# Electronics and Communication Engineering - Power Electronics

### Exercise :: Power Electronics - Section 2

21.

The number of doped regions in a SCR is

 A. 2 B. 3 C. 4 D. 5

Explanation:

p = n = p = n.

22.

All inverters use forced commutation.

 A. True B. False

Explanation:

Line commutated inverters are also used especially in HVDC.

23.

In 180° mode of operation of a 3 phase bridge inverter, two thyristors conduct at one time.

 A. True B. False

Explanation:

In 180° mode three thyristors conduct simultaneously.

24.

In a single phase full wave ac regulator the rms value of load current is 20 A load is purely resistive. Then

 A. average thyristor current will be less than 20 A but rms thyristor current will be more than 20 A B. both the average and rms thyristor currents will be less than 20 A C. both the average and rms thyristor currents will be more than 20 A D. rms thyristor current will be 20 A and average thyristor current will be 10 A

Explanation:

Each thyristor conducts for 50% of time.

25.

A reactor is used in a dual converter operating in non-circulating current mode.

 A. True B. False