Electronics and Communication Engineering - Power Electronics

21. 

The number of doped regions in a SCR is

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

Answer: Option C

Explanation:

p = n = p = n.


22. 

All inverters use forced commutation.

A. True
B. False

Answer: Option B

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

Answer: Option B

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

Answer: Option B

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

Answer: Option B

Explanation:

Reactor is used only for circulating current mode.