## Question Set 3

a. One

b. Two

c. Three

d. Four

#### 30) For a semi-controlled rectifier, the duration $\pi \lt \omega t \lt \beta$ is known as

a. Duty Interval

b. Coasting Interval

c. Freewheeling Interval

d. Zero-Current Interval

a. 960 rpm

b. 1029 rpm

c. 1423 rpm

d. 1561 rpm

a. 960 rpm

b. 1051 rpm

c. 1352 rpm

d. 1529 rpm

#### 33) A SP-FC-FWR is used to control the armature of a separately excited DC motor. The critical speed which separates continuous and discontinuous current operation is found out to be 720 rpm. Which of the following statements is correct?

a. The converter operates in continuous current operation for speed greater than 720 rpm

b. The converter operates in continuous current operation for speed less than 720 rpm

c. The converter operates in continuous current operation for speed greater than 360 rpm

d. The converter operates in continuous current operation for speed less than 360 rpm

#### 34) If the AC input supply frequency is $f$ , the ripple frequency of the output voltage of a three-phase fully controlled rectifeir is

a. $f$

b. $2 f$

c. $3 f$

d. $6 f$

a. 231. 1 V

b. 305.6 V

c. 381.9 V

d. 421.7 V

#### 36) A three-phase fully-controlled rectifier is feeding the armature of a separately excited DC motor. The motor has to operate in quadrant III. Which of the following methods is suitable?

a. By adjusting the triggering angle $\alpha$ only.

b. By adjusting the triggering angle $\alpha$ followed by armature connection reversal.

c. By operating with triggering angle $\alpha \gt 90^o$.

d. By connecting a freewheeling diode across the armature in addition to adjusting the triggering angle $\alpha$.

a. 1 & 2

b. 2 & 3

c. 3 & 4

d. 4 & 1

a. 0.54

b. 0.44

c. 0.34

d. 0.24

a. 0.29

b. 0.39

c. 0.49

d. 0.59

#### 40) Assuming continuous current operation for a single quadrant chopper used for motoring operation of a DC motor, what is the interval $t_{on} \lt t \lt T$ called?

a. Duty interval

b. Freewheeling interval

c. Coasting interval

d. Energy storage interval