in a power semiconductor diode are

A. 2
B. 3
C. 4
D. 2 or 3

Answer: Option A

Explanation:

A diode has 2 leads irrespective of its rating.


39. 

If ton and toff are the turn on and turn off times of a thyristor, then

A. ton and toff are almost equal
B. ton >> toff
C. toff >> ton
D. ton is about twice toff

Answer: Option C

Explanation:

Turn on time is less than 3 μs while turn off time is between 10-300 μs.


40. 

Assertion (A): The gate current of an SCR is always in the form of pulses.

Reason (R): The gate losses, in pulse triggering, are low.

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 A

Explanation:

Gate current in the form of pulses is commonly used because gate losses are low.