Electrical Drives And Controls Set 9 MCQs

Q1 | Full form of THD is

total harmonic diverter

total harmonic digital

total harmonic distortion

total harmonic discrete

Q2 | Calculate the compensator rating required for a sec(Φ)=1.

0.64 p.u

0.21 p.u

0.57 p.u

0 p.u

Q3 | Calculate the value of Voltage ripple factor if the Form factor is 1.1.

45.8 %

46.2 %

47.5 %

49.9 %

Q4 | Calculate the value of THD if the distortion factor is .8.

76 %

75 %

74 %

73 %

Q5 | Full form of VRF.

voltage ripple factor

voltage revert factor

volume ripple factor

volume revert factor

Q6 | Second lowest order harmonic present in 3-Φ fully controlled rectifier is

5th

7th

3rd

2nd

Q7 | The flux and the internally generated voltage of a dc machine is a function of its magneto-motive force.

non-linear

linear

constant

inverse

Q8 | Choose the best option which identifies about the below characteristics.

(1)series motor (2) cumulative compound motor (3) shunt motor

(1)cumulative compound motor (2) series motor (3) shunt motor

(1)cumulative compound motor (2) shunt motor (3) series motor

(1)shunt motor (2) series motor (3) cumulative compound motor

Q9 | The speed torque of the differential compound dc motor is shown below. What conclusions can be made?

this is an unstable machine

there is regenerative increment in the speed

this is impractical to be used

all of the mentioned

Q10 | It is impossible to start a differential compounded dc motor.

true

false

Q11 | A student is given a differential compound motor and he has been asked to make it start. How will he try?

by shorting series field at start

to run as shunt motor at start

by making rated current at start

all of the mentioned

Q12 | For a 100 hp 250 V, compound dc motor with compensating winding has a field current of 5 A to produce a voltage of 250 V at 1200 rpm. What will be the shunt field current of this machine at no load?

5 a

5.6 a

4 a

0 a

Q13 | Load torques can be classified into how many types?

three

two

four

five

Q14 | Rolling mills exhibit what type of load torque characteristics?

constant torque characteristics

linearly rising torque characteristics

non-linearly rising torque characteristics

non-linearly decreasing torque characteristics

Q15 | What is the relationship between torque and speed in constant type loads?

torque is independent of speed

torque linearly increases with increase in speed

torque non-linearly increases with an increase in speed

torque non-linearly decreases with an increase in speed

Q16 | Torque inversely varies with the speed in the windage load torque component.

true

false

Q17 | What type of force handles for active torques?

strong nuclear forces

weak nuclear forces

gravitational forces

electrostatic forces

Q18 | Passive torques always oppose the motion of the driven machine.

true

false

Q19 | Among the following which one exhibits linearly rising load torque characteristics?

elevators

rolling mills

fan load

separately excited dc generator connected to the resistive load

Q20 | What is the condition for the steady-state operation of the motor?

load torque > motor torque

load torque <<<< motor torque

load torque = motor torque

load torque < motor torque

Q21 | Choose the correct one. (* stands for multiplication, J represents the moment of inertia, w represents angular speed).

j*d(w)/dt = load torque – motor torque

j*d(w)/dt = load torque + motor torque

j*d(w)/dt = motor torque – load torque

j*d(w)/dt = load torque * motor torque

Q22 | Which of the following is the best braking method?

friction

electromechanical action

eddy-currents

electric braking

Q23 | DC motor is still widely used in tractions due to its excellent braking properties.

true

false

Q24 | Which of the following is not the method of electrical braking?

plugging or counter-current

dynamic or rheostatic

regenerative

eddy current

Q25 | Which of the following is the plugging method of braking?

reversal of field connections

reversal of armature connections

addition of equal and opposite field

removal of field circuit from current machine circuit