Electronics and Communication Engineering - Power Electronics

26. 

To protect an SCR against high di/dt we connect

A. a capacitance in series with SCR
B. a capacitance in parallel with SCR
C. an inductance in parallel with SCR
D. an inductance in series with SCR

Answer: Option D

Explanation:

current through inductance cannot change instantaneously.


27. 

In a parallel inverter

A. the commutating capacitor C is across the primary of transformer and the load is across the secondary
B. the commutating capacitor and load are connected across the secondary of transformer
C. the commutating capacitor C and load are connected in series and the combination is across the secondary of transformer
D. none of the above

Answer: Option A

Explanation:

No answer description available for this question. Let us discuss.

28. 

A silicon controlled switch has :

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

Answer: Option C

Explanation:

Anode, cathode, anode gate and cathode gate.


29. 

A dc chopper V = 500 V feeds an electric fraction dc series motor. The chopping frequency is 400 Hz. The series inductance required to limit the maximum current swing to 10 A is

A. 20 mH
B. about 31 mH
C. about 51 mH
D. about 92 mH

Answer: Option B

Explanation:

.


30. 

A single phase fully controlled bridge rectifier is fed by a source having inductance. The output voltage during overlap period is

A. Vm
B. 0.5 Vm
C. zero
D. 0.5 Vm - voltage drop across inductance

Answer: Option C

Explanation:

During the period of overlap all the four thyristors conduct and load is effectively short-circuited. Output voltage is zero.