# Electronics and Communication Engineering - Power Electronics

### Exercise :: Power Electronics - Section 2

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

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

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

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

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