Electronics and Communication Engineering - Power Electronics

46. 

Assertion (A): A high dv/dt may cause triggering of a thyristor.

Reason (R): A high dv/dt results in charging current in the thyristor.

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:

The charging current may cause triggering.


47. 

Assertion (A): When an SCR is conducting, the voltage drop across is about 1 V.

Reason (R): When an SCR is conducting, the junction temperature is about 200°C.

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 C

Explanation:

Junction temperature is about 120°C. Hence R is wrong.


48. 

When the core of a saturable reactor is saturated, the inductance is high.

A. True
B. False

Answer: Option B

Explanation:

Since core is saturated, change of flux is small and inductance is low.


49. 

In controlled heating circuits, thyristors act as

A. rectifier
B. inverter
C. ac regulator
D. chopper

Answer: Option C

Explanation:

The output voltage is controlled ac.


50. 

In a fully controlled bridge converter feeding a resistive load the waveshapes of output voltage and output current

A. are always similar
B. can never be similar
C. may be similar or dissimilar
D. are similar only if a = 0

Answer: Option A

Explanation:

For resistive load output current is always proportional to output voltage.


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