Power Electronics - Section 9

In a semi converter feeding a resistive load

A. the waveshapes of output voltage and output current are exactly similar
B. the waveshapes of output voltage and output current can not be similar
C. the waveshapes of output voltage and output current are similar only for low values of firing angle
D. the waveshapes of output voltage and output current may be similar or dissimilar

A

In a 3 phase semiconverter, the output voltage becomes discontinuous for

A. firing angle > 30°
B. firing angle > 60°
C. firing angle > 90°
D. firing angle > 120°

B

In integral cycle control of ac regulator, the input power factor is equal to

A. duty cycle a
B. a^2
C. SQRTa
D. (a)^1/3

C

McMurrary full bridge inverter uses

A. auxiliary commutation
B. complementary commutation
C. natural commutation
D. any of the above

A

A fully controlled bridge converter feeds a highly inductive load such that the load current can be assumed to be constant. The wave shape of input current is

A. dc
B. sinusoidal
C. rectangular
D. none of the above

C

A static excitation system uses

A. transformer and thyristors
B. transformer and ac exciter
C. dc exciter and ac exciter
D. transformer and dc exciter

A

The application of gate signal decreases the break over voltage of on SCR.

A. True
B. False

A

The power factor at the input terminals of a cyclo- converter is generally

A. low and leading
B. low and lagging
C. high and leading
D. high and lagging

B

Modified Mc Murray full bridge inverter uses

A. 4 thyristors and 2 diodes
B. 4 thyristors and 4 diodes
C. 8 thyristors and 4 diodes
D. 8 thyristors and 8 diodes

D

Assertion (A): Gate triggering is the most commonly used method for triggering of an SCR.

Reason (R): Even a small gate current is sufficient to turn on an SCR.

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

A