Deck 8: Electrical Drives and Components

Question 1

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

A)True
B)False
C)none
D)all of the above

Answer 1

False

Question 2

What type of force handles for active torques?

A)Strong nuclear forces
B)Weak nuclear forces
C)Gravitational forces
D)Electrostatic forces

Answer 2

Gravitational forces

Question 3

Passive torques always oppose the motion of the driven machine.

A)True
B)False
C)none
D)all of the above

Answer 3

True

Question 4

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

A)Elevators
B)Rolling Mills
C)Fan load
D)Separately excited dc generator connected to the resistive load

Question 5

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

A)Load torque > Motor torque
B)Load torque <<<< Motor torque
C)Load torque = Motor torque
D)Load torque < Motor torque

Question 6

Choose the correct one. (* stands for multiplication, J represents the moment of inertia, w represents angular spee(D).

A)J*d(w)/dt = Load torque - Motor torque
B)J*d(w)/dt = Load torque + Motor torque
C)J*d(w)/dt = Motor torque - Load torque
D)J*d(w)/dt = Load torque * Motor torque

Question 7

In DC chopper, the waveform for input and output voltages is respectively __________

A)Discontinuous and Continuous
B)Continuous and Discontinuous
C)Both continuous
D)Both discontinuous

Question 8

A chopper behaves as a __________

A)DC equivalent of AC switching device
B)DC equivalent of AC transformer
C)DC equivalent of AC relay
D)AC equivalent of circuit breaker

Question 9

A DC chopper feeds an RLE load. If the value of E is increased by 20%, the current ripple ________

A)increases by 20%
B)decreases by 20%
C)increases only 20%
D)remains the same

Question 10

The conduction loss versus device current characteristic of a power MOSFET is best approximated by a ________

A)Straight line
B)Rectangular hyperbola
C)Parabola
D)Exponential decaying functions

Question 11

Which of the following device is NOT suitable for parallel operation?

A)MOSFET
B)BJT
C)IGBT
D)TRIAC

Question 12

SCR is uni-directional in nature.

A)True
B)False
C)none
D)all of the above

Question 13

Which of the following device should be used as a switch in a low power switched mode power supply (SMPS)?

A)GTO
B)BJT
C)MOSFET
D)TRIAC

Question 14

Servo motors are an example of which type of load?

A)Pulsating loads
B)Short time loads
C)Impact loads
D)Short time intermittent loads

Question 15

Load torque of the crane is independent of _________

A)Speed
B)Seebeck effect
C)Hall effect
D)Thomson effect

Question 16

The unit of angular velocity is rad/s .

A)True
B)False
C)none
D)all of the above

Question 17

R.M.S value of the sinusoidal waveform V=V sin(?t+?).

A)V ÷2
B)V ÷2.
C)V ÷2..
D)V ÷3

Question 18

Calculate the time period of the waveform x(t)=24sin(24?t+?÷4).

A)064 sec
B)047 sec
C)083 sec
D)015 sec

Question 19

The turn-o times of the devices in increasing order is ___________
I. MOSFET
II. BJT
III. IGBT
IV. Thyristor

A)I, III, II, IV
B)I, II, III, IV
C)III, I, II, IV
D)III, II, IV, I

Question 20

Which of the following devices should be used as a switch for high power and high voltage application?

A)GTO
B)MOSFET
C)TRIAC
D)Thyristor

Question 21

Calculate the useful power developed by a motor using the given data: P = 3000 W, I = 60 A, R = .4 ?. Assume frictional losses are 200 W and windage losses are 400 W.

A)970 W
B)960 W
C)980 W
D)990 W

Question 22

The consideration involved in the selection of the type of electric drive for a particular application depends on

A)Speed control range and its nature
B)Starting torque
C)Environmental conditions
D)All of the above.

Question 23

Which of the following is preferred for automatic drives ?

A)Synchronous motors
B)Squirrel cage induction motor
C)Ward Leonard controlled dc motors

Question 24

The motor normally used for crane travel is

A)AC slip ring motor
B)Ward Leonard controlled DC shunt motor
C)Synchronous motor
D)DC differentially compound motor.