#### 29) A half controlled converter can operate in how many quadrants of V-I plane?

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

#### 31) A 220 v , 960 rpm, 10A separately excited DC motor has an armature resistance of 2$\Omega$. It is fed from a SP-SC-FWR with an input AC supply of single phase 230 V rms, and 50 Hz. If the triggering angle $\alpha = 60^o$, the no load speed of the motor is

a. 960 rpm

b. 1029 rpm

c. 1423 rpm

d. 1561 rpm

#### 32) If the triggering angle $\alpha = 120^o$ for Q31, the no-load speed of the motor is

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. $6 f$

#### 35) A three phase fully-controlled rectifier is fed from three-phase, 400 V 50 $H_Z$ AC supply. If the triggering angle of the converter is $45^o$, the average output DC voltage is

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 $\alpha$.

#### 37) A class A two-quadrant chopper operates in which quadrants of V-I plane?

a. 1 & 2

b. 2 & 3

c. 3 & 4

d. 4 & 1

#### 38) A 230 V , 900 rpm, 200 A separately excited DC motor has an armature resistance of 0.05 $\Omega$. The motor is fed from a two quadrant chopper which provides motoring and regenerative braking operation. The source has a voltage of 200 VDC. Assuming continuous conduction , calculate the duty cycle of the chopper for operation at rated torque and speed of 500 rpm.

a. 0.54

b. 0.44

c. 0.34

d. 0.24

#### 39) The motor in Q38 is operated in regenerative braking mode with rated torque and speed of 600 rpm. Calculate the duty cycle of the switch.

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